JPH09260786A - Semiconductor light emitting element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict lamination defects and give longer life by forming a defect restricting layer by one atomic layer or more, having a group II element and a group V element at the interface between a III-V compound semiconductor substrate and a II-VI compound semiconductor crystal. SOLUTION: At the interface between a III-V compound semiconductor substrate 11 and II-VI semiconductor crystals 12 to 20, a defect restricting layer 12 crystallized in a group II element and a group V element is formed. Here, as the group II element, it is desired to be either Zn, Cd, Be or Mg, and as the V group element, it is desired to be one among N, P, As and Sb. The II-VI compound semiconductor crystals 12 to 22 produced on the defect restricting layer 12 are ready to form a secondary growth from an early stage of growth, and the occurrence of lamination defect can be restricted. This defect restricting layer 12 is formed by simultaneous or alternating supply of the raw material of group II element and the raw material of group V element. At this time, it is desirable that the top surface of the III-V semiconductor compound substrate 11 become a stabilized surface or an excessive surface of the group V element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device such as a light emitting diode in the blue to green region, a semiconductor laser and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In order to increase the density of optical discs such as digital video discs (DVDs), it is essential to shorten the wavelength of the semiconductor laser used as the light source. In recent years, a ZnSe-based material that is a II-VI group compound semiconductor has realized a semiconductor laser in the blue-green region that continuously oscillates at room temperature. The structure uses GaAs which is a III-V group compound semiconductor for the substrate and ZnMgS for the cladding layer.
Se, ZnCdSe is used for the active layer (see, for example, Literature Electronics Letters / Electronics
Letters 29 (1993) p1488).

However, the semiconductor laser using these II-VI group compound semiconductors has a device lifetime of several hours, and it is necessary to improve the lifetime to several thousand hours in order to put the optical disk device into practical use. there were.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The cause of limiting the life of the I-VI group compound semiconductor laser is considered as follows. II such as GaAs
At the interface between the IV compound semiconductor substrate and the ZnSe-based II-VI compound semiconductor crystal, a Ga ₂ Se ₃ compound is usually formed by the formation of a bond between Ga and Se. ZnSe-based crystals grow three-dimensionally on this Ga ₂ Se ₃ compound, and as a result, I
Stacking faults occur in the I-VI group compound semiconductor crystal.
During the laser operation, a defect called a dark spot is generated at the point where the stacking fault penetrates the active layer of the laser structure, and from this, the laser element is deteriorated. Conventionally, II-VI
The density of stacking faults generated in a group compound semiconductor crystal is 10
⁴ cm- ² or more, in order to make the semiconductor laser lifetime thousands hours are necessary to the defect density in the 10 ² cm- ² or less.

Therefore, an object of the present invention is to provide a semiconductor light emitting device such as a semiconductor laser having a long life by suppressing stacking faults generated from the interface between the III-V group compound semiconductor substrate and the II-VI group compound semiconductor crystal. It is to be realized.

[0006]

According to the present invention, a defect suppressing layer made of a crystal composed of a group II element and a group V element is provided at the interface between a group III-V compound semiconductor substrate such as GaAs and a group II-VI compound semiconductor crystal. Form. Here, the group II element is preferably Zn, Cd, Be or Mg, and the group V element is preferably N, P, As or Sb. The II-VI group compound semiconductor crystal produced on this defect suppression layer can be two-dimensionally grown from the initial stage of growth, and the occurrence of stacking faults is suppressed. This defect suppression layer is formed by supplying the group II element raw material and the group V element raw material simultaneously or alternately. At this time, it is desirable that the outermost surface of the III-V compound semiconductor substrate be a stabilizing surface or an excess surface of the V group element in order to suppress the generation of the GaSe compound that is a single crystal. Here, the thickness of the defect suppression layer is 1 atomic layer (0.5 nm) or more and 10 nm.
The following is desirable, and particularly preferably 1 to 5 nm
Range. As the layer becomes thicker, lattice defects are generated. Moreover, the electric resistance also increases, which is not preferable.

When these defect suppressing layers are formed at a substrate temperature of 400 ° C. or higher, the constituent elements of the III-V group compound semiconductor substrate and the II-VI group compound semiconductor crystal mutually diffuse. As a result, the electrical characteristics of the manufactured semiconductor light emitting device deteriorate at the substrate interface. Therefore,
The defect suppression layer needs to be formed at a low substrate temperature of 100 to 400 ° C.

In forming these defect suppressing layers, II
By supplying atomic hydrogen or hydrogen radicals at the same time as at least one of the group element raw material and the group V element raw material, it is possible to form a defect suppression layer having good crystallinity at a low substrate temperature of 100 to 400 ° C. Become. Also,
When a nitrogen radical is used as the group V element raw material, the substrate temperature is set to 1 without introducing atomic hydrogen or hydrogen radical.
It is possible to form a good defect suppressing layer at a low temperature of 00 to 400 ° C.

