JPH07321415A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a II-VI compound semiconductor device in which the resistance of a p-side electrode part is lowered and which can be operated at a low voltage and a low power consumption by a method wherein the p-side electrode part is formed in such a way that a ZnTexSe1-x layer and a ZnTe layer are laminated and that a metal electrode is constituted on them so as to come into ohmic contact. CONSTITUTION:A p-side electrode part 21 with reference to a II-VI compound semiconductor element is constituted of a ZnTexSe1-x layer 22 on the II-VI compound semiconductor element 13, of a ZnTe layer 23 on it and of a metal electrode 9 which comes into ohmic contact with the ZnTe layer 23. Holes which are injected into the ZnTe layer 23 from the metal electrode 9 are injected into the II-VI compound semiconductor element 13 via a trap level due to Te existing in the ZnTexSe1-x layer 22. That is to say, since the ZnTexSe1-x layer 22 is interposed between the semiconductor element 13 and the ZnTe layer 23, a barrier with reference to the holes becomes low and thin, and the tunneling probability of the holes is increased. Consequently, an ohmic characteristic in the p-side electrode part 21 becomes good.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device using a II-VI group compound semiconductor, for example, a II-VI group compound semiconductor light emitting device.

[0002]

2. Description of the Related Art For example, in magneto-optical recording in which recording and / or reproduction are performed by a laser beam, there is an increasing demand for using a short wavelength, for example, a blue semiconductor laser as a laser of a light source for improving recording density.
Zn _A Mg _1-A Group II-VI as the semiconductor laser of this type
S _B Se _1-B based semiconductor lasers are receiving attention.

This ZnMgSSe type II-VI group compound semiconductor laser is generally a III-V group compound semiconductor such as G.
A configuration is adopted in which each II-VI group semiconductor layer is epitaxy on a substrate such as aAs or InP. In this case, when a desired semiconductor laser is formed by epitaxy a p-type II-VI group epitaxial layer, that is, a cladding layer on a p-type substrate, a barrier against holes is generated between the substrate and the epitaxial layer. This kind of II from increasing the operating voltage
-In Group VI compound semiconductor lasers, II on the n-type substrate
A configuration is adopted in which the group VI compound semiconductor layer is formed by epitaxy.

Therefore, in the case of this structure, the p-side electrode portion in which the electrode is provided on the upper layer of the epitaxied II-VI group compound semiconductor layer, that is, on the so-called cap layer side is formed.

Also in the p-side electrode portion, it is desired that the contact resistance be as small as possible. This is because when the contact resistance in this electrode portion becomes large, there is a problem that the life of the laser is shortened by heat generation and the operating voltage is increased.

ZnMgSS of this II-VI group compound semiconductor
The e-based semiconductor laser is, for example, as shown in FIG.
An n-type ZnSe buffer layer 2, a first cladding layer 3 of n-type ZnMgSSe, a first guide layer 4 of ZnSSe, and ZnCdSe are sequentially formed on one surface of the aAs substrate 1.
An active layer 5, a second guide layer 6 of ZnSSe, a second cladding layer 7 of p-type ZnMgSSe, and in some cases an intermediate layer 8 of p-type ZnSSe having a buffer effect and a cladding effect on it. Through the p-type S
It has a II-VI group compound semiconductor element portion 13 in which a cap layer 11 made of ZnSe containing or not containing (hereinafter referred to as Zn (S) Se) is formed. And p on this
The so-called electrode contact layer formed by the ZnTe layer 12 of the p-type is epitaxy, and the p-side metal electrode 9 made of an alloy of Au, for example, an Au alloy containing Pd and Pt, for example, is ohmic-contacted on the p-type ZnTe layer 12. The p-side electrode portion 14 is configured. An electrode 10 made of, for example, In is ohmic-contacted with the other surface of the substrate 1.

