JP5898347B2 - Method for manufacturing light emitting device - Google Patents

Description

  The present invention relates to a method for manufacturing a light emitting element having an emission wavelength in the ultraviolet region.

  A group III nitride semiconductor is suitable as a constituent material of a light-emitting element having a light emission wavelength in a short wavelength region (blue to purple to ultraviolet) because it has a wide band gap and a transition between bands is a direct transition type.

As an example of such a light-emitting element, the carrier concentration is controlled by adding Si dopant to the n-type layer made of group III nitride in a concentration range of 3 × 10 ¹⁷ cm ⁻³ or more and 5 × 10 ¹⁹ cm ⁻³ or less. In addition, a light-emitting diode and a semiconductor laser in which high crystal quality and sufficient mobility are realized in the n-type layer and the emission wavelength is 200 nm in the ultraviolet region are already known (for example, see Patent Document 1). ).

JP 2003-273398 A

  A so-called PN-type semiconductor light emitting device having a light emission wavelength in the ultraviolet region is realized by using Al-rich AlGaN. In order to increase the luminous efficiency, it is important to reduce the resistance of the n-type layer while maintaining high crystal quality. This is because the resistivity of the n-type layer is inversely proportional to the product of the carrier concentration and the mobility, so that the resistivity is reduced or reduced in the n-type layer formed using Al-rich AlGaN. This is because at least an increase in carrier concentration or an increase in mobility occurs. Both the increase in carrier concentration and the increase in mobility contribute to improvement in luminous efficiency.

  In Patent Document 1, there is a description that an n-type layer has a high resistance when Al is rich, but there is no specific disclosure about a technique for realizing a low resistance of the n-type layer in such a case. Absent.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a light-emitting element having a light emission wavelength in the ultraviolet region and having a high light emission efficiency.

In order to solve the above-described problems, the invention of claim 1 is a method for manufacturing a light emitting device, wherein an n-type layer forming step of epitaxially forming an n-type layer made of a first group III nitride on a predetermined substrate is performed. A light emitting layer forming step of epitaxially forming a light emitting layer made of a second group III nitride on the n type layer, and a p type layer made of a third group III nitride on the light emitting layer A p-type layer forming step of forming an epitaxial layer, wherein the first group III nitride has a composition range of Al _x Ga _1-x N (0 ≦ x ≦ 1), and the second group III nitride is Al _y Ga _1-y N (0 ≦ y ≦ 1) in a composition range having an emission wavelength in the ultraviolet region, and the n-type layer forming step in the formation temperature of 1150 ° C. or higher 1200 ° C. or less, formation pressure Specific resistance for forming the n-type layer below 1.5Ωcm With 10Torr least 50Torr or less, and wherein the.

According to a second aspect of the invention a method of manufacturing a light emitting device according to claim 1, wherein the substrate comprises a substrate made of single crystal sapphire, formed by epitaxially formed on the substrate, Al _p Ga _{1 -P} N (0.8 ≦ p ≦ 1), and in the n-type layer forming step, the n molar concentration is lower on the growth base layer than in the growth base layer. A mold layer is formed.

The invention according to claim 3 is a method for manufacturing a light emitting device, wherein a growth base layer made of Al _p Ga _1-p N (0.8 ≦ p ≦ 1) is epitaxially formed on a base material made of single crystal sapphire. A heat treatment step of heating the substrate formed to at least 1250 ° C. or more, and an n-type layer formation on the substrate by epitaxially forming a first group III nitride having an Al molar concentration lower than that of the growth base layer A light emitting layer forming step of epitaxially forming a light emitting layer made of a second group III nitride on the n-type layer; and a p-type made of a third group III nitride on the light emitting layer. A p-type layer forming step of forming a layer epitaxially, wherein the first group III nitride has a composition range of Al _x Ga _1-x N ( 0 ≦ x ≦ 1), and the second III Nitride is _Al y _{Ga 1-y} N in the composition range having an emission wavelength in the ultraviolet region (0 ≦ y ≦ 1), in the n-type layer forming step, a forming temperature of 1150 ° C. or higher 1200 ° C. or less In addition, the n-type layer having a specific resistance of 1.5 Ωcm or less is formed by setting the forming pressure to 10 Torr or more and 50 Torr or less .

