JP3334598B2 - II-VI compound semiconductor thin film on InP substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a group VI compound semiconductor thin film.

[0002]

2. Description of the Related Art A group III element such as Al, Ga, In or the like, and A
Semiconductor lasers having wavelengths in the infrared to red region, light emitting diodes in the yellow-green region, and the like have been put to practical use by III-V compound semiconductors composed of group V elements such as s, P, and Sb. However, in order to emit light at a shorter wavelength than this, a wider band gap is required, and it is difficult to realize the above-mentioned III-V group compound semiconductor.

On the other hand, Be, Mg, Mn, Zn, C
II-VI compound semiconductors comprising a group II element such as d and Hg and a group VI element such as S, Se and Te have a relatively large band gap and emit light at almost all wavelengths in the visible region. Is possible. For this reason, II-VI group compound semiconductors are expected as light emitting device materials particularly in the green to ultraviolet regions, and are being actively researched and developed at present.

In the production of the above-mentioned II-VI compound semiconductor thin film, it is difficult to obtain a high-quality II-VI bulk substrate crystal. A crystal is used as a substrate. When InP is used as the III-V group substrate, ZnCdSe, ZnSeT
e, MgZnCdSe and MgZnSeTe can be used to produce double heterostructures under lattice matching conditions, and light emitting devices using these have been reported (for example, Proceedings of the 58th JSAP Scientific Lecture Meeting) , N
o. 1, 277, 2a-V-1, 1997).

[0005]

However, when, for example, MgZnSeTe is grown on an InP substrate by molecular beam epitaxy (MBE), Te and S
e are hardly uniformly mixed with each other, and composition fluctuations and phase separation are likely to occur in mixed crystals. Such a composition fluctuation and phase separation are not desirable in application to a light emitting device, and cause an increase in device resistance and a decrease in luminous efficiency.

FIG. 4 shows a layer structure of a conventional II-VI compound semiconductor thin film grown on an InP substrate by MBE. I
When growing a II-VI compound semiconductor thin film on the nP substrate 1 by the MBE method, first, the II
In the group III-V compound semiconductor growth chamber connected to the group VI compound semiconductor growth chamber, the natural oxide film on the surface of the InP substrate is removed under the P or As molecular beam. Next, InP or GaInAs is used to restore the flatness of the substrate surface.
Alternatively, a III-V group buffer layer 2 made of GaInAsP or the like is grown. Next, the substrate on which the III-V group buffer layer 2 was grown was transported to a II-VI group compound semiconductor growth chamber, and after the substrate temperature was stabilized at about 280 ° C., the MgZnSeTe layer 10 was grown ( For example, Blue Laser and Light Emitting Diode International Symposium (Chiba Univ.)
1996).

However, in the case of MgZnSeTe, in particular, S
As the e composition increases, the tendency for phase separation to occur in a mixed crystal increases, for example, a phenomenon in which the band gap energy measured by photoluminescence (PL) becomes significantly smaller than the band gap energy measured by light reflection. Was observed, and when applied to a light-emitting device, this caused an increase in device resistance and a decrease in luminous efficiency. further,
In particular, MgZnSeTe is a mixed crystal composed of two group II elements and two group VI elements, so that it is difficult to control the composition.
For example, there is a problem in reproducibility of composition control, which has been an obstacle in manufacturing a light emitting device.

Also, when growing a MgZnCdSe mixed crystal on an InP substrate, it is necessary to control the composition of Zn and Cd simultaneously with the Mg composition in order to lattice-match with the InP substrate. Was increasing. Instead of MgZnCdSe quaternary mixed crystal, MgS
MgZn using a superlattice of ZnCdSe
There are also reports of attempts to provide properties equivalent to CdSe quaternary mixed crystals (The 58th Annual Meeting of the Japan Society of Applied Physics, Proc. Of No. 1, 337, 3a-V-6, 1997).
Year). According to this method, the band gap can be controlled only by controlling the composition of the ternary mixed crystal of ZnCdSe, and by changing the ratio of the layer thicknesses of MgSe and ZnCdSe, so that the labor required for controlling the composition can be greatly reduced. Was expected.

