CN100550440C - The manufacture method of semiconductor element and semiconductor element - Google Patents
The manufacture method of semiconductor element and semiconductor element Download PDFInfo
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- CN100550440C CN100550440C CNB2005101185148A CN200510118514A CN100550440C CN 100550440 C CN100550440 C CN 100550440C CN B2005101185148 A CNB2005101185148 A CN B2005101185148A CN 200510118514 A CN200510118514 A CN 200510118514A CN 100550440 C CN100550440 C CN 100550440C
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Abstract
The invention provides a kind of technology, can improve the manufacturing of the semiconductor element that has utilized gallium nitride substrate (GaN substrate), on the GaN substrate, form flatness and the superior nitride-based semiconductor layer of crystallinity simultaneously.Preparing upper surface (10a) has more than or equal to 0.1 ° of gallium nitride substrate (10) smaller or equal to 1.0 ° deviation angle θ in＜1-100＞direction with respect to (0001) face.And, go up the stacked a plurality of nitride-based semiconductor layers that contain n type semiconductor layer (11) at the upper surface (10a) of GaN substrate (10), thus the semiconductor element of formation semiconductor laser etc.
Description
Technical field
The present invention relates to a kind of semiconductor element and manufacture method thereof that on gallium nitride (GaN) substrate, has the nitride-based semiconductor layer.
Background technology
The nitride-based semiconductor of gallium nitride etc. is utilized or studies as the electronic device of light-emitting component and other, utilizes its characteristic, and blue LED and green LED are practical.In addition, utilize nitride-based semiconductor, developing blue violet semiconductor laser as follow-on high density compact disc light source.
In the past, when making has utilized the light-emitting component of nitride-based semiconductor,, mainly used Sapphire Substrate as substrate., lattice rate of not matching of formed nitride-based semiconductor is about 13% very greatly on Sapphire Substrate and its, has the defective of dislocation etc. on this nitride-based semiconductor middle-high density ground, is difficult to obtain the nitride-based semiconductor of high-quality.
In addition, in recent years, developing the less gallium nitride substrate of defect concentration (being called " GaN substrate " later on), prevailing with the relevant research and development of method that utilize of GaN substrate.Proposition has and mainly utilizes the GaN substrate to be used as the semiconductor laser substrate.
Make nitride-based semiconductor under the situation of growing on the GaN substrate,, can not obtain the such problem of good crystallinity with regard to producing when making nitride-based semiconductor at the C face, when promptly growing on (0001) face.For this problem, in patent documentation 1, following technology has been proposed: the upper surface by making the GaN substrate with respect to the C face tilt more than or equal to 0.03 ° smaller or equal to 10 °, just can improve the crystallinity that is formed at the nitride-based semiconductor optical device on this GaN substrate, can realize long lifetime.
In addition, form the technology of semiconductor element, for example also be disclosed in the patent documentation 2,3 about utilizing nitride-based semiconductor.
Patent documentation 1: the spy opens the 2000-223743 communique
Patent documentation 2: the spy opens the 2000-82676 communique
Patent documentation 3: the spy opens the 2003-60318 communique
In addition, when utilizing the GaN substrate to form the semiconductor element of semiconductor laser etc., the crystallinity of wishing to be not only the nitride-based semiconductor layer that is formed on the GaN substrate is good, and its surperficial flatness is also good.But when the technology of utilizing patent documentation 1 was grown the nitride-based semiconductor layer on the GaN substrate, the flatness on the surface of this nitride-based semiconductor layer was insufficient, and then can not fully guarantee its crystallinity.Therefore, when utilizing this nitride-based semiconductor layer to form semiconductor element, there is the problem that its electrical characteristics worsen or the reliability reduction is such.In addition, from the viewpoint of the manufacturing of semiconductor element, the upper surface of not wishing to make the GaN substrate is crustal inclination largely.
Summary of the invention
Therefore, the present invention proposes in view of the above-mentioned problems, and its purpose is to provide a kind of technology, can improve the manufacturing of the semiconductor element that has utilized the GaN substrate, forms flatness and the superior nitride-based semiconductor layer of crystallinity simultaneously on the GaN substrate.
The nitride-based semiconductor layer that semiconductor element of the present invention has the gallium nitride substrate and forms on the upper surface of above-mentioned gallium nitride substrate, the above-mentioned upper surface of above-mentioned gallium nitride substrate with respect to (0001) face at＜1-100 direction has more than or equal to 0.1 ° of deviation angle (off angle) smaller or equal to 1.0 °.
