JPH10126008A - Semiconductor electrode material, method of forming the same, and device using the same - Google Patents

Abstract

(57) [Problem] To provide an electrode material capable of obtaining ohmic contact with a p-type II-VI compound semiconductor. SOLUTION: In a p-electrode of a II-VI group semiconductor composed of a metal 1 / contact layer 2 / p-type II-VI group semiconductor 3, a contact layer 2 is composed of an organic compound having an ionization potential of 4 eV or more and a work function of 4 eV or more. A group II-VI compound semiconductor electrode, which is a layer formed from a hybrid of metals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a p-electrode material of a II-VI compound semiconductor, a method of forming the same, and an element using the same, and more particularly to a p-electrode material used for a blue laser diode or a blue light emitting diode. A contact layer between a semiconductor material of a group VI compound semiconductor and a metal;

[0002]

2. Description of the Related Art Materials required for forming a p-electrode for a blue light emitting laser element include II-type materials such as p-type ZnSe.
Ohmic contact with group VI compound semiconductor (contact resistance is 10 ^-3
Ω · cm ² or less, more preferably 10 ⁻⁴ Ω · cm ² or less)
Specifically, the work function φ is p−
The same or as close as possible to ZnSe (φ = 6.5 eV), the resistivity ρ is small, preferably ρ <10Ω · cm
(The voltage drop at the electrode portion is 0.1 V or less), the heat resistance must be higher than 150 ° C. for Au wire bonding, and the adhesion to the insulating film and the Au wire is good. For example, it does not increase dislocations in the epi layer as deterioration resistance.

Conventionally, there are the following documents concerning electrode materials of II-VI compound semiconductors such as p-ZnSe semiconductors and methods of forming the same.

(1) US Patent No. 5274269 (Hasse et.
al., Application No. 700606, 1991) uses Au as a p-ZnSe electrode, and has a large contact barrier.
Pulse oscillation of laser (wavelength 490 nm) at K, voltage 20
V or more. (2) Ohkawa et al., (Japanese Journal of Applied
Physics, vol. 30, No. 12B, P3873, 1991), p-Z
A blue EL device using Pt as an nSe electrode and having a large contact barrier and a Schottky junction is shown. (3) Fan et al., (Appl. Phys. Lett., Vol.61 No.2
6, P3160, December 1992), Au / p-ZnSe
/ P-Zn (Se, Te) graded layer / p-Zn
In the configuration of Se, an ohmic contact is obtained. (4) Hiei et al., (Electronics Lett., 29 (10), P87
8, 1993), Au / Pt / Pd / p-ZnTe / p
The figure shows a configuration of -ZnSe, ZnTe multiple quantum well layer / p-ZnSe, which obtains ohmic contact. (5) Yoshii et al., (International Symposium on B
lue Laser and Light Emitting Diodes Chiba Univ., J
apan, 1996), Au-Ag / Ni / Te / p-Zn
P-ZnSe with Se structure and HCl surface treatment
Above, a manufacturing method in which a deposition and a heat treatment are performed, and a Schottky junction is shown. (6) JP-T 8-506694 discloses a compound semiconductor contact layer having a composition gradient containing ZnTe. (7) JP-A-6-5920 discloses metal / p-ZnTe /
p-ZnSe, metal / p-ZnTe / p-ZnSeTe
Mixed crystal / p-ZnSe, metal / p-ZnTe / p-ZnT
e quantum well layer and ZnSe barrier layer MQW / p-ZnSe
, And is an application including document (4). (8) JP-A-8-148762 discloses that an amorphous II-VI semiconductor is interposed between a II-VI semiconductor and a metal;
The structure of Au / amorphous p-ZnCdSe / p-ZnSe is shown.