However, according to the experimental results of the present inventors,
It has been found that MgSe has a lattice mismatch of about 0.6% with the InP substrate, and that the MgSe / ZnCdSe superlattice easily causes crystal defects due to lattice strain. Furthermore, Mg
Se is highly reactive, reacts with impurities during growth to form defects, or is oxidized in air to close.
The crystal quality of the gSe / ZnCdSe superlattice was inferior to that of the MgZnCdSe quaternary mixed crystal.

Therefore, an object of the present invention is to easily produce a uniform and high-quality II-VI compound semiconductor thin film without composition fluctuation or phase separation on an InP substrate with good controllability. Another object of the present invention is to produce a uniform and high quality II-VI group compound semiconductor thin film capable of producing a long-life, high-output optical device on an InP substrate with good reproducibility.

[0011]

The present inventor has made various studies to achieve the above object, and as a result, the following (1)
To (7) have been completed. (1) A II-VI compound semiconductor thin film on an InP substrate, wherein two types of II-VI ternary mixed crystal layers A and B are alternately laminated on the InP substrate. (2) The II-VI compound semiconductor thin film on an InP substrate according to (1), wherein each layer thickness of the II-VI ternary mixed crystal layers A and B is equal to or less than the critical thickness. (3) The thickness of each of the II-VI ternary mixed crystal layers A and B is less than or equal to the critical thickness, and the II-VI ternary mixed crystal layers A and B are each
The II-VI compound semiconductor thin film on an InP substrate according to (1), wherein the total thickness of the II-VI mixed crystal thin film made of the following is not more than the critical thickness. (4) The II-VI compound semiconductor thin film on an InP substrate according to (1) to (3), wherein the II-VI ternary mixed crystal layers A and B are lattice-matched with the InP substrate.

(5) The II-VI group ternary mixed crystal layers A and B are
nCdSe, MgZnSe, ZnSeTe, ZnST
e, MgSSe, MgSTe, CdSSe, CdST
e, BeZnTe, BeCdTe, BeCdSe, Be
MgTe, BeMgSe, BeMnSe, BeMnT
e, BeHgSe, BeHgTe, ZnMnSe, Mn
SSe, MnSTe, ZnHgSe, HgSTe and H
Two ternary mixed crystals selected from gSSe (1)-
(4) A group II-VI compound semiconductor thin film on an InP substrate.

(6) The II-VI group ternary mixed crystal layer A is made of MgZnS
The II-VI compound semiconductor thin film on an InP substrate according to any one of (1) to (5), wherein the e-layer is a II-VI ternary mixed crystal layer B is a ZnSeTe layer. (7) The II-VI ternary mixed crystal layer A is a MgZnSe layer,
Group II-VI ternary mixed crystal layer B is a ZnCdSe layer (1)-
(5) Group II-VI compound semiconductor thin film on InP substrate.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. [Embodiment 1] FIG. 1 shows an InP substrate II according to the present invention.
1 shows a basic layer structure of a group VI compound semiconductor thin film. In the semiconductor thin film of the present embodiment, a III-V group buffer layer 2 is deposited on an InP substrate 1 in a III-V group compound semiconductor growth chamber, and this is deposited via a vacuum transfer mechanism. And the II-VI ternary mixed crystal A layer 3 and B layer 4
Are alternately laminated.

Since a ternary mixed crystal is used for the II-VI ternary mixed crystal A layer 3 and the B layer 4, the lattice constant can be made closer to that of the InP substrate 1 as compared with the binary compound, and defects can be reduced. It becomes difficult to enter, and deterioration such as oxidation hardly occurs. Also,
With the above configuration, the II-
Compared with the case of growing a quaternary, quinary or hexagonal mixed crystal containing all the components of the group VI ternary mixed crystal A and B, composition fluctuation and phase separation are less likely to occur, and composition controllability is significantly improved. Therefore, the work becomes easy, and a high-quality II-VI compound semiconductor thin film with good reproducibility can be obtained.