Here, this type of II-VI group compound semiconductor device is used.
As described above, in the p-side electrode portion 14,
A metal electrode directly on the p-type ZnSe layer 11 of the cap layer
To form a p-type ZnTe layer 12 without depositing 9
Is Zn_AMg_1-AS_BSe _1-BIn the system, A = 1,
For the cap layer 11 made of Zn (S) Se with B ≦ 1
It is not possible to dope p-type impurities to a sufficiently high concentration.
In contrast, ohmic contact with low resistance contact
This is because there is no electrode metal material that can be used for tact.
On top of this, a metal of an Au alloy containing, for example, Pd and Pt described above.
Can make ohmic contact with the electrode 9 with sufficiently low resistance
The ZnTe layer 12 is provided.
It

In the above II-VI group compound semiconductor device, p
As the other side of the side electrode portion 14, as shown in FIG. 5, p-type ZnTe is formed on the p-type ZnSe layer 11 which is a cap layer.
A multiple quantum well (MQW) structure 18 is formed by stacking a thin layer 16 and a p-type ZnSe thin layer 17, and a p-type ZnTe layer 19 is further stacked thereon, and the p-type ZnTe layer 19 is formed. There has been proposed a structure in which the metal electrode 9 is adhered and formed.

As still another example of the p-side electrode portion 14, although not shown, after an alloy film of Te and Se or a Zn compound containing Te and Se is formed, heat treatment is performed, and a slight amount of Vb is formed thereon. A structure in which Au containing a group element is vapor-deposited is also known. Moreover, after p-type ZnSe is laminated on a semi-insulating GaAs substrate, p-type ZnTe _x Se _1-x (x> 0.5) is formed, and Au—Sb (Sb: 1%) is vapor-deposited on this. It is also known that a p-side electrode is then formed by heat treatment (see JP-A-2-122565).

[0010]

By the way, the above-mentioned p
In the side electrode portion 14, when the metal electrode 9 is formed by providing the p-type ZnTe layer 12 on the cap layer 11 made of the p-type ZnSe layer shown in FIG. 4, the p-type ZnTe layer 12 and the metal electrode 9 are formed. A good ohmic contact is formed between them, but a Schottky junction is formed between the p-type ZnTe layer 12 and the p-type ZnSe layer 11 that is the cap layer on the element part 13 side, and good ohmic characteristics are obtained. Therefore, there is a problem that the operating voltage cannot be sufficiently reduced.

As the p-side electrode portion 14, as shown in FIG. 5, the cap layer 11 made of a p-type ZnSe layer and the p-type Z are formed.
When the multiple quantum well structure 18 including the p-type ZnTe thin layer 16 and the p-type ZnSe thin layer 17 is interposed between the nTe layer 19 and the nTe layer 19, when the multiple quantum well structure 18 is manufactured, There is a problem that there are many parameters that must be controlled and it is not easy to manufacture.

Further, an alloy film of Te and Se or Te and Se is used.
When a heat treatment is performed to form a Zn compound containing Al, and Au containing a small amount of a Vb group element is vapor-deposited thereon, the heat treatment may cause deterioration of the semiconductor laser.

In the above example, the p-side electrode portion in the II-VI group compound semiconductor laser was described, but the same applies to the p-side electrode portion in other II-VI group compound semiconductor light emitting diodes or II-VI group compound semiconductor elements. I have a problem.

In view of the above points, the present invention solves the problem of contact resistance, the problem of operating voltage, the problem of manufacturing the electrode part, etc. in the electrode part, especially the p-side electrode part in the II-VI group compound semiconductor device. The present invention provides a semiconductor device made of a II-VI group compound semiconductor that can be manufactured.

[0015]

In the semiconductor device according to the first aspect of the present invention, the p-side electrode portion 21 for the II-VI group compound semiconductor element is a ZnT on the II-VI group compound semiconductor element 13.
e _x Se _1-x layer 22 and ZnTe formed on it
The layer 23 and the metal electrode 9 in ohmic contact with the ZnTe layer 23 are provided. A second invention is the semiconductor device according to the first invention, wherein ZnTe _x
The x value of the composition of the Se _1-x layer 22 is 0.01 ≦ x ≦ 0.15.
Select and configure within the range.

