JPH09289171A - Surface treatment method of re-grown interface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To clean the surface of an As compound semiconductor, by a method wherein the surface of an As compound semiconductor which serves as a regrown interface is annealed in an atmosphere of AsH3 . SOLUTION: A substrate of AlAs, GaAs, AlGaAs, InAlAs or InGaAs which serves as a regrown interface of a compound semiconductor is made to rise in temperature from a room temperature to a prescribed range of temperature and annealed in an atmosphere of AsH3 for a prescribed time. At this point, AsH3 gas starts being fed to a growth chamber before the substrate reaches a prescribed temperature and keeps being fed until a regrowth is finished. Contaminants attached to the regrown interface are removed by this annealing process to lessen the regrown interface in interface level. Then, the substrate is increased in temperature to a prescribed regrown temperature, and AlGaAs or the like is regrown on the surface of the substrate of AlGaAs or the like through an organic metal vapor growth method.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to AlAs and Ga.
As, AlGaAs, InAlAs, InGaAs, I
The present invention relates to a surface treatment method for cleaning the regrowth interface and reducing the interface level when growing a compound semiconductor on the regrowth interface using the surface of nP, InAlP, InGaP or InGaAsP as the regrowth interface.

[0002]

2. Description of the Related Art On the surface of AlGaAs exposed to the atmosphere, Ga (gallium), Al (aluminum) and A
An oxide of s (arsenic) is formed and C (carbon) remains. Contamination by these oxides and carbon causes formation of high-density interface states at the regrowth interface when a compound semiconductor is regrown on this surface. Therefore, it is necessary to clean the surface as the regrowth interface to reduce the interface level. However, it is difficult to remove contaminants and sufficiently clean the surface only by performing a normal heat cleaning treatment.

Therefore, methods for removing surface contamination have been proposed. For example, Document 1: “Inst. Ph.
ys. Conf. Ser. , No129 (1992) 5
85 ”, the surface of AlGaAs is irradiated with ECR hydrogen plasma to remove oxides and carbon from the surface.

Reference 2: "J. Vac. Sci. T"
echnol. , A4 (1986) 677 ”,
GaAs and AlGa were produced by RIBE equipment using hydrogen and chlorine ions as sources in ECR plasma.
By etching the surface of As, the oxide and carbon on the surface are removed.

Further, Document 3: "Jpn. J. Appl.
Phys. , Vol 30 (1991) L322 ”, the surface of AlGaAs is treated with ammonium sulfide to remove surface contamination.

Incidentally, the same pollution as that generated on the surface of AlGaAs is caused by AlAs, GaAs, InAlAs, I.
nGaAs, InP, InAlP, InGaP or I
It also occurs on the surface of nGaAsP.

[0007]

SUMMARY OF THE INVENTION However, ECR
In order to perform plasma processing or RIBE etching, processing in an ultra-high vacuum is required. On the other hand, re-growth by the MOCVD method is performed under reduced pressure or normal pressure (for example, 50 to 760 T).
The pressure is about orr). A substrate such as AlGaAs whose surface has been cleaned by ECR plasma treatment or the like needs to be regrown without exposing the surface to the atmosphere.
Therefore, it is necessary to connect a device for performing ECR plasma processing and a device for performing regrowth (for example, a MOCVD growth device) to provide a complicated transport system. If such a transport system is provided, the configuration of the device becomes complicated, so that not only the maintenance including maintenance of the device becomes difficult, but also the versatility of the device is lost. It was

When ammonium sulfide treatment is performed, a large amount of sulfur adheres to the surface of the substrate such as AlGaAs. There is a concern that the sulfur may contaminate the reaction furnace of the apparatus for regrowing the compound semiconductor.

Therefore, it has been desired to realize a new surface treatment method for the regrowth interface which reduces the interface state of the regrowth interface.

[0010]

The inventor of the present application has proposed a method for reducing the interface state of a compound semiconductor.
Various methods of surface cleaning as a regrowth interface were studied and experiments were performed.

As a result, the following conclusions have been reached. Conventionally, AlAs, GaAs, AlGaAs, I
When re-growing As-based compound semiconductors on the surface of As-based compound semiconductors such as nAlAs and InGaAs, As is the composition component of these compound semiconductors is removed from the surface in the growth chamber of arsine. (As
H ₃ ) gas is introduced for regrowth, and similarly, InP, InAlP, InGaP and InGaAsP are also used.
When re-growing a P-based compound semiconductor on the surface of a P-based compound semiconductor such as the above, phosphine (PH ₃ ) gas is introduced to perform re-growth. On the other hand, it is known that AsH ₃ and PH ₃ are decomposed when heated at a certain temperature to generate hydrogen radicals.

Therefore, conventionally, a sample having a surface as a regrowth interface is heated from room temperature to an optimum temperature for regrowth, for example, 60.
The AsH ₃ gas or PH ₃ gas is introduced into the growth chamber before reaching a certain temperature, for example, 400 ° C., during which the temperature is linearly and continuously increased to an appropriate temperature within the range of 0 to 750 ° C. Therefore, by positively utilizing these AsH ₃ gas and PH ₃ gas, when these gases reach the temperature at which they are thermally decomposed to generate hydrogen radicals, the generated hydrogen radicals cause It was thought that the removal of the contamination would clean the surface as the regrowth interface and reduce the interface state of the regrowth interface. In short, when re-growing the compound semiconductor, the AsH ₃ gas or PH ₃ gas introduced into the growth chamber is used as it is, and before the actual re-growth, the surface as a re-growth interface is It was discovered that the surface of the compound semiconductor can be cleaned by performing AsH ₃ annealing or PH ₃ annealing. The invention of this application was made based on such findings.