In addition, the manufacture method of semiconductor element of the present invention has following operation: operation (a) prepare upper surface with respect to (0001) face at＜1-100 direction has more than or equal to 0.1 ° of gallium nitride substrate smaller or equal to 1.0 ° deviation angle; And operation (b) forms the nitride-based semiconductor layer on the above-mentioned upper surface of above-mentioned gallium nitride substrate.
Manufacture method according to semiconductor element of the present invention and semiconductor element, because the upper surface of gallium nitride substrate with respect to (0001) face at＜1-100 direction has more than or equal to 0.1 ° of deviation angle smaller or equal to 1.0 °, so can improve the manufacturing of semiconductor element of the present invention, on the gallium nitride substrate, form flatness and the superior nitride-based semiconductor layer of crystallinity simultaneously.
Description of drawings
Fig. 1 is the stereogram of structure of the gallium nitride substrate of expression embodiment of the present invention.
Fig. 2 is the stereogram of structure of the semiconductor element of expression embodiment of the present invention.
Fig. 3 is the stereogram of variation of structure of the semiconductor element of expression embodiment of the present invention.
Fig. 4 is the flow chart of manufacture method of the semiconductor element of expression embodiment of the present invention.
Fig. 5 be illustrated in the gallium nitride substrate upper surface deviation angle and at the figure of the relation of the highest elevation difference on the surface of nitride-based semiconductor layer.
Fig. 6 is that the upper surface of expression gallium nitride substrate is at＜1-100〉when direction has deviation angle,＜11-20 direction deviation angle and at the figure of the relation of the highest elevation difference of the upper surface of nitride-based semiconductor layer.
Fig. 7 is the stereogram of variation of structure of the semiconductor element of embodiment of the present invention.
Fig. 8 is expression to the heat treatment time of gallium nitride substrate with at the figure of the relation of the highest elevation difference of the upper surface of this gallium nitride substrate.
Fig. 9 is expression to the heat treatment temperature of gallium nitride substrate with at the figure of the relation of the highest elevation difference of the upper surface of this gallium nitride substrate.
Figure 10 is the impurity concentration of expression nitride-based semiconductor layer and at the figure of the relation of the highest elevation difference of the upper surface of this nitride-based semiconductor layer.
Embodiment
Fig. 1 is the stereogram of structure of the GaN substrate 10 of expression embodiment of the present invention.The GaN substrate 10 of present embodiment has the crystalline texture of hexagonal crystal system, utilizes this GaN substrate 10, forms the semiconductor element of the light-emitting component, high-frequency electron device etc. of semiconductor laser and light-emitting diode etc.
As shown in Figure 1, the upper surface 10a of GaN substrate 10 is with respect to the C face, promptly (0001) face is at＜1-100〉direction has deviation angle θ.Therefore, the upper surface 10a of GaN substrate 10 with＜1-100 the vertical and＜11-20 parallel of direction with the C face direction be rotating shaft, will be parallel with the C face the face that obtains of face rotation deviation angle θ parallel.In the present embodiment, deviation angle θ is set at more than or equal to 0.1 ° smaller or equal to 1.0 °.
The GaN substrate 10 that comprises present embodiment, as shown in Figure 1, general at the surface of GaN substrate, edge＜11-20〉direction alternately is arranged with dislocation density higher zone 21 and the lower zone 22 of dislocation density.When utilizing this GaN substrate to form semiconductor element, normally utilize the lower zone of dislocation density 22.
Below, an example of the semiconductor element that forms at utilizing GaN substrate 10 describes.Fig. 2 is that expression utilizes GaN substrate 10 and the stereogram of the structure of the nitride-based semiconductor laser device that forms.As shown in Figure 2, stacked a plurality of nitride-based semiconductor layers on the upper surface 10a of GaN substrate 10.Specifically, n type semiconductor layer 11, n type coating layer 12, n type photoconductive layer 13, multiple quantum trap (MQW) active layer 14, p type electron barrier layer 15, p type photoconductive layer 16, p type coating layer 17, p type contact layer 18 on the upper surface 10a of GaN substrate 10, have been stacked gradually.And, being provided with n electrode 19 at the lower surface of GaN substrate 10, the upper surface of p type contact layer 18 is provided with p electrode 20.