[Embodiment 2] FIG. 2 shows a more specific layer structure of a II-VI compound semiconductor thin film on an InP substrate of the present invention. First, in a III-V compound semiconductor growth chamber, P
The natural oxide film on the surface of the InP substrate 1 was removed under irradiation with a molecular beam, and then an InP buffer layer 5 was grown. This substrate is transferred to a group II-VI compound semiconductor growth chamber via a vacuum transfer mechanism, and a ZnCdSe buffer layer 6 having a thickness of about 10 nm is deposited, and then a ZnSeTe layer 7 and a MgZnSe layer 8 are deposited.
Were alternately laminated for 500 periods.

When growing a mixed crystal containing Te on the InP substrate 1, In and Te are easily combined to form a three-dimensional nucleus. Therefore, in order to obtain a film with good flatness, ZnCdSe is required.
The buffer layer 6 is effective. Also, when growing a mixed crystal containing Mg on the InP substrate, Mg easily reacts with residual impurities on the surface and the like, so that the ZnCdSe buffer layer 6 is effective in obtaining a film with good flatness. Considering the crystal quality of the II-VI compound semiconductor layer laminated thereon, the thickness of the ZnCdSe buffer layer 6 is desirably not more than the critical thickness determined by the amount of lattice mismatch with the InP substrate. The composition of the ZnCdSe buffer layer 6 is InP
Composition Zn0.48Cd0.52Se lattice-matched to substrate
Is most desirable.

The thicknesses of the MgZnSe layer 7 and the ZnSeTe layer 8 are set to be equal to or less than the critical thickness so that crystal defects due to lattice mismatch with the InP substrate 1 do not occur. Specifically, the composition of the MgZnSe layer 7 is Mg0.7Zn0.3S
e, there is about -0.57% lattice mismatch with the InP substrate. Therefore, the layer thickness of the MgZnSe layer 7 was set to 1 nm, which is 40 nm or less, which is the critical thickness in this case. Also, ZnS
The composition of the eTe layer 8 is ZnSe0.4Te0.6 and InP
Since there is about + 1.0% lattice mismatch with the substrate,
The thickness of the ZnSeTe layer 8 is the critical thickness in this case, 2
The thickness was set to 1 nm which is equal to or less than 0 nm. Note that ZnCdSe, Mg
The critical film thickness of ZnSe and ZnSeTe changes depending on the magnitude of lattice mismatch with the InP substrate.
J. Cryst. Growth, 27, 118, reviewed by ws and Blakeslee
Page, 1974).

The pseudo-quaternary mixed crystal Z thus produced
nSe0.4Te0.6 / Mg0.7Zn0.3Se,
When the light reflection measurement of the quaternary mixed crystal Mg0.35Zn0.65Se0.7Te0.3 having the same composition as the pseudo-quaternary mixed crystal was performed, the oscillation of the Fabry-Perot interference of the reflection spectrum was started. It was confirmed that the wavelengths were almost the same, and the band gap energies of both were almost the same. In the PL measurement, the ZnSeTe / MgZnSe
The peak energy of the quasi-quaternary mixed crystal is almost equal to the band gap energy estimated by light reflection measurement, and a uniform II-VI compound without phase separation and composition fluctuation as seen in the quaternary mixed crystal MgZnSeTe It was confirmed that a semiconductor thin film was obtained. The above is because the quaternary mixed crystal Mg used in the conventional II-VI group light emitting device on the InP substrate was used.
Instead of ZnSeTe, the pseudo-quaternary mixed crystal ZnSeTe
/ MgZnSe can be used.

[Embodiment 3] In the present embodiment, the MgZn in Embodiment 2 is set so that the total thickness of the pseudo-quaternary mixed crystal layer ZnSeTe / MgZnSe is equal to or less than the critical thickness.
The Se layer 7 was changed to a composition Mg0.6Zn0.4Se having a lattice mismatch of about -1.0% with respect to the InP substrate.
As a result, the entire pseudo-quaternary mixed crystal was lattice-matched to the InP substrate, the generation of crystal defects due to the lattice mismatch was suppressed, and a high-quality II-VI compound semiconductor thin film was obtained.