[0005]

SUMMARY OF THE INVENTION Among the above documents,
In (1) and (2), there is a problem that an ohmic contact cannot be obtained, a contact resistance is large, and an operating voltage is high. This is because the doping concentration of p-ZnSe is limited,
P-Zn in which a carrier concentration of 10 ¹⁸ cm ^-3 or more cannot be obtained
This is because the work function of Se is as large as 6 eV, so that the gap between the metal work functions Au (5.1 eV) and Pt (5.6 eV) is large, and the Schottky barrier is large.

[0006] References (3), (4), (6),
In (7) and (8), ohmic contact and the one close to it are obtained. However, (3), (4) and (7) show instability due to lattice mismatch of graded or quantum well structure, There is a problem that the life is short, the film formation time is long, and the productivity is poor. This is because the difference in the lattice constant between ZnSe and ZnTe causes the introduction of defects such as dislocations, further propagates defects in the active layer and shortens the device life, and the critical film thickness due to the difference in lattice constants. The reason for this is that the growth operation is complicated and the speed is slow because of the epi growth described below.

In the literature (8) as a manufacturing method, although productivity is improved, it is amorphous and has poor resistivity and thermal conductivity. This is due to the fact that the film is amorphous rather than epi, has a high growth rate, but has low resistivity and thermal conductivity.

Document (5) is vapor deposition and heat treatment and has good productivity, but has a problem that ohmic contact cannot be obtained. This is because it is a metal multilayer film, and there is a difference in work function, which becomes a Schottky barrier.

The present invention solves the above-mentioned problems, and has a low contact resistance in a p-type II-VI electrode in a semiconductor element electrode.
An object of the present invention is to provide an electrode material capable of obtaining ohmic contact with a group III compound semiconductor and a method for forming the electrode with excellent productivity.

[0010]

In order to solve the above problems, the present invention provides a p-electrode of a metal / contact layer / p-type II-VI semiconductor comprising a p-type II-VI semiconductor, wherein the contact layer has an ionization potential. Is a layer formed from a hybrid of an organic compound having a work function of 4 eV or more and a metal having a work function of 4 eV or more.

In a p-electrode of a II-VI group semiconductor composed of a metal / contact layer / p-type II-VI group semiconductor, an organic compound having an ionization potential of 4 eV or more is used as an organic compound used for the contact layer, thereby obtaining a p-type II group. -A valence band energy gap difference from the VI semiconductor can be reduced.

Similarly, by using a metal having a work function of 4 eV or more as the metal used for the contact layer, the contact barrier between the organic compound and the metal electrode can be reduced, and the resistivity can be reduced.

Furthermore, by using a hybrid contact layer of an organic compound and a metal, a metal electrode and a p-type II-
The Schottky barrier of VI semiconductor can be substantially eliminated, and ohmic contact can be realized.

When the hybrid layer of the organic compound and the metal is a binary co-evaporated film of the organic compound and the metal, the organic compound and the metal can be formed by controlling the evaporation rate from another evaporation source. The desired contact layer can be obtained by controlling the aggregation state of the / metal hybrid film. Further, the composition can be graded by gradually changing the composition ratio between the organic compound and the metal.

A hybrid layer of an organic compound and a metal is an alternately deposited film of an organic compound and a metal, each film having a thickness of a single molecule or an atomic layer, up to 20 layers or a thickness of 10 nm or less. By alternately laminating the layers, the valence band energy gap between the p-type II-VI semiconductor and the metal electrode can be leveled, and by gradually changing the thickness of the laminated film, the organic metal The thickness of each layer may be inclined.

The organic compound used in the present invention includes phthalocyanine and metal phthalocyanine (metals: Zn, C
u, Ni, Pb, Mg, Al, In, Mn, Fe, Co
Etc.). Metal phthalocyanine is characterized in that it has a high ionization potential, low resistivity, and good heat resistance.

Further, the organic compound may be a triphenylamine derivative or a starburst amine. Triphenylamine derivatives or starburst amines are characterized by high ionization potential and high hole mobility.

Further, the organic compound may be carbon, graphite, fullerenes, or those doped with these. Carbon, graphite, fullerenes, and those doped with them are characterized by high ionization potential, low resistivity, and good heat resistance.