N type semiconductor layer 11 for example is aluminum gallium nitride (AlGaN) formation of GaN 1.0 μ m, the n type or n type by thickness.N type coating layer 12 is Al 1.0 μ m, the n type by thickness for example
0.07Ga
0.93N constitutes.N type photoconductive layer 13 is that GaN 0.1 μ m, the n type constitutes by thickness for example.Multiple quantum trap active layer 14 has for example by InGaN (In
0.12Ga
0.88N) thickness of Gou Chenging is the trap layer of 3.5nm and is the alternately laminated multiple quantum trap structure of barrier layer of 7.0nm by the thickness that GaN constitutes.
P type electron barrier layer 15 is Al 0.02 μ m, the p type by thickness for example
0.2Ga
0.8N constitutes.P type photoconductive layer 16 is that GaN 0.1 μ m, the p type constitutes by thickness for example.P type coating layer 17 is Al 0.4 μ m, the p type by thickness for example
0.07Ga
0.93N constitutes.And p type contact layer 18 is that GaN 0.1 μ m, the p type constitutes by thickness.
The nitride-based semiconductor laser device of present embodiment with this structure is at＜1-100〉face dissociates, this＜1-100 mask has resonator mirror.And, when between n electrode 19 and p electrode 20, applying voltage, from multiple quantum trap active layer 14 output laser.
Fig. 3 is the stereogram of variation of structure of the semiconductor laser of expression present embodiment.Semiconductor laser shown in Figure 3 is the semiconductor laser of carinate guided wave type, in semiconductor laser shown in Figure 1, changes the shape of p type coating layer 17, p type contact layer 18 and p electrode 20, also has silicon oxide layer 52.Below, describe at the manufacture method of semiconductor laser shown in Figure 3.
In addition, in the crystalline growth method of the nitride-based semiconductor layer of n type semiconductor layer 11, n type coating layer 12 etc., there are organic metal vapor deposition (mocvd method), molecular beam epitaxy (MBE method), hydride gas phase epitaxial growth method (HVPE) etc., in the example below, use mocvd method.In III family raw material, use trimethyl gallium (hereinafter referred to as " TMG "), trimethyl aluminium (hereinafter referred to as " TMA ") or trimethyl indium (hereinafter referred to as " TMI "), in V family raw material, use ammonia (NH
3) gas.In addition, in n type impurity raw material, for example use silane (SiH
4), in p type impurity raw material, for example use two luxuriant magnesium (CP
2Mg).And, in the carrier gas of these unstrpped gases of delivery, use hydrogen (H
2) gas and nitrogen (N
2).
Fig. 4 is the flow chart of the manufacture method of expression semiconductor laser shown in Figure 3.At first, in step s1, for example preparing, deviation angle θ is set at 0.5 ° GaN substrate 10 shown in Figure 1.And, in step s2, GaN substrate 10 is heat-treated.In step s2, at first GaN substrate 10 is arranged in the MOCVD device.Then, in device, supply with NH
3Gas, and the temperature in will installing is warmed up to 1000 ℃.After the intensification, in device, supply with and contain NH
3Gas, N
2Gas and H
2The mixed gas of gas in this mixed-gas environment, was heat-treated 15 minutes GaN substrate 10.At this moment, H in mixed gas
2The shared ratio of gas for example is set at 5%.
Then, in step s 3, the stacked a plurality of nitride-based semiconductor layers that contain n type semiconductor layer 11 grades on GaN substrate 10.In step s3, at first, TMG gas and SiH are supplied with in beginning in the MOCVD device
4Gas is grown the n type semiconductor layer 11 that is made of n type GaN on the upper surface 10a of GaN substrate 10.And, and then begin to supply with TMA gas, make Al by the n type
0.07Ga
0.93The n type coating layer 12 that N constitutes is grown on n type semiconductor layer 11.
Then, stop to supply with TMA gas, the n type photoconductive layer 13 that the GaN by the n type is constituted is grown on n type coating layer 12.Stop to supply with TMG gas and SiH thereafter,
4Gas is with the greenhouse cooling to 700 ℃ in the device.Then, multiple quantum trap active layer 14 is grown on n type photoconductive layer 13.Specifically, by supplying with TMG gas, TMI gas and NH
3Gas, growth is by In
0.12Ga
0.88The trap layer that N constitutes is by supplying with TMG gas and NH
3Gas, the barrier layer that growth is made of GaN.By carrying out this processing repeatedly, formation has 3 pairs the trap layer and the right multiple quantum trap active layer 14 of barrier layer.