A third aspect of the invention is the semiconductor device of the first or second aspect, wherein the film thickness d of the ZnTe _x Se _{1- x} layer 22 is selected within the range of 5Å ≦ d ≦ 500Å.

A fourth invention is the method according to the first, second or third invention, wherein the uppermost layer of the II-VI group compound semiconductor device 13 is Z.
It is configured as the nSe layer 11.

The fifth aspect of the invention is the first, second, third or fourth aspect.
In the semiconductor device of the present invention, the II-VI group compound semiconductor element is configured as a semiconductor light emitting element such as a light emitting diode or a semiconductor laser.

A sixth aspect of the invention is the semiconductor device of the first, second, third, fourth or fifth aspect of the invention, in which the II-VI group compound semiconductor element is formed on the GaAs substrate 1.

A seventh invention is the semiconductor device of the first, second, third, fourth or fifth invention, wherein the II-VI group compound semiconductor element is formed on the n-type GaAs substrate 1. And

[0021]

According to the present invention, the p-side electrode portion 21 for the II-VI group compound semiconductor device is provided in the II-VI group compound semiconductor device 1.
ZnTe _x Se _1-x layer 22 on 3 and ZnT on it
Since it is composed of the e layer 23 and the metal electrode 9 which is in ohmic contact with the ZnTe layer 23, as shown in the energy band diagram of FIG.
The holes h injected into the II-VI group compound semiconductor device 13 are injected through the trap level of Te existing in the ZnTe _x Se _1-x layer 22. That is, by interposing the ZnTe _x Se _1-x layer 22 between the semiconductor element 13 and the ZnTe layer 23, the barrier against the holes h becomes low and thin, and the probability of hole tunneling increases. In particular, the probability of hole tunneling is further increased via the trap level of Te, and the current easily flows.

Therefore, the ohmic characteristics of the p-side electrode portion 21 are improved, the contact resistance of the p-side electrode portion 21 is reduced, and the operating voltage can be reduced.
The ZnTe _x Se _1-x layer 22 and the ZnSe layer 23 are formed by
It is obtained by subsequent growth on the II-VI group compound semiconductor device 13 produced by MBE, MOCVD or the like, and the production becomes easy.

In the second invention, the ZnTe _x Se _1-x layer 2 is formed.
By selecting the x value of 2 to be 0.01 ≦ x ≦ 0.15, it is possible to secure good ohmic characteristics of the p-side electrode portion 21. When the x value is less than 0.01, the trap level density is low, and when the x value is more than 0.15, ZnTe _x Se.
The crystallinity of the _1-x layer deteriorates, and in any case, the ohmic characteristics deteriorate.

In the third invention, the ZnTe _x Se _1-x layer 2 is formed.
By selecting the film thickness d of 2 in the range of 5Å ≦ d ≦ 500Å, good ohmic characteristics of the p-side electrode portion 21 can be secured. When the film thickness d exceeds 500 Å, holes are trapped in the trap level and the resistance becomes high, and the ohmic characteristic is deteriorated. When the film thickness d is less than 5 Å, the trap level is small and improvement of the ohmic characteristic cannot be expected.

In the fourth invention, since the uppermost layer of the II-VI group compound semiconductor device 13 is the ZnSe layer 11, this Zn
ZnSe _x Se _1-x layer 22 is sandwiched on the Se layer 11 to form Zn.
As shown in the potential diagram of FIG. 2, the Te layer 23 is formed, and the barrier against holes between the ZnSe layer 11 and the ZnTe layer 23 is a II-VI group compound semiconductor other than ZnSe, such as Z.
Compared to the case where nSSe or ZnMgSSe is used as the uppermost layer of the II-VI group compound semiconductor device 13, the thickness becomes lower and the probability of hole tunneling from the ZnTe layer 23 to the ZnSe layer 11 increases, and good ohmic characteristics are obtained. To be

According to a fifth aspect of the invention, in the semiconductor device of the first, second, third or fourth aspect of the invention, the II-VI group compound semiconductor element is a semiconductor light emitting element, so that low voltage and low power consumption are achieved. A II-VI group compound semiconductor light emitting device capable of performing the above operation can be obtained.