[Embodiment 4] In the present embodiment, the composition of the ZnSeTe layer 8 in Embodiment 2 is changed to a composition ZnSe0.54Te0.46 which lattice-matches with the InP substrate.
The composition of the MgZnSe layer 7 in the second embodiment was changed to the composition Mg0.84Zn0.16Se that lattice-matches with the InP substrate. Thereby, generation of crystal defects due to lattice mismatch was completely eliminated, and a high-quality II-VI compound semiconductor thin film was obtained.

[Embodiment 5] In this embodiment, MgZn
A pseudo quaternary mixed crystal in which Se layers and ZnCdSe layers are alternately stacked will be described. FIG. 3 shows the specific In of the present invention.
1 shows a layer structure of a II-VI compound semiconductor thin film on a P substrate. First, the natural oxide film on the surface of the InP substrate 1 is removed under P molecular beam irradiation in a III-V compound semiconductor growth chamber.
An nP buffer layer 5 was grown. The substrate is transferred to a group II-VI compound semiconductor growth chamber via a vacuum transfer mechanism, and a ZnCdSe buffer layer 6 having a thickness of about 10 nm is deposited. Then, a MgZnSe layer 7 and a ZnCdSe layer 9 are alternately formed.
00 cycles were stacked.

When a mixed crystal containing Mg is grown on an InP substrate, Mg easily reacts with residual impurities on the surface.
The ZnCdSe buffer layer 6 is effective in obtaining a film with good flatness. The thickness of the ZnCdSe buffer layer 6 is:
Considering the crystal quality of the II-VI compound semiconductor layer laminated thereon, it is desirable that the thickness be equal to or less than the critical thickness determined by the amount of lattice mismatch with the InP substrate. Also, ZnCdSe
Most preferably, the composition of the buffer layer 6 is a composition Zn0.48Cd0.52Se that lattice-matches with the InP substrate.

The thicknesses of the MgZnSe layer 7 and the ZnCdSe layer 9 are set to be equal to or less than the critical thickness so that crystal defects due to lattice mismatch with the InP substrate 1 do not occur. Specifically, the composition of the MgZnSe layer 7 is Mg0.7Zn0.3S
e, there is about -0.57% lattice mismatch with the InP substrate. Therefore, the layer thickness of the MgZnSe layer 7 was set to 1 nm, which is 40 nm or less, which is the critical thickness in this case. Also, ZnC
The composition of the dSe layer 9 is Zn0.63Cd0.37Se and I
Since there is about + 1.0% lattice mismatch with the nP substrate, the layer thickness of the ZnCdSe layer 9 was set to 1 nm, which is 20 nm or less, which is the critical thickness in this case.

The pseudo quaternary mixed crystal Z thus produced
n0.63Cd0.37Se / Mg0.7Zn0.3S
e and 4 having the same composition as the pseudo quaternary mixed crystal
Original mixed crystal Mg0.35Zn0.465Cd0.185Se
When the light reflection measurement was performed, the two wavelengths at which the oscillation of the Fabry-Perot interference of the reflection spectrum started almost matched,
It was confirmed that the band gap energies of both were almost equal. Also, in the PL measurement, the ZnCdSe / M
The peak energy of the gZnSe pseudo quaternary mixed crystal is almost equal to the band gap energy estimated by light reflection measurement, and it is confirmed that a uniform II-VI compound semiconductor thin film without phase separation or composition fluctuation is obtained. Was done. The above results indicate that the quaternary mixed crystal ZnCdSe / MgZnSe can be used instead of the quaternary mixed crystal MgZnCdSe used in the conventional II-VI group light emitting device on the InP substrate.