Supply with NH thereafter,
3After temperature in will installing in the time of gas is warmed up to 1000 ℃ again, begin to supply with TMG gas, TMA gas, CP
2Mg gas makes the Al by the p type
0.2Ga
0.8The p type electron barrier layer 15 that N constitutes is grown on multiple quantum trap active layer 14.Then, stop to supply with TMA gas, the p type photoconductive layer 16 that the GaN by the p type is constituted is grown on p type electron barrier layer 15.Then, begin once more to supply with TMA gas, make Al by the p type
0.07Ga
0.93The thickness that N constitutes is that the p type coating layer 17 of 0.4 μ m is grown on p type photoconductive layer 16.
Then, stop to supply with TMA gas, the thickness that the GaN by the p type is constituted is that the p type contact layer 18 of 0.1 μ m is grown on p type coating layer 17.Stop to supply with TMG gas and CP thereafter,
2Mg gas is with the temperature cool to room temperature in the device.
As above, when the crystalline growth of all nitride-based semiconductor layers finishes, when step s3 finishes, in step s4, becomes the spine 51 of light-guide wave path.In step s4, at first, on entire wafer, apply resist, carry out photo-mask process, thereby form resist figure corresponding to the regulation shape of table top portion shape.This resist figure as mask, is for example passed through reactive ion etching (RIE) method, etching p type contact layer 18 and p type coating layer 17 successively.Thus, become the spine 51 of light-guide wave path.In addition, as the etching gas of this moment, for example using chlorine is gas.
Then, in step s5, form p electrode 20 and n electrode 19.In step s5, at first, residual the resist figure that uses as mask in step s4 utilizes CVD method, vacuum vapour deposition or metallikon etc., and for example forming on entire wafer, thickness is the silicon oxide film (SiO of 0.2 μ m
2Film) 52, when removing resist pattern, remove the silicon oxide film 52 that is in the spine 51.This processing is called as " peeling off (lift-off) ".Thus, the peristome 53 of spine 51 is exposed in formation on silicon oxide film 52.
Then, after for example forming metal film that constitutes by platinum (Pt) and the metal film that constitutes by gold (Au) on the entire wafer successively, carry out resist working procedure of coating and photo-mask process, afterwards by vacuum vapour deposition, carry out wet etching or dry etching, thereby in peristome 53, form p electrode 20.
Afterwards,, for example form metal film that constitutes by titanium (Ti) and the metal film that constitutes by aluminium (Al) successively, formed stacked film is carried out etching form n electrode 19 by vacuum vapour deposition at the lower surface of whole GaN substrate 10.And, be used to make the fuse process of n electrode 19 ohmic contact to GaN substrate 10.
Top formed structure is processed into strip by dissociating etc., forms two resonator end faces in this structure.And, these resonator end faces have been implemented end face coating after, this list structure is divided into shaped like chips by dissociating etc.Thus, finish semiconductor laser shown in Figure 3.
As above, in the present embodiment, because the upper surface 10a of GaN substrate 10 with respect to (0001) face at＜1-100 direction has the deviation angle θ more than or equal to 0.1 °, so the flatness of formed n type semiconductor layer 11 and crystallinity improve on this upper surface 10a.Consequently, utilize n type semiconductor layer 11 and the electrical characteristics of the semiconductor element of the present embodiment that forms improve, reliability improves.
Fig. 5 be expression GaN substrate 10 upper surface 10a deviation angle θ and at the figure of the relation of the highest elevation difference of the upper surface that is formed at the n type semiconductor layer 11 on this upper surface 10a.Diamond symbols among Fig. 5 is that the upper surface 10a of GaN substrate 10 as present embodiment is at＜1-100〉data when direction has deviation angle θ, square symbols is different with present embodiment, and the upper surface 10a that is GaN substrate 10 is at＜11-20〉data when direction has deviation angle θ.Diamond symbols among described Fig. 9 in back, 10 and square symbols also are same.