In the sixth aspect of the present invention, since the II-VI group compound semiconductor device is formed on the GaAs substrate 1, a GaAs substrate having a high crystal quality can be obtained at a relatively low cost. The crystal quality of the —VI compound semiconductor layer is also improved, and the II-VI compound semiconductor element can be operated with low current and low power consumption, and deterioration is suppressed.

In the seventh invention, the II-VI group compound semiconductor device is formed on the n-type GaAs substrate 1, so that there is no barrier between the substrate and the epitaxial layer of the II-VI compound semiconductor device. Electrons can be injected from the substrate side, and the operating voltage can be reduced.

[0029]

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

This example is applied to a semiconductor light emitting device, for example, a semiconductor laser. In this example, as shown in FIG. 1, a substrate 1 made of, for example, Si-doped n-type single crystal GaAs is prepared. An n-type buffer layer 2 made of, for example, ZnSe is epitaxially formed on one main surface of the n-GaAs substrate 1, and subsequently, a first cladding layer 3 made of Cl-doped n-type ZnMgSSe: Cl is sequentially formed. ZnSSe first guide layer 4, ZnCdSe
An active layer 5 of ZnSSe, a second guide layer 6 of ZnSSe,
For example, the second cladding layer 7 of p-type ZnMgSSe: N doped with nitrogen N, and the p-type intermediate layer 8 of ZnSSe: N having a buffer effect and a cladding effect as necessary.
Via the nitrogen, the cap layer 11 made of p-type Zn (S) Se: N doped with nitrogen N is epitaxied to form the semiconductor element portion 1.
3. In this example, the semiconductor laser section is formed.

Then, the p-side electrode portion 21 is formed on the semiconductor element portion 13. The p-side electrode portion 21 is formed on the cap layer 11 and is followed by nitrogen N-doped p-type ZnTe _x Se.
_1-x : the first semiconductor thin layer 22 by the N layer, and the nitrogen N on it
A second semiconductor thin layer 23 made of a doped p-type ZnTe: N layer is sequentially epitaxially grown, and the second semiconductor thin layer 2 is formed.
A metal electrode 9 made of, for example, an Au alloy, for example, an Au alloy containing Pd and Pt, is ohmic-contacted on the metal layer 3. On the other main surface of the substrate 1,
For example, the other electrode 10 made of In is ohmic-contacted.

Impurities for realizing p-type are group I, V
A group element is used, for example, nitrogen or lithium is used.

Each p-type Z forming the p-side electrode portion 21
nTe _x Se _1-x : a first semiconductor thin layer 22 composed of an N layer, p
The second semiconductor thin layer 23 formed of a ZnTe: N layer of the type is a semiconductor layer constituting the semiconductor element portion 13, for example, MB of the semiconductor layers 2, 3, 4, 5, 6, 7, 8, 11 in FIG.
It can be formed by continuous epitaxy subsequent to epitaxy by E, MOCVD, or the like.

P-type ZnTe _x Se _{1-x of} the first semiconductor layer
The thin layer 22 has a composition x value of 0.01 ≦ x ≦ 0.15.
The composition is selected in the range. If the x value is less than 0.01, the density of the trap level described below becomes low, and if the x value exceeds 0.15, the crystallinity of p-type ZnTe _x Se _1-x becomes poor. However, the ohmic characteristics of the p-side electrode portion are lost.

P-type ZnTe _x Se _{1-x of} the first semiconductor layer
The film thickness d of the thin layer 22 is selected so that 5Å ≦ d ≦ 500Å.
When the film thickness d exceeds 500 Å, it is captured by the trap level, the p-side electrode portion 21 has a high resistance, and the ohmic characteristics deteriorate. Further, if the film thickness d is less than 5Å, the trap level decreases and the ohmic characteristics cannot be improved.

The first semiconductor layer 22 and the second semiconductor layer 23
May contain a trace amount of impurities (for example, impurities originally contained in the raw material).

Next, the operation of the p-side electrode portion 21 having the above structure will be described with reference to the energy band structure shown in FIG.