The organic compound may be a p-type doped conductive polymer such as polyphenylenevinylene and polyparaphenylene. The p-type doped conductive polymer has a high ionization potential and a relatively low resistivity.
There is a feature.

In the above-described method for forming an electrode of a semiconductor device, an element layer containing a p-type II-VI semiconductor is formed on a semiconductor substrate by an M method.
After being formed by the BE or MOCVD method, it is taken out of the apparatus, subjected to a surface treatment of a p-type II-VI semiconductor, introduced into a vapor deposition apparatus, and continuously vacuum-deposited without taking out a contact layer and a metal electrode layer from a vacuum. There is a way to do that.

Since the surface of the II-VI group semiconductor is easily oxidized and it is not easy to form an ohmic contact, the element layer containing the p-type II-VI semiconductor is formed on the semiconductor substrate by MBE or MOCVD as described above. Take out of the device, p-type
Perform surface treatment of II-VI semiconductors and introduce them to evaporation equipment.
The contact layer and metal electrode layer are continuously vacuum-deposited without being taken out of vacuum, so that oxidation and contamination layers are removed by surface treatment, and a contact layer is deposited on a clean surface. Electrodes can be formed without being affected by oxidation due to the above.

Further, in addition to the above method, heat treatment may be performed in an inert atmosphere or a reducing atmosphere.
By doing so, the barrier at the interface between the contact layer and the p-type semiconductor layer and the electrode layer can be further reduced by reduction or heat treatment in an inert atmosphere. For reducing atmosphere, hydrogen plasma treatment or atomic hydrogen treatment can be used.

The energy difference (gap) between the highest energy level of the valence band (valence band) of the p-type II-VI semiconductor and the Fermi level (or work function) of the electrode or contact layer is defined as a valence band energy gap. It is used for estimating the barrier height of the junction. In the prior art, the barrier height is Au (1.6 eV), Pt (1.5 eV).
V), p-ZnTe (0.5-0.8 eV), Au-A
g / Ni / Te (0.4 eV).
No ohmic contact was obtained except for (4). However, in the present invention, the work function (5.5 e
V), an organic compound having an ionization potential of 4 eV or more, more preferably an ionization potential of 5 eV
By using an organic compound having a voltage of V or more and 6.8 eV or less, a device having an electrode junction having a barrier height of 0.5 eV or less, which is smaller than the conventional one, and most preferably having no barrier can be obtained.

If the hybrid layer of the organic compound and the metal is a binary co-evaporated film of the organic compound and the metal, the composition ratio of the organic compound and the metal is changed from the p-type semiconductor layer to the metal electrode layer by the binary co-evaporation. Can be changed gradually, the work function in the hybrid layer can be graded,
Ohmic contact with metal becomes possible. Conventionally, there is an example of a p-type semiconductor mixed crystal (such as p-ZnTeSe). Compared with a semiconductor mixed crystal, the present application enables a contact layer having an excellent work function and resistivity.

The hybrid layer of an organic compound and a metal is an alternately deposited film of an organic compound and a metal, each having a thickness of a monomolecular or atomic layer, or at most 20 layers or a thickness of 1 layer.
A film having a thickness of 0 nm or less may be alternately stacked. Similarly, by gradually changing the film thickness, the work function can be inclined.
A contact layer with a small barrier and a small resistance is possible.

According to the electrode forming method of the present invention, an element layer containing a p-type II-VI semiconductor is formed on a semiconductor substrate by MBE or MO.
After being formed by the CVD method, it is taken out of the apparatus and p-type II-VI
Performs semiconductor surface treatment, introduces it into a vapor deposition device, continuously vacuum-deposits the contact layer and metal electrode layer without taking them out of the vacuum, and performs heat treatment in an inert atmosphere or a reducing atmosphere. It is possible to obtain a practical electrode and element having excellent property and low contact resistance.