In addition, to represent to make n type semiconductor layer 11 to grow into thickness be 4 μ m to the highest elevation difference of the longitudinal axis among Fig. 5, use the value of atomic force microscope (Atomic ForceMicroscopy:AFM) when the scope of vertical 200 μ m * horizontal 200 μ m is carried out surface observation to this n type semiconductor layer 11.To described Fig. 6 in back, 10 also is same.
As shown in Figure 5, when deviation angle θ is during more than or equal to 0.1 °, diminish significantly in the highest elevation difference of the upper surface of n type semiconductor layer 11, configuration of surface is good.And, at＜1-100〉under the situation of the upper surface 10a of direction inclination GaN substrate 10, when deviation angle θ is during more than or equal to 0.25 °, further reduce in the highest elevation difference of n type semiconductor layer 11, the configuration of surface of this n type semiconductor layer 11 is good.On the other hand, as shown in Figure 5, when deviation angle θ is bigger than 1.0 °, just become big in the highest elevation difference of the upper surface of n type semiconductor layer 11.
In addition, be during at deviation angle θ, because produce the hexagonal hillock, so, can not obtain smooth form in the concavo-convex increase on its surface on the surface of n type semiconductor layer 11 smaller or equal to 0.05 °.
In addition, at deviation angle θ more than or equal to 0.05 ° during less than 0.25 °, along the direction vertical with the direction of deviation angle θ, promptly with＜1-100 direction or＜11-20 the vertical direction of direction produces step-like jump.But, at the direction edge＜1-100 of deviation angle θ〉and under the situation of direction, when deviation angle θ is during more than or equal to 0.25 °, step-like jump reduces, and obtains more smooth form.At this moment, the average surface roughness in n type semiconductor layer 11 can be suppressed at smaller or equal to 0.5nm.
On the other hand, direction edge＜11-20 at deviation angle θ〉under the situation of direction, even deviation angle θ is more than or equal to 0.25 °, also because the higher zone 21 of lip-deep dislocation density of the GaN substrate 10 shown in Fig. 1, hinder step stream (step flow) growth, so step-like jump is residual, can not obtain the surface of good form.The following problem of concavo-convex generation on this surface: when the semiconductor laser of for example making as present embodiment, not only in n type semiconductor layer 11, and also producing jump at multiple quantum trap active layer 14, it is big that the loss in the resonator of laser becomes, threshold current density deterioration etc.
As described above, the deviation angle θ of the upper surface 10a of GaN substrate 10 and its direction are formed at the concave-convex surface and the bigger influence of crystallinity of the grown layer of this upper surface 10a.The picture present embodiment is at edge＜1-100〉direction tilted upper surface 10a more than or equal to 0.1 ° GaN substrate 10 when going up the making semiconductor laser, can obtain the good and stable element characteristic of flatness and crystallinity.And, at edge＜1-100〉the upper surface 10a that tilted more than or equal to 0.25 ° GaN substrate 10 of direction goes up when making semiconductor laser, it is better that flatness and crystallinity become, at edge＜1-100〉the upper surface 10a that tilted more than or equal to 0.3 ° GaN substrate 10 of direction goes up when making semiconductor laser, and flatness and crystallinity further improve.
And then, in the present embodiment because deviation angle θ is set at smaller or equal to 1.0 °, so processing GaN substrate 10 and the processability when deviation angle θ is set improve, and then, be formed on easily on the GaN substrate 10 stacked a plurality of nitride-based semiconductor layers.Therefore, utilized the manufacturing of the semiconductor element of GaN substrate 10 to improve.
In addition, at (1-100) of semiconductor laser mask resonator mirror is arranged usually, still, at this moment, as edge＜1-100〉when the deviation angle θ of direction became big, it is big that the speculum loss just becomes.Therefore, losing the also preferred deviation angle θ of this viewpoint from the speculum that is reduced in semiconductor laser is set in smaller or equal to 1.0 °.
In GaN substrate 10 shown in Figure 1, only at＜1-100〉direction is provided with deviation angle θ, but also can be at＜11-20 direction is provided with deviation angle θ 1.Fig. 6 is the upper surface 10a that is illustrated in GaN substrate 10 at＜1-100〉direction have 0.25 ° deviation angle θ and also at＜11-20 when direction has deviation angle θ 1, this deviation angle θ 1 and be formed at the figure of relation of highest elevation difference of the upper surface of the n type semiconductor layer 11 on this upper surface 10a.