It is generally known that the p-type ZnTe _x Se _1-x layer 22 has a trap level 25 of Te (Te cluster or the like). T in this ZnTeSe
The trap level due to e is 270 to 510 above the valence band.
mVe. This is 270 to 510 m from the band edge emission in PL (photoluminescence) measurement.
Since it is known that light with a low eV energy is emitted, it is considered that the trap level due to Te exists on the valence band side. In the present invention, the trap level due to Te contributes to the improvement of the ohmic characteristics of the p-side electrode portion 21.

That is, in FIG. 2, the p-type ZnTe layer 23 and the p-type Z
The holes h injected from the metal electrode 9 into the p-type ZnTe layer 23 are the p-type as shown by the apex E _V of each valence band of each energy band of the nTe _x Se _1-x layer 22 and the p-type ZnSe. It is injected into the p-type ZnSe layer 11 which is the uppermost cap layer of the semiconductor element portion 13 through the trap level 25 of Te existing in the ZnTe _x Se _1-x layer 22. That is, the ZnTe _x Se _1-x layer 2 having a film thickness d of 5Å ≦ d <500Å between the ZnTe layer 23 and the ZnSe layer 11 is formed.
With the interposition of 2, the barrier against the holes h becomes low and thin, and the probability of tunneling of the holes h shown by the arrow a in FIG. 2 increases. In particular, the tunnel probability of the holes h is further increased through the trap level 25 of Te, and the current easily flows. As a result, the ohmic property of the p-side electrode portion 21 is improved, the contact resistance is reduced, and the operating voltage is sufficiently reduced.

Incidentally, the p-type ZnSe layer 1 as the uppermost layer of the device
In the case of the p-side electrode portion 14 of FIG. 4 in which the p-type ZnTe layer 12 and the metal electrode 9 are laminated on the valence electron 1, the valence electrons of each energy band of the p-type ZnTe layer 23 and the p-type ZnSe layer 22 are shown in FIG. A simple ZnTe / Zn, as shown by the apex Ev of the band
In the Se junction, since the barrier against the holes h is high and thick, the tunnel probability of the holes h shown by the arrow a is low, and the current hardly flows. Therefore, as compared with the present embodiment, the required injection amount of the holes h cannot be achieved at a lower voltage, and the operating voltage cannot be sufficiently reduced.

As described above, according to this embodiment, II-
In the group VI compound semiconductor laser, its p-side electrode portion 21
On the uppermost p-type ZnSe layer 11 of the semiconductor element part, p
-Type ZnTe _x Se _1-x layer 22 and p-type ZnTe layer 23 are stacked by crystal growth, and the metal electrode 9 is deposited thereon, whereby the resistance of the p-side electrode portion 21 is reduced, A laser oscillation operation can be performed at lower voltage and lower power consumption.

Further, the element portion 13 is formed by MBE, MOCVD, etc., and then p-type ZnTe _x Se is formed.
_{Since the 1-x} layer 22 and the p-type ZnTe layer 23 may be crystal-grown, the p-side electrode portion 21 can be easily manufactured.

Further, since the contact resistance in the p-side electrode portion 21 is reduced, the deterioration of the semiconductor laser due to the heat generation of the p-side electrode portion 21 is reduced.

In the above example, the II-VI group compound semiconductor layers (2 to 23) were epitaxially grown on the GaAs substrate 1, but they may also be epitaxially grown on a III-V group compound substrate such as InP.

In the above example, the p-side electrode portion 21 of the present invention is used.
It was applied to II-VI group compound semiconductor lasers.
It can also be applied to the p-side electrode portion of other II-VI compound semiconductor devices such as -VI compound semiconductor light emitting diodes.

[0046]

According to the constitution of the present invention, in the II-VI group compound semiconductor device, the p-side electrode portion is made of ZnTe _x Se.
By stacking a _1-x layer and a ZnTe layer and forming a metal electrode on top of this by ohmic contact, the resistance of the p-side electrode part is reduced, and operation at low voltage and low power consumption is possible. To In particular, by providing the ZnTe _x Se _1-x layer, the tunnel level of holes is increased by the trap level of Te existing in ZnTeSe, and the resistance of the p-side electrode portion can be reduced.