According to the first to third aspects of the present invention, it is possible to realize a light emitting device having a light emitting wavelength in the ultraviolet region, which is excellent in light emission efficiency and has a low resistance and high crystal quality in the n-type layer. it can.

1 is a diagram schematically showing a cross-sectional structure of a light emitting element 10. FIG. It is a figure which shows the relationship between the growth temperature of the n-type layer 2, and a specific resistance. It is a figure which shows the relationship between the growth temperature of n-type layer 2, and carrier concentration. It is a figure which shows the relationship between the growth pressure of the n-type layer 2, and a specific resistance. It is a figure which shows the relationship between the growth pressure of n-type layer 2, and carrier concentration. It is a figure which shows the relationship between the impurity concentration ratio of the n-type layer 2, and growth temperature. It is a figure which shows the relationship between the impurity concentration ratio of the n-type layer 2, and growth pressure. It is a figure which shows the relationship between the activation rate of Si atom, and total impurity concentration ratio.

<Configuration outline of light emitting element>
FIG. 1 is a diagram schematically showing an example of a cross-sectional structure of a light-emitting element 10 according to an embodiment of the present invention. The light-emitting element 10 is a laminated structure in which an n-type layer 2, a light-emitting layer 3, and a p-type layer 4 are epitaxially formed in this order on a substrate 1. Here, the substrate 1 is a so-called epitaxial substrate (or also referred to as a template substrate) composed of a base material 1a and a growth base layer 1b formed epitaxially thereon. In the light emitting element 10, the p-type electrode 5 is formed on the p-type layer 4 with Au / Ni or the like. Further, an n-type electrode 6 such as Al / Ti is formed on the n-type layer 2 exposed by removing a part of the light emitting layer 3 and the p-type layer 4 by etching or the like. For the convenience of illustration, the ratio of the thickness of each layer and the ratio of length to width in the drawing of FIG. 1 do not reflect the actual ratio.

  The light emitting element 10 is a so-called PN type semiconductor light emitting element. Light of a predetermined wavelength is emitted by confining carriers in the light emitting layer 3 by applying a voltage between the p-type electrode 5 and the n-type electrode 6 and recombination thereof. The emission wavelength is determined by the composition of the light emitting layer 3 and the like. The light emitting element 10 according to the present embodiment is configured to have an emission wavelength in the ultraviolet region.

Regardless of the presence or absence of the growth base layer 1b formed thereon, the substrate 1a is appropriately selected according to the forming method of each layer including the layer formed thereon. For example, a substrate such as SiC (silicon carbide) or sapphire is used. Alternatively, various oxide materials such as ZnO, LiAlO ₂ , LiGaO ₂ , MgAl ₂ O ₄ , (LaSr) (AlTa) O ₃ , NdGaO ₃ , MgO, various IV group single crystals such as Si, Ge, and C, and various IV such as SiGe Various III-V compounds such as -IV group compounds, GaAs, AlN, GaN and AlGaN, and various borides such as ZrB ₂ may be appropriately selected and used.

  However, since the substrate 1a has an emission wavelength in the ultraviolet region, it is desirable to use a material that is transparent to light having a wavelength in the region. Considering the compatibility with the crystal structure of the group III nitride constituting the growth base layer 1b described below, sapphire is most preferable as the substrate 1a. When obtaining a group III nitride crystal having a (0001) plane as a main surface as the growth underlayer 1b, for example, (11-20) plane and (0001) plane sapphire can be used as the substrate 1a. Further, when a group III nitride crystal having a (11-20) plane as a main surface is obtained as the growth underlayer 1b, for example, (10-12) plane sapphire can be used as the substrate 1a. The thickness of the substrate 1a is not particularly limited in terms of material, but a thickness of several hundreds μm to several mm is preferable for convenience of handling.