As shown in Figure 6, at the upper surface 10a of GaN substrate 10 edge＜1-100〉direction tilts in 0.25 ° the state, as general＜11-20〉the deviation angle θ 1 of direction is set in more than or equal to 0 ° during smaller or equal to 0.1 °, highest elevation difference at the upper surface of n type semiconductor layer 11 changes hardly, and the configuration of surface of this n type semiconductor layer 11 is good.Result shown in Fig. 6 is the result of deviation angle θ when being 0.25 °,, if deviation angle θ is more than or equal to 0.25
° also be same result.In addition, Fig. 7 is illustrated in and has utilized in the nitride-based semiconductor laser device shown in Figure 2 respectively at＜1-100〉direction has deviation angle θ, at＜11-20 the structure of this nitride-based semiconductor laser device when direction has the GaN substrate 10 of deviation angle θ 1.
Fig. 8 is with the H in the mist
2The ratio of gas is illustrated in the growth furnace inherence as parameter and contains NH
3Gas, N
2Gas and H
2Gas or contain NH
3Gas and N
2When with 1000 ° GaN substrate 10 being heat-treated in the mixed-gas environment of gas, at the figure of the relation of the highest elevation difference of the upper surface 10a of GaN substrate 10 and heat treatment time.
Circle symbol among Fig. 8 is represented H
2The dividing potential drop of gas is 0% o'clock, is not contain H in the mist
2Data during gas, the square symbols among Fig. 8, triangle, fork symbol, * symbol and diamond symbols are represented H respectively
2The dividing potential drop of gas is set at 5%, 10%, 20%, 30% and 40% o'clock data.In addition, the highest elevation difference of the longitudinal axis among Fig. 8 represents to use the value of AFM when the scope of vertical 10 μ m * horizontal 10 μ m is carried out surface observation to the upper surface 10a of GaN substrate 10.To the described Fig. 9 in back also is same.
As shown in Figure 8, in above-mentioned step 2, work as H
2The dividing potential drop of gas is for smaller or equal to 30%, when carrying out more than or equal to 5 minutes heat treatment, and the concavo-convex of the upper surface 10a of GaN substrate 10 reduces largely.
In addition, pass through H
2The dividing potential drop of gas for more than or equal to 0% smaller or equal to 10%, carry out more than or equal to 10 minutes heat treatment, the concavo-convex of the upper surface 10a of GaN substrate 10 can be reduced to smaller or equal to 1nm.Picture the present invention, at edge＜1-100〉the upper surface 10a that tilted more than or equal to 0.1 ° GaN substrate 10 of direction goes up under the situation that forms the nitride-based semiconductor layer, when having on the upper surface 10a at GaN substrate 10, just can not bring into play the effect that improves flatness and improve crystalline quality to greatest extent more than or equal to 2nm concavo-convex.Therefore, in order to make effect maximum limit of the present invention ground, performance positively, before the nitride-based semiconductor layer growth, making concavo-convex being reduced to smaller or equal to 1nm of the upper surface 10a of GaN substrate 10 by heat treatment is very important.
In addition, when the heat treatment carried out for a long time GaN substrate 10, promote the decomposition of the gallium nitride in GaN substrate 10, nitrogen breaks away from from this GaN substrate 10, and consequently, the flatness of the upper surface 10a of GaN substrate 10 does not have raising.As can be seen from Figure 8, when heat treatment time surpassed 30 minutes, the concavo-convex rapid change of the upper surface 10a of GaN substrate 10 was big.Therefore, for the flatness that makes GaN substrate 10 improves reliably, heat treatment time was more satisfactory smaller or equal to 30 minutes.