[0027]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Example 1> As shown in FIG.
P-type ZnS composed of contact layer 2 / p-type ZnSe layer 3
In the p electrode of e, metal 1 was Au, contact layer 2 was a hybrid layer of an organic compound and a metal, and was a co-evaporated film.

In addition, as shown in FIG. 2A, the contact layer 2 is a co-deposited film 4 having a uniform hybrid composition as shown in FIG. 2A, and has a gradient composition of an organic compound and a metal as shown in FIG. 2B. A co-evaporated film 5 was prepared.

The following were used as the metal and the organic compound in the contact layer 2. Metals: metals and alloys such as Au, Ag, Pt, Pd, Ti and Ni, which have a work function of 4 eV or more. Organic compounds: those having an ionization potential of 4 eV or more. For example, phthalocyanine, metal phthalocyanine (metal: Zn, Cu, Ni, Pb, Mg, Al, Pt,
Be, etc.), triphenylamine derivatives, starburst amines, carbon, fullerenes, p-type doped fullerenes (such as B-doped C60), polyphenylenevinylene, polymers such as polyparaphenylene, and acceptors for these polymers. For example, a doped p-type conductive polymer.

For reference, Table 1 shows the ionization potential (eV) of each organic compound, and Table 2 shows the work functions (eV) of metals and semiconductors.

[0032]

[Table 1]

[0033]

[Table 2]

<Embodiment 2> As shown in FIG.
P-type ZnS composed of contact layer 2 / p-type ZnSe layer 3
In the p electrode of e, the metal 1 is Au, the contact layer 2 is an alternately deposited film of an organic compound deposited film 6 and a metal deposited film 7, and the thickness of each deposited film is a single molecule or a single molecule. Atomic layer, or at most 20 layers or 10n thickness
m or less were alternately laminated.

It is to be noted that, as shown in FIG. 4A, the film thickness of the organic compound vapor-deposited film 6 and the metal vapor-deposited film 7 are made constant in the contact layer 2 as a whole, and FIG. ), The thickness ratio of the organic compound deposited film 6 and the metal deposited film 7 was inclined.

Example 3 After an element layer containing a p-type II-VI semiconductor was formed on a semiconductor substrate by an MBE apparatus, the element layer was taken out into the air and subjected to a surface treatment of the p-type II-VI semiconductor surface. The semiconductor layer was obtained by introducing the contact layer and the metal electrode layer into a vapor deposition apparatus without removing the contact layer and the metal electrode layer from the vacuum.

Example 4 In addition to the method of Example 3, a heat treatment was performed in an inert atmosphere or a reducing atmosphere to obtain a semiconductor device. The conditions were as follows. Heat treatment temperature: 150 ° C to 300 ° C Heat treatment time: 5 minutes to 1 hour Atmosphere: In nitrogen gas, argon gas, hydrogen or mixed gas, or in vacuum

Example 5 A semiconductor element was obtained by an organic compound evaporation method using a resistance heating method, a sputtering method, a class ion evaporation method, an ion assisted evaporation method, and a laser evaporation method.

Example 6 A semiconductor device in which the surface treatment of a p-type semiconductor was a chemical surface treatment or a physical surface treatment was obtained. The former was performed by an acid treatment or the like, and the latter was performed by a hydrogen gas, plasma treatment or the like.

[0040]

As described above, in the p-electrode of the II-VI group semiconductor composed of metal / contact layer / p-type II-VI group semiconductor, the contact layer has an ionization potential of 4e.
By providing a group II-VI compound semiconductor device comprising a layer formed from a hybrid of an organic compound having a work function of V or higher and a metal having a work function of 4 eV or higher, the barrier height is 0.5 eV or less, which is smaller than the conventional one, most preferably A semiconductor element having no electrode junction can be obtained.