The growth underlayer 1b is an epitaxial film made of a group III nitride crystal formed by a known film formation method such as MOCVD, MBE, or HVPE. The group III nitride crystal here is, for example, Al _p Ga _1-p N (0 <p ≦ 1). Al _p Ga _1-p N (0.8 ≦ p ≦ 1) is preferable. More preferred is AlN. Here, since AlN can be formed with a single composition, there is no problem of composition distribution or the like, and it is the most preferable form. However, by setting Al _p Ga _1-p N (0.8 ≦ p ≦ 1), AlN The physical properties are similar to each other, and there are almost the same effects in terms of crystal quality and physical properties. Note that the MOCVD method can be combined with a PALE method (pulsed atomic layer epitaxy), a plasma assist method, a laser assist method, or the like. Similar techniques can be used in combination with the MBE method and the HVPE method. Growth methods such as MOCVD, MBE, and HVPE are suitable for growing high-quality crystals because the manufacturing conditions can be controlled with high precision. The same applies to the subsequent formation of each layer with respect to these growth methods.

  The growth underlayer 1b is a suitable example formed to a thickness of about several hundred nm to several μm. As for the surface form of the underlayer 1b, for example, those having a concavo-convex shape processed to promote ELO growth, those having a texture structure when the underlayer 1b is formed, those having a flat surface at the atomic level, etc. As a preferred example, the substrate 1 having the growth base layer 1b having an outermost surface roughness of 0.3 nm or less can be obtained by appropriately determining the manufacturing conditions. That is, the substrate 1 in which the atomic level flatness is realized is obtained. In the present application, the arithmetic average roughness Ra in a 5 μm × 5 μm square region evaluated by an AFM (atomic force microscope) is defined as the surface roughness.

  When the growth base layer 1b is formed by the MOCVD method, it is preferable that the heating temperature of the substrate 1a is set in a range of 1300 ° C. to 1400 ° C., and the pressure in the reaction tube is set to 10 Torr to 50 Torr. It is an example.

The growth underlayer 1b generally contains dislocations of about 1 × 10 ¹⁰ / cm ² or more. In group III nitride crystals, two types of dislocations, screw dislocations and edge dislocations, can exist, but edge dislocations mainly exist in the growth underlayer 1b. In this embodiment, the dislocation density is evaluated by a planar TEM. Further, the half width of the (0002) plane by X-ray rocking curve measurement is 150 seconds or less, and the half width of the (10-12) plane is 1500 seconds or less.

  The thickness of the growth foundation layer 1b is not particularly limited, and an optimum film thickness is selected for the device structure or usage pattern to be finally used. For example, a film thickness of about several nm to several mm is assumed. In addition, the composition of the growth base layer 1b shows an average composition, and it is not always necessary to make the composition uniform. For example, a gradient composition or a stress relaxation layer having a different composition can be inserted. is there.

  In addition, impurities such as H, C, O, Si, B, In, and transition metals that are unavoidably included when the growth base layer 1b is formed may exist in the growth base layer 1b. In addition, impurities such as Si, Ge, Be, Mg, Zn, and Cd, which are intentionally introduced for controlling the conductivity, may be included.

The n-type layer 2 is an epitaxial film made of a group III nitride crystal formed on the substrate 1 as described above by a known film forming method such as MOCVD method or MBE method. However, the group III nitride crystal here is specifically Al _x Ga _1-x N (0 ≦ x ≦ 1) having a composition range that does not have the ability to absorb light having a wavelength of 300 nm or less. . When satisfying such requirements, ultraviolet light emitted from the light emitting layer 3 passes through the n-type layer without being absorbed, so that high light emission efficiency is realized in the light emitting element 10. It has been confirmed by the inventor of the present invention that this requirement is satisfied if at least x> 0.5. x = 0.6 is a suitable example.

The n-type layer 2 is doped with Si as an n-type dopant at a predetermined concentration. In the case where the n-type layer 2 is produced by the MOCVD method, the doping is performed by flowing a silane (SiH ₄ ) gas at a predetermined supply flow rate in addition to the supply of the source gas for forming the group III nitride. Realized. On the other hand, the n-type layer 2 inevitably contains C atoms, O atoms and other impurities.

The n-type layer 2 is a suitable example formed to a thickness of about 1 to 5 μm. By appropriately determining the production conditions, the dislocation density is 1 × 10 ¹⁰ / cm ² or less, the half width of the (0002) plane by X-ray rocking curve measurement is 300 seconds or less, and the (10-12) plane An n-type layer 2 having a good crystal quality and a half width of 1200 seconds or less can be obtained. Thereby, good crystal quality can be obtained also in the light emitting layer 3 and the p-type layer 4 formed thereon.