[Embodiment 6] In the present embodiment, the pseudo quaternary mixed crystal layer ZnSeTe / MgZnSe of Embodiment 5 is used.
The MgZnSe layer 7 according to the fifth embodiment is applied to the InP substrate 1 by about-
Composition with lattice mismatch of 1.0% Mg0.6Zn0.4
Changed to Se. As a result, In the pseudo quaternary mixed crystal as a whole
Lattice matching was achieved with the P substrate, and generation of crystal defects due to lattice mismatch was suppressed, and a high-quality II-VI compound semiconductor thin film was obtained.

[Embodiment 7] In the present embodiment, the composition of the ZnCdSe layer 9 in the fifth embodiment is changed to a composition ZnSe0.54Te0.46 that lattice-matches with the InP substrate 1, and the composition of the MgZnSe layer 7 in the fifth embodiment is changed. In
Composition Mg0.84Zn0.16S lattice-matched with P substrate
e. Thereby, generation of crystal defects due to lattice mismatch was completely eliminated, and a high-quality II-VI compound semiconductor thin film was obtained.

In Embodiments 2 to 7, the thickness of each of the ternary mixed crystal layers constituting the pseudo quaternary mixed crystal is set to 1 nm, but by changing the ratio of the respective layer thicknesses, an arbitrary composition can be obtained. It is possible to realize a pseudo quaternary mixed crystal.
In this case, the thickness of the ternary mixed crystal layer constituting the pseudo quaternary mixed crystal is desirably equal to or less than the critical thickness determined by the amount of lattice mismatch with the substrate, and most preferably lattice matched with the substrate. desirable. In order to obtain a pseudo quaternary mixed crystal having a band gap close to that of a quaternary mixed crystal having an equivalent composition, it is necessary to use a pseudo quaternary mixed crystal.
Each layer thickness of the ternary mixed crystal layer constituting the ternary mixed crystal is about 5 nm.
It is desirable to make it below.

Also, MgSe is highly reactive and easily generates crystal defects, whereas MgZe used in the above embodiment is used.
In the nSe layer, crystal stability is increased by mixing Zn with MgSe, and a mixed crystal layer with few crystal defects can be easily obtained.

In the above embodiment, a pseudo-quaternary mixed crystal using ZnSeTe and MgZnSe on an InP substrate,
Also, a pseudo quaternary mixed crystal using ZnCdSe and MgZnSe has been described.
ZnSe, ZnSeTe, ZnSTe, MgSSe, M
gSTe, CdSSe, CdSTe, BeZnTe, B
eCdTe, BeCdSe, BeMgTe, BeMgS
e, BeMnSe, BeMnTe, BeHgSe, Be
HgTe, ZnMnSe, MnSSe, MnSTe, Z
The present invention can be applied to the production of pseudoquaternary, pseudoquinary or pseudoquaternary mixed crystals composed of any two of the ternary mixed crystals of nHgSe, HgSTe, and HgSSe. The effect is obtained irrespective of the conductivity type of the semiconductor layer and the type of the added impurity.

As the III-V compound semiconductor buffer layer on the InP substrate used in the above embodiment, in addition to InP, GaInAs, GaInAsP, AlInAs,
AlGaInP and a buffer layer obtained by combining them are conceivable. These are used for restoring the flatness of the surface of the InP substrate after removing the native oxide film and improving the quality of the II-VI compound semiconductor thin film laminated thereon. Although effective, the present invention is effective even without these III-V group buffer layers.

When a group III-V buffer layer other than InP is used, the layer thickness of the group III-V buffer layer is laminated on the buffer layer.
Considering the crystal quality of the II-VI compound semiconductor layer, InP
It is desirable that the thickness be equal to or less than the critical thickness determined by the amount of lattice mismatch with the substrate, and it is most desirable that the lattice match with the InP substrate be made. The ZnCdSe buffer layer is also effective for improving the quality of the II-VI compound semiconductor thin film laminated thereon, but the present invention is effective even without the ZnCdSe buffer layer. Further, ZnCdS
The present invention is also effective when another II-VI compound semiconductor is used as the buffer layer instead of the e-buffer layer. In this case, considering the crystal quality of the II-VI compound semiconductor layer laminated thereon, the layer thickness of the II-VI compound semiconductor buffer layer is equal to or less than the critical thickness determined by the amount of lattice mismatch with the InP substrate. And lattice matching with the InP substrate is most desirable. In the above embodiment, the method of manufacturing a II-VI group compound semiconductor thin film by the MBE method has been described. However, a metal organic chemical vapor deposition method (MOVPE method, MOCVD method) or another crystal growth method may be used. Good.