In addition, about heat treatment temperature, so long as more than or equal to 800 ℃ smaller or equal to 1200 ℃, just produce same effect, the concavo-convex minimizing of the upper surface 10a of GaN substrate 10.And, by heat treatment temperature is set in more than or equal to 1000 ℃ smaller or equal to 1200 ℃, the concavo-convex further minimizing of the upper surface 10a of GaN substrate 10.Fig. 9 is illustrated in to contain NH
3Gas, N
2Gas and H
2Gas and H
2The dividing potential drop of gas is set in 20% the mixed-gas environment, when in growth furnace, GaN substrate 10 being carried out 5 minutes heat treatment, at the figure of the relation of the highest elevation difference of the upper surface 10a of GaN substrate 10 and heat treatment temperature.As shown in Figure 9, heat treatment temperature be smaller or equal to 700 ℃ situation under, a large amount of migrations at the Ga atom of the upper surface 10a of GaN substrate 10 take place hardly, so can't see concavo-convex reduction at this upper surface 10a, but, when heat treatment temperature when spending more than or equal to 800, reduce largely at the concavo-convex of this upper surface 10a.And, when heat treatment temperature is during more than or equal to 1000 ℃, further diminish in the highest elevation difference of the upper surface 10a of GaN substrate 10.On the other hand, when heat treatment temperature being set than 1200 ℃ also high, the load of the substrate heater in the MOCVD device significantly being increased, need change heater continually, is undesirable.And then nitrogen-atoms increases in the exponential function mode with respect to heating-up temperature from the probability of evaporation again of the upper surface 10a of GaN substrate 10, so using when heating than 1200 ℃ of also high temperature, in order to prevent the evaporation again of nitrogen-atoms, just need make the NH of necessity
3The flow of gas increases, and is therefore also undesirable from productive viewpoint.
In addition, at H
2The dividing potential drop of gas is smaller or equal under 30% the situation, in GaN substrate 10, because promote the migration of gallium (Ga) atom, so the concavo-convex minimizing of the upper surface 10a of GaN substrate 10.
At H
2The dividing potential drop of gas is more than or equal under 30% the situation, and the hot etching to substrate surface that is caused by heat treatment has stronger effect, so the concavo-convex of the upper surface 10a of GaN substrate 10 changes hardly.
As above, in step s 2, containing NH
3Gas or H
2Ratio be set in the NH that contains smaller or equal to 30%
3And H
2The environment of gas in, by to GaN substrate 10 more than or equal to 800 ℃ smaller or equal to the heat treatment of 1200 ℃ of execution more than or equal to 5 minutes, the flatness of the upper surface 10a of this GaN substrate 10 just improves.Therefore, the flatness of formed nitride-based semiconductor layer also further improves on the upper surface 10a of GaN substrate 10, thereby can utilize this nitride-based semiconductor layer to form the good semiconductor element of electrical characteristics.
In addition, by heat treatment time being set at, just can improve the flatness of GaN substrate 10 really smaller or equal to 30 minutes.
In addition, when GaN substrate 10 is heat-treated, the N that is comprised in the mist that in above-mentioned example, uses
2Gas has the function of carrier gas, this N
2Gas is not almost contributed the raising of the flatness of the upper surface 10a of this GaN substrate 10, so, N
2Gas may not necessarily need be included in the mist.
Figure 10 be the expression present embodiment n type semiconductor layer 11 impurity concentration and at the figure of the relation of the highest elevation difference of the upper surface of this n type semiconductor layer 11.As shown in figure 10, be set in more than or equal to 1 * 10 by impurity concentration n type semiconductor layer 11
16Cm
-3Smaller or equal to 1 * 10
20Cm
-3, Biao Mian highest elevation difference just diminishes thereon, and it is good that the configuration of surface of n type semiconductor layer 11 further becomes.In addition, be set in more than or equal to 1 * 10 by impurity concentration n type semiconductor layer 11
17Cm
-3Smaller or equal to 1 * 10
19Cm
-3, Biao Mian highest elevation difference is the value also littler than 10nm thereon, it is good that the configuration of surface of n type semiconductor layer 11 further becomes.And, be set in more than or equal to 1 * 10 by impurity concentration with n type semiconductor layer 11
17Cm
-3Smaller or equal to 5 * 10
18Cm
-3, Biao Mian highest elevation difference is littler value thereon, it is good that the configuration of surface of n type semiconductor layer 11 further becomes.
The present invention is not only applicable to other the semiconductor light-emitting elements beyond the semiconductor laser, can also be used in other electronic device.