  The specific resistance of the n-type layer 2 varies depending on the manufacturing conditions. In the present embodiment, when the MOCVD method is used, the growth temperature is set to 1150 ° C. to 1200 ° C. and the growth pressure is set to 10 Torr to 50 Torr, thereby reducing the resistance of the n-type layer 2 and increasing the carrier concentration. It is confirmed by the inventor of the present invention that it is suitable for realizing the above. Details thereof will be described later.

The light emitting layer 3 is an epitaxial film made of a group III nitride crystal formed on the n-type layer 2 by a known film forming method such as MOCVD method or MBE method. However, the group III nitride crystal here is specifically Al _y Ga _1-y N (0 ≦ y ≦ 1) in a composition range having an emission wavelength in the ultraviolet region. For example, if y = 0.5, light emission with a wavelength of 260 nm belonging to the ultraviolet region is realized. The light emitting layer 3 is a suitable example formed to a thickness of about 5 nm to 30 nm. The light emitting layer 3 may contain In or B, and may have a multi-period quantum well structure.

The p-type layer 4 is an epitaxial film made of a group III nitride crystal formed on the light emitting layer 3 by a known film forming method such as MOCVD method or MBE method. The group III nitride crystal here is, for example, Al _z Ga _1-z N (0 ≦ z ≦ 1). An example is z = 0.6.

  The p-type layer 4 is doped with Mg, Be, Mg, Sr, Zn, Cd, etc. as a p-type dopant at a predetermined concentration. The p-type layer 4 is a suitable example formed to a thickness of about 0.1 to 0.3 μm.

  The formation of the n-type layer 2, the light-emitting layer 3, and the p-type layer 4 on the substrate 1 is a mode in which all or a part thereof is continuously performed using the same MOCVD apparatus or MBE apparatus. May be. In the case where the substrate 1 is an epitaxial substrate, the same apparatus may be used from the formation of the growth base layer 1b on the base material 1a to the formation of the p-type layer 4.

<Low resistance of n-type layer>
Next, a description will be given of suitable manufacturing conditions for realizing the low resistance of the n-type layer 2 described above. 2, FIG. 3, FIG. 4, and FIG. 5 are diagrams for explaining this. Here, a case will be described in which sapphire is used as the base material 1a, a substrate 1 formed of AlN is used as the growth base layer 1b, and the n-type layer 2 is formed under various conditions by MOCVD. As the source gas, TMA (trimethylaluminum), TMG (trimethylgallium), and NH ₃ are used, and are supplied so that the supply flow ratio for each minute is 1: 1: 4000. Further, the silane gas for Si doping is supplied so that the Si concentration in the n-type layer 2 is 1 × 10 ¹⁹ / cm ² .

  2 and 3 respectively show the relationship between the growth temperature and the specific resistance of the generated n-type layer 2 when the n-type layer 2 is formed at various growth temperatures, and the growth temperature and the n-type layer 2. It is a figure which shows the relationship with carrier concentration. The pressure at that time is 15 Torr. The specific resistance is a value obtained by an eddy current resistance measuring device. The carrier concentration is a value obtained by CV measurement using a mercury probe. Further, the growth temperature indicates the heating temperature of the substrate 1. If the MOCVD apparatus is used, the tray on which the substrate 1 is installed (for example, a carbon member with a corrosion-resistant coating (4 mm thickness)) Measured by a thermocouple in close proximity to The pressure indicates the pressure in the reaction tube of the MOCVD apparatus. The same applies to the cases of FIG. 4 and FIG.

  4 and 5 show the relationship between the growth temperature and the specific resistance of the generated n-type layer 2 when the n-type layer 2 is formed by applying various growth pressures by the MOCVD method, and the growth pressure and It is a figure which shows the relationship of the carrier concentration of the n-type layer. The temperature at that time is 1200 ° C.