[0033]

As is apparent from the above description, according to the present invention, two types of II-VI ternary mixed layers are formed on an InP substrate or a III-V compound semiconductor buffer layer on an InP substrate. By alternately stacking crystal layers to produce a quaternary II-VI group pseudo-mixed crystal, a uniform and high-quality II-VI compound semiconductor thin film without phase separation or composition fluctuation can be obtained. In addition, a quaternary mixed crystal having an arbitrary composition can be obtained only by changing the layer thickness of the two types of ternary mixed crystals to be combined.
Composition controllability is significantly improved. Therefore, by using this semiconductor thin film, an optical device having a long life and high output can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a layer structure of a II-VI compound semiconductor thin film according to the present invention.

FIG. 2 is a diagram showing an example of a layer structure of a II-VI compound semiconductor thin film according to the present invention.

FIG. 3 is a diagram showing an example of a layer structure of a II-VI compound semiconductor thin film according to the present invention.

FIG. 4 is a diagram showing an example of a layer structure of a conventional II-VI group compound semiconductor thin film.

[Explanation of symbols]

 Reference Signs List 1 InP substrate 2 III-V group buffer layer 3 II-VI group ternary mixed crystal A layer 4 II-VI group ternary mixed crystal B layer 5 InP buffer layer 6 ZnCdSe buffer layer 7 MgZnSe layer 8 ZnSeTe layer 9 ZnCdSe layer 10 MgZnSeTe layer

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 33/00 H01L 21/20-21/208 H01L 21/36-21/368 H01S 5/00-5 / 50

Claims (7)

(57) [Claims] 1. A quasi- multi - element II-VI ternary mixed crystal layer having two or more II-VI ternary mixed crystal layers A and B alternately laminated on an InP substrate.
On an InP substrate characterized by forming a group VI mixed crystal
II-VI compound semiconductor thin film. 2. The In according to claim 1, wherein each of the II-VI ternary mixed crystal layers A and B has a thickness less than a critical thickness.
II-VI compound semiconductor thin film on P substrate. 3. The II-VI ternary mixed crystal layers A and B each have a thickness less than or equal to a critical thickness, and
Based mixed crystal layer A and quaternary or pseudo multiple group II-VI InP substrate II-VI compound semiconductor thin film according to claim 1 the total thickness of the mixed crystal thin film is equal to or less than the critical thickness consisting of B. 4. The II-VI group ternary mixed crystal layers A and B are In
4. The group II-VI compound semiconductor thin film on an InP substrate according to claim 1, which is lattice-matched with a P substrate. 5. The ternary II-VI mixed crystal layer A and B
nCdSe, MgZnSe, ZnSeTe, ZnST
e, MgSSe, MgSTe, CdSSe, CdST
e, BeZnTe, BeCdTe, BeCdSe, Be
MgTe, BeMgSe, BeMnSe, BeMnT
e, BeHgSe, BeHgTe, ZnMnSe, Mn
SSe, MnSTe, ZnHgSe, HgSTe and H
2. A ternary mixed crystal selected from gSSe.
5. A II-VI compound semiconductor thin film on an InP substrate according to any one of 4. 6. The InP according to claim 1, wherein the II-VI ternary mixed crystal layer A is a MgZnSe layer, and the II-VI ternary mixed crystal layer B is a ZnSeTe layer. On board II-
Group VI compound semiconductor thin film. 7. The InP according to claim 1, wherein the II-VI ternary mixed crystal layer A is a MgZnSe layer, and the II-VI ternary mixed crystal layer B is a ZnCdSe layer. On board II-
Group VI compound semiconductor thin film.