[0009]

Embodiments of the present invention will be described in detail below.

FIG. 1 shows a semiconductor laser structure of a first embodiment of the present invention. This structure was grown on a GaAs substrate by the molecular beam epitaxy (MBE) method. First, in the substrate pretreatment chamber of the MBE apparatus, n-type G
The aAs substrate 11 was heated to 600 ° C. to remove the oxide film. After that, the substrate temperature was lowered to 300 ° C. and the supply of As molecular beam was stopped. At this time, reflection high-energy electron diffraction (R
It was confirmed by HEED) that the surface of the GaAs substrate 11 was an As-excessive surface.

Next, the substrate surface was irradiated with hydrogen radicals at a substrate temperature of 300 ° C. for 1 minute. Hydrogen radical is E
It was generated by introducing hydrogen gas into a CR (electron cyclotron resonance) type activation cell and applying ECR power. The conditions at this time are as follows: growth chamber pressure 1 × 10 ⁻³ P
a, ECR power was 100W. Further, the As molecular beam and the Zn molecular beam were alternately supplied (each 10 seconds) for 3 cycles while irradiating with hydrogen radicals. X-ray photoelectron spectroscopy (XP
S) As a result of the measurement, there is no bond between Ga and Se on the GaAs substrate surface thus pretreated,
Defect suppression layer 12 composed of a compound of As and Zn and having a few atomic layers
The formation of was confirmed.

After that, the substrate is mounted on the II-VI in the MBE device.
After moving to the group-semiconductor crystal growth chamber and at a substrate temperature of 300 ° C., an n-type ZnSe buffer layer (50 nm) 13, an n-type Z
nMgSSe clad layer (1.5 μm) 14, n-type Zn
SSe light guide layer (80 nm) 15, ZnCdSe active layer (7 nm) 16, p-type ZnSSe light guide layer (80 n
m) 17, p-type ZnMgSSe cladding layer (1.0 μm
m) 18, p-type ZnSe layer (100 nm) 19, p-type Z
The nSeTe contact layer (100 nm) 20 was sequentially laminated. Chlorine was doped as the n-type donor. Further, nitrogen radicals generated by the activation cell were used for p-type doping. Where 14, 15, 17, 18
The lattice constant of each layer is the same as that of the GaAs substrate. The band gaps of the cladding layers 14 and 18 are about 2.9e at room temperature.
V, the bandgap of the active layer 16 is about 2.4 eV. The Se composition of the contact layer 20 changes from 1 to 0 from the substrate side toward the surface.

The produced crystal was taken out from the MBE apparatus,
Si is formed on the contact layer 20 by an ordinary CVD technique.
After forming the O ₂ film 21, a stripe hole of about 20 μm was formed by the photolithography technique, and the Au / Pt / Ti / Ni electrode 22 was formed as the p electrode by the vacuum evaporation method. Further, an Au / Ge / Ni electrode 2 is formed on the back surface as an n electrode.
After forming No. 3, it was cleaved to a length of about 1 mm. The semiconductor laser thus produced has a defect density in the active layer are reduced to 10 ² cm- ² or less, the life at room temperature continuous oscillation operation was not less than 3000 hours.

FIG. 2 shows a semiconductor laser structure according to the second embodiment of the present invention. This structure was grown on a GaAs substrate by the molecular beam epitaxy (MBE) method. First, in the substrate pretreatment chamber of the MBE apparatus, n-type G
The aAs substrate 11 was heated to 600 ° C. to remove the oxide film. After that, the substrate temperature was lowered to 300 ° C. and the supply of As molecular beam was stopped. At this time, reflection high-energy electron diffraction (R
It was confirmed by HEED) that the surface of the GaAs substrate 31 was an As-excessive surface.

Next, the substrate is moved to a II-VI group semiconductor crystal growth chamber in the MBE apparatus, and at a substrate temperature of 300 ° C., nitrogen radicals and Zn molecular beams are alternately supplied (each 10 seconds).
Was carried out for 3 cycles. Nitrogen radicals are produced by introducing nitrogen gas into an ECR (electron cyclotron resonance) type activation cell,
It was generated by applying ECR power. The conditions at this time are as follows: growth chamber pressure 1 × 10 ⁻³ Pa, ECR power 10
It was 0W. As a result of X-ray photoelectron spectroscopy (XPS) measurement, on the surface of the GaAs substrate thus pretreated, there is no bond between Ga and Se, and defects in several atomic layers made of a compound of N and Zn. The formation of the suppression layer 24 was confirmed.