  2 and 3, it is confirmed that when the growth temperature is 1150 ° C. to 1200 ° C., a high carrier concentration is obtained and a remarkable low resistance of 1.5 Ωcm or less is realized. 4 and 5, a high carrier concentration is obtained in the pressure range of 10 Torr to 50 Torr, and a low resistance state of 1.0 Ωcm or less is also realized. From these, it can be said that it is preferable to set the growth temperature to 1150 ° C. to 1200 ° C. and the growth pressure to 10 Torr to 50 Torr in order to realize low resistance of n-type layer 2 and increase of carrier concentration. In addition, as described above, good crystal quality is realized in the n-type layer 2 in the low resistance state.

  According to the results of FIGS. 2 to 5, the resistance value of the n-type layer 2 does not change monotonically with respect to the growth temperature and pressure, but changes from decreasing to increasing at certain values for both. In other words, a minimal state exists. Factors that are considered to cause such a result are shown below.

  FIG. 6 shows the ratio of the concentration of O atoms and C atoms present as impurities in the n-type layer 2 to the concentration of Si atoms present in the n-type layer 2 (referred to as impurity concentration ratio), the growth temperature, It is a figure shown about the relationship. FIG. 6 also shows the impurity concentration ratio for the total concentration of O atoms and C atoms (this may be referred to as the total impurity concentration ratio). Similarly, FIG. 7 is a diagram showing the relationship between the impurity concentration ratio and the pressure. The concentration of each atom is measured by SIMS (secondary ion mass spectrometer). For the SIMS measurement, a quadrupole SIMS apparatus manufactured by Physical Electronics was used, and measurement was performed with primary ions (cesium ions) incident at an acceleration voltage of 5 keV and an incident angle of 60 °. In addition, AlN and GaN were used as standard samples for absolute value calibration.

  Comparing the change of the impurity concentration with respect to the growth temperature in FIG. 6 and the change of the specific resistance in FIG. 2, the change in the impurity concentration ratio with respect to the temperature for each of the O atom and the C atom in FIG. Not consistent with resistance change. However, the change of the total impurity concentration ratio with respect to the growth temperature, specifically, the change that the total impurity concentration ratio decreases as the growth temperature increases until the growth temperature is 1200 ° C., but starts to increase when the growth temperature is higher than 1200 ° C. In other words, the change that the minimum exists is in good agreement with the change of the resistivity with respect to the growth temperature. The same can be said by comparing the change in the impurity concentration ratio with respect to the growth pressure in FIG. 7 with the change in the specific resistance in FIG.

  In view of these, it is determined that there is a correlation between the magnitude of the specific resistance in the n-type layer 2 and the total impurity concentration ratio of O atoms and C atoms as impurities. On the other hand, since the behavior of the change in the impurity concentration ratio with respect to the change in the growth conditions is different between the O atom and the C atom, it is possible to control the total impurity concentration ratio, rather than controlling them individually, by changing the n-type. It can be said that it is effective for lowering the resistance of the layer 2. For example, when the total impurity concentration ratio is approximately 0.8 or less, formation of the n-type layer 2 having a sufficiently small specific resistance of 1.5 Ωcm or less is realized. Specifically, as described above, when the growth temperature is 1150 ° C. to 1200 ° C. and the growth pressure is 10 Torr to 50 Torr, formation of the n-type layer 2 having such a low specific resistance is realized.

  FIG. 8 illustrates the meaning of the correlation between the total impurity concentration ratio and the specific resistance. The relationship between the activation rate of Si atoms acting as a donor in the light emitting device 10 and the total impurity concentration ratio is shown. FIG. FIG. 8 shows that a high activation rate can be obtained in a region where the total impurity concentration ratio is less than 0.8. Since the carrier concentration increases as the activation rate increases, it can be understood that the realization of the low resistance state as described above means that the carrier concentration is increased. Further, FIG. 8 shows that it is effective to increase the carrier concentration, that is, to improve the light emission efficiency, rather than trying to decrease each of O atoms and C atoms independently. It means that.

  As described above, according to the present embodiment, a light-emitting element having a light emission wavelength in the ultraviolet region and having a high light emission efficiency is realized. Specifically, a light-emitting element having an n-type layer that has low resistance, high crystal quality, and has no ability to absorb light in the ultraviolet region can be realized. In particular, for low resistance, the ratio of the sum of the concentration values of oxygen atoms and carbon atoms to the concentration value of Si atoms in the n-type layer is set to 0.8 or less so that a sufficiently small ratio of 1.5Ωcm or less Resistance is realized.