Further, the p-side electrode portion is continuously formed on the device by Zn
Since the Te _x Se _1-x layer and the ZnTe layer can be produced by crystal growth, the p-side electrode portion can be easily produced.

Further, since the contact resistance of the p-side electrode portion becomes small, deterioration of the semiconductor device due to heat generation in the p-side electrode portion can be reduced.

By setting the x value of the ZnTe _x Se _1-x layer to 0.01 ≦ x ≦ 0.15, good ohmic characteristics of the p-side electrode portion can be secured.

Further, the film thickness d of the ZnTe _x Se _1-x layer is set to 5
By setting Å ≦ d ≦ 500Å, good ohmic characteristics of the p-side electrode portion can be secured.

The uppermost layer of the II-VI group compound semiconductor device is made of Zn.
By using the Se layer, ZnTe _xSe_1-xSandwich the layers
Has a low barrier against holes between the ZnSe layer and the ZnTe layer.
It also becomes thinner and secures good ohmic characteristics.
it can.

By using the II-VI group compound semiconductor element as a semiconductor light emitting element, it is possible to provide a II-VI group compound semiconductor light emitting device capable of operating at low voltage and low power consumption.

By forming the II-VI group compound semiconductor device on the GaAs substrate, a GaAs substrate having high crystal quality can be obtained at a relatively low cost. Therefore, the II-VI group compound semiconductor layer grown on the GaAs substrate can be formed. The crystal quality is improved, the II-VI group compound semiconductor device can be operated with low current and low power consumption, and deterioration is suppressed.

A II-VI group compound semiconductor device is replaced by an n-type GaA
By forming it on the s substrate, electrons without a barrier can be injected from the substrate side between the substrate and the epitaxial layer of the II-VI group compound semiconductor device, and the operating voltage can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a semiconductor device according to the present invention.

FIG. 2 is an energy band model diagram of a p-side electrode portion of a semiconductor device according to the present invention.

FIG. 3 is an energy band model diagram of a p-side electrode portion of a semiconductor device according to a conventional example.

FIG. 4 is a schematic cross-sectional view showing an example of a conventional semiconductor device.

FIG. 5 is a schematic cross-sectional view showing another example of a conventional semiconductor device.

[Explanation of symbols]

1 GaAs substrate 2 ZnSe buffer layer 3 First ZnMgSSe: Cl clad layer 4 First ZnSSe guide layer 5 ZnCdSe active layer 6 Second ZnSSe guide layer 7 Second ZnMgSSe: N clad layer 8 ZnSSe: N intermediate layer 9 Metal electrode 10 Other electrode 11 Zn (S) Se: N cap layer 13 Semiconductor element portion 21 p-side electrode portion 22 ZnTe _x Se _1-x : N layer 23 ZnTe: N layer

Claims (7)

[Claims] 1. The ZnTe _x on the II-VI group compound semiconductor device is a p-side electrode portion for the II-VI group compound semiconductor device.
A semiconductor device comprising a Se _1-x layer, a ZnTe layer formed on the Se _1-x layer, and a metal electrode in ohmic contact on the ZnTe layer. 2. The semiconductor device according to claim 1, wherein the x value of the composition of the ZnTe _x Se _1-x layer is 0.01 ≦ x ≦ 0.15. 3. The film thickness d of the ZnTe _x Se _1-x layer is:
5. The semiconductor device according to claim 1, wherein 5Å ≦ d ≦ 500Å. 4. The semiconductor device according to claim 1, wherein the uppermost layer of the II-VI group compound semiconductor element is a ZnSe layer. 5. The semiconductor device according to claim 1, wherein the II-VI group compound semiconductor element is a semiconductor light emitting element. 6. The II-VI group compound semiconductor device is GaA.
It is formed on an s substrate.
The semiconductor device according to 2, 3, 4 or 5. 7. The semiconductor device according to claim 1, wherein the II-VI group compound semiconductor element is formed on an n-type GaAs substrate.