After that, at a substrate temperature of 300 ° C., the n-type ZnSe buffer layer (50 nm) 13 and the n-type ZnMgS are formed.
Se clad layer 14 (1.5 μm), n-type ZnSSe optical guide layer (80 nm) 15, ZnCdSe active layer 16
(7 nm), p-type ZnSSe optical guide layer (80 nm) 1
7, p-type ZnMgSSe clad layer (1.0 μm) 1
8, p-type ZnSe layer (100 nm) 19, p-type ZnSe
Te contact layers (100 nm) 20 were sequentially stacked.
Chlorine was doped as the n-type donor. Also, p
Nitrogen radicals generated by the activation cell were used for the type doping. Here, the lattice constants of the layers 14, 15, 17, and 18 are the same as those of the GaAs substrate. The band gaps of the clad layers 14 and 18 are about 2.9 eV at room temperature, and the band gap of the active layer 16 is about 2.4 eV. The Se composition of the contact layer 20 changes from 1 to 0 from the substrate side toward the surface.

The produced crystal was taken out from the MBE apparatus,
Si is formed on the contact layer 20 by an ordinary CVD technique.
After forming the O ₂ film 21, a stripe hole of about 20 μm was formed by the photolithography technique, and the Au / Pt / Ti / Ni electrode 22 was formed as the p electrode by the vacuum evaporation method. Further, an Au / Ge / Ni electrode 2 is formed on the back surface as an n electrode.
After forming No. 3, it was cleaved to a length of about 1 mm. The semiconductor laser thus produced has a defect density in the active layer are reduced to 10 ² cm- ² or less, the life at room temperature continuous oscillation operation was not less than 3000 hours.

In the above embodiment, I was directly formed on the GaAs substrate.
Although the case of growing a group I-VI compound semiconductor crystal has been described, the case where a group III-V compound semiconductor crystal layer is first formed as a buffer layer on a GaAs substrate is also described.
At the interface between the buffer layer and the II-VI group compound semiconductor crystal formed thereon, a defect suppression layer similar to that of the above-mentioned embodiment may be formed.

[0019]

As described above, according to the present invention, I
Generation of stacking faults in the I-VI group compound semiconductor crystal can be suppressed. Therefore, when a semiconductor light emitting device in the blue to green region is prepared using a II-VI compound semiconductor crystal, it becomes possible to realize a semiconductor light emitting device having a long life.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor laser according to an embodiment of the present invention.

[Explanation of symbols]

11 ... n-type GaAs substrate 12 ... ZnAs defect suppression layer 13 ... n-type ZnSe buffer layer 14 ... n-type ZnMgSSe cladding layer 15 ... n-type ZnSSe light guide layer 16 ... ZnCdSe active layer 17 ... p-type ZnSSe light guide layer 18 ... p Type ZnMgSSe clad layer 19 ... p type ZnSe layer 20 ... p type ZnSeTe contact layer 21 ... SiO ₂ film 22 ... Au / Pt / Ti / Ni electrode 23 ... Au / Ge / Ni electrode 24 ... ZnN defect suppression layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Goto 1-280, Higashi Koikeku, Kokubunji, Tokyo, Central Research Laboratory, Hitachi, Ltd. (72) Shinichi Nakatsuka 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi, Ltd. Central Research Center

Claims (6)

[Claims] 1. A semiconductor light emitting device comprising a II-VI group compound semiconductor formed on a III-V group compound semiconductor substrate, comprising a III-V group compound semiconductor substrate and a II-VI group.
A semiconductor light emitting device, wherein at least one atomic layer or more of a defect suppressing layer containing a group II element and a group V element is formed at an interface of a group compound semiconductor crystal. 2. A defect suppression layer having a group II element and a group V element by simultaneously or alternately supplying a group II element raw material and a group V element raw material.
The manufacturing method of the semiconductor light emitting device according to the above. 3. A semiconductor light emitting device according to claim 1, wherein the defect suppressing layer made of a group II element and a group V element is formed at a substrate temperature of 100 ° C. or higher and 400 ° C. or lower. Method. 4. A defect suppressing layer comprising a group II element and a group V element is formed on a group V element stabilizing surface or a group V element excess surface of a group III-V compound semiconductor substrate. 1. The method for manufacturing a semiconductor light emitting device according to any one of 1 to 3. 5. A semiconductor light-emitting device manufacturing method according to claim 2, wherein atomic hydrogen or hydrogen radicals are supplied simultaneously with at least one of the group II element raw material and the group V element raw material. Method for manufacturing light emitting device. 6. The method for manufacturing a semiconductor light emitting device according to claim 2, wherein a nitrogen radical is supplied as a group V element raw material.