<Modification>
When the light emitting element 10 is formed using the substrate 1 composed of the base material 1a and the growth base layer 1b formed by epitaxially forming the group III nitride crystal film thereon as described above, the n-type layer 2 Prior to the formation, a heat treatment may be performed by heating the substrate 1 to at least 1250 ° C. or more, preferably 1500 ° C. or more by a predetermined processing apparatus. Thereby, the improvement of the crystal quality of the group III nitride crystal constituting the growth foundation layer 1b is realized. Such heat treatment is particularly effective for reducing dislocations in the growth base layer 1b and eliminating pits on the surface. For example, the dislocation density decreases to approximately 1/10 or less. In particular, edge dislocations can be effectively eliminated. As described in the above embodiment, the growth base layer 1b includes dislocations of about 1 × 10 ¹⁰ / cm ² or more, but prior to the formation of the n-type layer 2, heat treatment is appropriately performed. By doing so, the dislocations in the growth underlayer 1b are reduced by about one order compared to before the heat treatment. In the n-type layer 2 formed without heat treatment, a dislocation density of 1 × 10 ¹⁰ / cm ² or less is realized. However, even in the n-type layer 2 formed after the heat treatment, the heat treatment is not performed. It has been confirmed by the inventors of the present invention that the dislocation density is reduced by about one order. In addition, it has an effect of causing an inclination of the traveling direction of dislocations in the n-type layer 2 from a direction penetrating in parallel with the film thickness growth direction and promoting the disappearance of dislocation density. At the same time, it has been confirmed that the n-type layer 2 is coherently grown to the lattice constant of AlN to generate a large compressive stress.

  That is, the crystal quality of the n-type layer can be further improved by forming the n-type layer 2 after performing such heat treatment. In addition, when such heat treatment is applied, an effect of suppressing the uptake of impurities of O atoms and C atoms has been confirmed.

  The reason for setting the heating temperature to at least 1250 ° C. or higher is that the temperature of the substrate itself is generally 1250 ° C. or lower when the growth base layer 1b is formed by MOCVD or the like. This is because at least the effect of reducing dislocations can be obtained. Since a film forming method such as MOCVD is generally a method of forming a film by a non-equilibrium reaction, the formed epitaxial film has more crystal defects (dislocations, etc.) than the number existing in a thermal equilibrium state. Although it is thought that it exists in the state which was frozen, it is guessed that by heating to 1250 degreeC or more, a thermal equilibrium state will be approached and a dislocation | rearrangement will be reduced. However, this does not limit the formation temperature of the growth base layer 1b by the MOCVD method to 1250 ° C. or lower, and it may be formed at a temperature higher than that. In the case of a group III nitride mainly composed of Al, particularly AlN, it is assumed that the formation temperature by MOCVD is increased to 1250 ° C. or higher. Of course, even when the film is formed at a substrate temperature of 1250 ° C. or higher, the effect of reducing dislocation can be obtained by performing the heat treatment at a temperature higher than the substrate temperature.

  The improvement in crystal quality by such heat treatment is particularly effective when the proportion of Al in all group III elements in the group III nitride constituting the growth underlayer 1b is 80 mol% or more. This is effective in the case of AlN. When the group III nitride is AlN, there is no problem of variations such as composition fluctuations. Therefore, this case is most preferable for quality control. However, if the Al ratio in all group III elements is 80 mol% or more, the AlN In the heat treatment at the same temperature as the case, the same effect of improving the crystal quality is confirmed, and the quality of the growth foundation layer 1b before the heat treatment is almost the same as that of AlN. When the proportion of Al in all group III elements is less than 80%, if heat treatment is performed at the same temperature as in AlN, the occurrence of pits due to evaporation of other group III elements, such as Ga components, becomes a problem, and surface flatness May be damaged.

  The atmosphere during the heat treatment is preferably an atmosphere containing nitrogen element in order to prevent the decomposition of the group III nitride. For example, an atmosphere containing nitrogen gas or ammonia gas can be used. Regarding the pressure conditions during the heat treatment, it has been confirmed that the crystal quality can be improved at any pressure from reduced pressure to increased pressure.