In addition, the contact layer can be formed by controlling the aggregation state of the organic / metal hybrid film by using a binary simultaneous vapor deposition method to obtain a desired contact layer.
Since the composition ratio of the organic compound and the metal can be gradually changed as the composition changes from the p-type semiconductor layer to the metal electrode layer, the present invention is more effective than a conventional p-type semiconductor mixed crystal (such as p-ZnTeSe). A contact layer having excellent work function and resistivity can be formed.

Further, if the contact layer is formed by laminating alternately deposited organic and metal films, a contact layer having a smaller barrier and lower resistance can be obtained as compared with the conventional alternate lamination of p-type semiconductors. By gradually changing the film thickness of the laminated film, the film thickness of each organic metal layer can also be inclined.

Further, according to the method for forming a semiconductor electrode of the present invention, it is possible to obtain a device having a practical electrode having excellent productivity and low contact resistance.

Further, like the superlattice contact layer, ZnS
Due to the difference between the e and ZnTe lattice constants, defects such as dislocations increase due to Joule heat during driving of the device, and a long-life device can be provided without transmitting the defects to the active layer. .

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view showing a p-type semiconductor electrode having a contact layer composed of a hybrid layer of a binary co-evaporated film of an organic compound and a metal.

FIG. 2 is an enlarged view of the contact layer of FIG. 1, in which (a) is a co-deposited film having a uniform hybrid composition;
(B) has a gradient composition of an organic compound and a metal.

FIG. 3 is an enlarged sectional view showing a p-type semiconductor electrode having a contact layer formed by laminating alternately deposited organic compound and metal films.

4A and 4B are enlarged views of the contact layer of FIG. 3, in which FIG. 4A shows a case where the thicknesses of an organic compound vapor deposition film and a metal vapor deposition film are made constant, and FIG. The film thickness ratio of the film and the metal vapor deposition film is inclined.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal 2 Contact layer 3 p-type ZnSe layer 4 Co-evaporation film of uniform composition 5 Co-evaporation film of gradient composition 6 Evaporation film of organic compound 7 Evaporation film of metal

Claims (10)

[Claims] In a p-electrode of a group II-VI semiconductor comprising a metal / contact layer / p-type group II-VI semiconductor, the contact layer is a hybrid of an organic compound having an ionization potential of 4 eV or more and a metal having a work function of 4 eV or more. An electrode material for a II-VI compound semiconductor, which is a layer formed from: 2. The electrode material for a semiconductor according to claim 1, wherein the hybrid layer of the organic compound and the metal is a binary co-evaporated film of the organic compound and the metal. 3. The above-mentioned hybrid layer of an organic compound and a metal is an alternately deposited film of an organic compound and a metal, each of which has a monomolecular or atomic layer thickness, a thickness of at most 20 layers or a thickness of 10 nm or less. 2. The semiconductor electrode material according to claim 1, wherein the electrode material is a film in which certain materials are alternately laminated. 4. An organic compound comprising phthalocyanine or metal phthalocyanine (metal: Zn, Cu, Ni, Pb, Mg, A
4. The electrode material for a semiconductor according to claim 1, wherein the material is l, In, Mn, Fe, Co, or the like. 5. The semiconductor device according to claim 1, wherein the organic compound is a triphenylamine derivative or a starburst amine. 6. An organic compound comprising carbon, graphite,
4. The electrode material for a semiconductor according to claim 1, wherein the material is a fullerene or a doped material thereof. 7. The organic compound is polyphenylene vinylene,
4. The electrode material for a semiconductor according to claim 1, which is a p-type doped conductive polymer such as polyparaphenylene. 8. An element layer containing a p-type II-VI semiconductor is formed on a semiconductor substrate by MBE or MOCVD, and then taken out of the device and subjected to a surface treatment of the p-type II-VI semiconductor.
A method for forming a semiconductor electrode, comprising: introducing a contact layer and a metal electrode layer into a vapor deposition apparatus; 9. The method for forming a semiconductor electrode according to claim 8, wherein the heat treatment is performed in an inert atmosphere or a reducing atmosphere in addition to the method of claim 8. 10. A semiconductor device using the electrode material according to claim 1.