As mentioned above, according to the present invention, can on the GaN substrate, form flatness and the superior nitride-based semiconductor layer of crystallinity.Here said crystallinity be meant result from crystallization atomic arrangement systematicness, be the electrooptics characteristic of this crystallization of the tactical rule of crystallization.When the tactical rule that can not guarantee at the nitride-based semiconductor layer, form the anomaly sxtructure of the flatness that does not rely on the GaN substrate at the nitride-based semiconductor layer.Anomaly sxtructure mainly can roughly be divided at the irregular concavo-convex of the surface of nitride-based semiconductor layer and be called as surface configuration hillock, that approved the symmetric systematicness of crystallography of reaction substrate, it has been generally acknowledged that hillock is a kind of of facet (facet) in itself.Irregular concavo-convex in the process of crystalline growth, form because the surface migration of III family atom is insufficient.When surface migration was insufficient, the probability that this III family atom is located at the place that should dispose III family atom on the crystallography originally reduced.Therefore, the characteristic degradation of the microstructure of atom level regulation.Specifically, according to the lattice defect of atom between atomic vacancy and lattice etc.,, reduce by the carrier mobility of the diffusion probability regulation of charge carrier as electrical characteristics.In addition, the result who forms the luminescence center that is caused by impurity is deterioration in optical properties.On the other hand, faceted formation causes the microscopic anisotropy of the surface migration of III family atom.Therefore, the thickness of the multiple quantum trap active layer of noise spectra of semiconductor lasers causes the fluctuation on the space.Even this fluctuation nanoscale also gives emission wavelength with great influence.
Therefore, realize that the crystalline growth that does not make anomaly sxtructure be formed on the nitride-based semiconductor layer is important obtaining aspect the good semiconductor laser characteristic in itself.In order to prevent the formation of anomaly sxtructure, as in the present invention, in advance the GaN substrate is provided with suitable deviation angle, it is effective that the growth of so-called step stream is produced.Particularly the GaN substrate 10 shown in the image pattern 1 only is provided with deviation angle in a direction, produces by making the growth of unidirectional step stream, can suppress the formation of anomaly sxtructure reliably.Because the so dynamic physical chemical phenomenon of crystalline growth is extremely complicated, so the deviation angle of predicted ideal is very difficult in theory quantitatively.It has been generally acknowledged that as present embodiment it is the higher gimmick of actuality that gimmick is by experiment investigated suitable deviation angle.
Claims (7)
1. semiconductor element, it has:
The gallium nitride substrate; And
On the upper surface of above-mentioned gallium nitride substrate, be formed in contact with this gallium nitride substrate, impurity concentration is for more than or equal to 1 * 10
16Cm
-3Smaller or equal to 1 * 10
20Cm
-3The nitride-based semiconductor layer of n type,
The above-mentioned upper surface of above-mentioned gallium nitride substrate with respect to (0001) face at＜1-100 direction has more than or equal to 0.1 ° of deviation angle smaller or equal to 1.0 °.
2. semiconductor element as claimed in claim 1, wherein,
Above-mentioned deviation angle is smaller or equal to 1.0 ° more than or equal to 0.25 °.
3. semiconductor element as claimed in claim 2, wherein,
Above-mentioned deviation angle is smaller or equal to 1.0 ° more than or equal to 0.3 °.
4. semiconductor element as claimed in claim 2, wherein,
The above-mentioned upper surface of above-mentioned gallium nitride substrate with respect to (0001) face at＜11-20 direction has more than or equal to 0 ° of deviation angle smaller or equal to 0.1 °.
5. semiconductor element as claimed in claim 1, wherein,
The impurity concentration of above-mentioned nitride-based semiconductor layer is more than or equal to 1 * 10
17Cm
-3Smaller or equal to 1 * 10
19Cm
-3
6. semiconductor element as claimed in claim 5, wherein,
The impurity concentration of above-mentioned nitride-based semiconductor layer is more than or equal to 1 * 10
17Cm
-3Smaller or equal to 5 * 10
18Cm
-3
7. the manufacture method of a semiconductor element, it has following operation:
Operation (a), prepare upper surface with respect to (0001) face at＜1-100 direction has more than or equal to 0.1 ° of gallium nitride substrate smaller or equal to 1.0 ° deviation angle; And
Operation (b), being formed in contact impurity concentration with this gallium nitride substrate on the above-mentioned upper surface of above-mentioned gallium nitride substrate is more than or equal to 1 * 10
16Cm
-3Smaller or equal to 1 * 10
20Cm
-3The nitride-based semiconductor layer of n type.
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| US9236530B2 (en) | 2011-04-01 | 2016-01-12 | Soraa, Inc. | Miscut bulk substrates |
| US9646827B1 (en) | 2011-08-23 | 2017-05-09 | Soraa, Inc. | Method for smoothing surface of a substrate containing gallium and nitrogen |
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