  Note that the heat treatment is to improve the crystal quality of the growth base layer 1b formed thereon by utilizing the regularity of the crystal arrangement of the substrate 1a which is a single crystal. Therefore, the material used as the substrate 1a is preferably one that does not decompose or melt in the temperature zone of the heat treatment for improving the crystal quality, or one that does not react strongly with the group III nitride crystal forming the growth underlayer 1b. . However, it is not excluded from the present invention that an ultrathin reaction product is generated entirely or locally at the interface between the substrate 1a and the growth underlayer 1b by the heat treatment. In some cases, the presence of such an ultrathin reaction product is preferable, such as acting as a buffer layer for reducing dislocations.

  Accordingly, the heat treatment is performed in a temperature range that does not exceed the melting point of the base material 1a, or in a temperature range in which the formation of a reaction product between the base material 1a and the growth base layer 1b does not occur remarkably, that is, a growth base layer due to excessive reaction. It is desirable to carry out in a temperature range in which the crystal quality of 1b does not deteriorate. In particular, when sapphire is used as the substrate 1a and the growth underlayer 1b is formed of a group III nitride containing Al, heat treatment is performed in a temperature range in which γ-ALON is not significantly formed at the interface between the two. preferable. This is because, if γ-ALON is formed remarkably, the surface roughness of the growth underlayer 1b increases, making device application difficult.

DESCRIPTION OF SYMBOLS 1 Board | substrate 1a Base material 1b Growth base layer 2 N-type layer 3 Light emitting layer 4 P-type layer 5 P-type electrode 6 N-type electrode 10 Light emitting element

Claims (3)

A method of manufacturing a light emitting device,
An n-type layer forming step of epitaxially forming an n-type layer made of a first group III nitride on a predetermined substrate;
A light emitting layer forming step of epitaxially forming a light emitting layer made of a second group III nitride on the n-type layer;
A p-type layer forming step of epitaxially forming a p-type layer made of a third group III nitride on the light emitting layer;
With
The first group III nitride is Al _x Ga _1-x N (0 ≦ x ≦ 1) in a composition range in which the wavelength is not more than 300 nm and does not have the ability to absorb light,
The second group III nitride is Al _y Ga _1-y N (0 ≦ y ≦ 1) in a composition range having an emission wavelength in the ultraviolet region,
In the n-type layer forming step, the n-type layer having a specific resistance of 1.5 Ωcm or less is formed by setting a forming temperature to 1150 ° C. or more and 1200 ° C. or less and forming pressure to 10 Torr or more and 50 Torr or less .
A method for manufacturing a light-emitting element. It is a manufacturing method of the light emitting element according to claim 1 ,
The substrate is
A substrate made of single crystal sapphire,
A growth foundation layer made of Al _p Ga _1-p N (0.8 ≦ p ≦ 1) , which is epitaxially formed on the substrate;
Consists of
In the n-type layer forming step, the n-type layer having an Al molar concentration lower than that of the growth base layer is formed on the growth base layer.
A method for manufacturing a light-emitting element. A method of manufacturing a light emission element,
A heat treatment step of heating a substrate formed by epitaxially forming a growth base layer made of Al _p Ga _1-p N (0.8 ≦ p ≦ 1) on a base material made of single crystal sapphire to at least 1250 ° C. or more; ,
An n-type layer forming step of epitaxially forming the first group III nitride having a lower Al molar concentration than the growth base layer on the substrate;
A light emitting layer forming step of epitaxially forming a light emitting layer made of a second group III nitride on the n-type layer;
A p-type layer forming step of epitaxially forming a p-type layer made of a third group III nitride on the light emitting layer;
With
The first group III nitride is Al _x Ga _1-x N (0 ≦ x ≦ 1) in a composition range in which the wavelength is not more than 300 nm and does not have the ability to absorb light ,
The second group III nitride is Al _y Ga _1-y N (0 ≦ y ≦ 1) in a composition range having an emission wavelength in the ultraviolet region ,
In the n-type layer forming step, the n-type layer having a specific resistance of 1.5 Ωcm or less is formed by setting a forming temperature to 1150 ° C. or more and 1200 ° C. or less and forming pressure to 10 Torr or more and 50 Torr or less.
A method for manufacturing a light-emitting element.

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