Therefore, according to the first surface treatment method of the regrowth interface according to this application, AlAs, GaAs, AlGaAs, InAl as the regrowth interface of the compound semiconductor are used.
The surface of As or InGaAs is characterized by performing arsine (AsH ₃ ) annealing before starting the re-growth of the compound semiconductor.

The temperature at which AsH ₃ annealing is performed is A
This As temperature is higher than the temperature at which sH ₃ does not decompose.
The temperature is a temperature at which H ₃ is thermally decomposed and lower than the temperature at which the compound semiconductor is regrown.

In the stage before starting the re-growth in this way,
When AsH ₃ annealing is performed on the surface of AlAs, GaAs, AlGaAs, InAlAs or InGaAs, AsH ₃ is thermally decomposed to generate hydrogen radicals, and the hydrogen radicals remove the contamination of these surfaces, As a result, the interface level of the regrowth interface can be lowered.

Further, according to the second surface treatment method of the regrown interface according to the present application, AlAs, GaAs, AlGaAs, InAlA as the regrown interface of the compound semiconductor.
It is characterized in that hydrogen annealing and AsH ₃ annealing are performed in this order on the surface of s or InGaAs before starting the regrowth of the compound semiconductor.

According to this method, hydrogen annealing and AsH are performed.
Two-stage annealing, which is ₃ anneals, is performed, and to some extent AlAs, GaAs, A by hydrogen anneal.
The contamination of the surface of 1GaAs, InAlAs, or InGaAs is removed, and the bonding state of impurities such as oxides and carbon is made weak and unstable. Further, since the contamination of impurities whose surface bonding state is weakened by AH ₃ annealing can be removed, the interface level of the regrowth interface can be further lowered.

In the second surface treatment method for the regrown interface, it is preferable to perform phosphoric acid treatment on the regrown interface before hydrogen annealing. If the phosphoric acid treatment is performed on the regrown interface before hydrogen annealing, the surface as the regrown interface can be cleaned more favorably. When this phosphoric acid treatment is performed, the regrowth interface can be cleaned and the interface state of the regrowth interface can be lowered by hydrogen annealing in a shorter time than when the phosphoric acid treatment is not performed.

According to the third method for surface treatment of the regrown interface according to this application, InP, InAlP, InGaP or InGa as the regrown interface of the compound semiconductor is used.
It is characterized in that the surface of AsP is annealed with phosphine (PH ₃ ) before the regrowth of the compound semiconductor is started.

Similar to the case of AsH ₃ annealing, InP, InAlP, InGaP are used before the start of regrowth.
Alternatively, by performing PH ₃ annealing on the surface of InGaAsP, hydrogen radicals generated by thermal decomposition of PH ₃ can remove the contamination of these surfaces and reduce the interface level of the regrowth interface.

Further, according to the fourth method for surface treatment of a regrown interface according to this application, InP, InAlP, InGaP or InGa as a regrown interface of a compound semiconductor is used.
It is characterized in that the surface of AsP is subjected to hydrogen annealing and PH ₃ annealing in this order before starting the regrowth of the compound semiconductor.

In this case, two-stage annealing, that is, hydrogen annealing and PH ₃ annealing, is performed, and InP, InAlP, and InGaP are made to some extent by hydrogen annealing.
Alternatively, the contamination of the surface of InGaAsP is removed and the bonding state of impurities such as oxide and carbon is weak and unstable. Further, since the contamination of impurities whose surface bonding state is weakened by the PH ₃ annealing is removed, the interface level of the regrowth interface can be further reduced.

In the fourth surface treatment method for the regrown interface, it is preferable to perform phosphoric acid treatment on the regrown interface before performing hydrogen annealing. If the phosphoric acid treatment is performed on the regrowth interface before hydrogen annealing, the regrowth interface can be cleaned better. When this phosphoric acid treatment is performed, the regrowth interface can be cleaned and the interface state of the regrowth interface can be lowered by hydrogen annealing in a shorter time than when the phosphoric acid treatment is not performed.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a surface treatment method for a regrowth interface according to the present invention will be described below with reference to the drawings. It should be noted that these forms are merely examples in which a specific material is used and implementation is performed under specific conditions to the extent that the present invention can be understood. Therefore, the present invention is not limited only to these examples.

(First Embodiment) In the first embodiment, before starting the re-growth of the compound semiconductor on the AlGaAs substrate surface as the re-growth interface of the compound semiconductor, FIG.
Arsine (AsH ₃ ) annealing is performed in the sequence shown in FIG. The horizontal axis of the sequence in FIG. 1 represents time (arbitrary unit), and the vertical axis represents substrate temperature (° C.). Furthermore, FIG.
Shows the state of the timing of introduction of AsH ₃ gas, which is a raw material gas for regrowth, separately from the temperature.

First, the substrate temperature is changed from room temperature to 400 to 50.
The temperature is raised to a temperature in the range of 0 ° C., and AsH ₃ annealing is performed in an atmosphere containing only AsH ₃ gas for a predetermined time according to the raised temperature of the substrate. At this time AsH
The introduction of ₃ gas into the growth chamber is started before the temperature of the substrate reaches 400 ° C., and thereafter, the introduction of AsH ₃ gas is continued until the regrowth is completed. And in this case As
The pressure of AsH ₃ gas in the growth chamber during H ₃ annealing is set to about 5 × 10 ^{−4 to} 5 × 10 ⁻⁵ atm. This AsH
_{(3) By} annealing, the interface level of the regrown interface can be lowered.

After the completion of this AsH ₃ anneal, the substrate temperature is raised to a normal re-growth temperature in the range of 600 to 750 ° C., and the metal organic chemical vapor deposition (MOVPE) method is applied to the AlGaAs substrate surface. Re-grow AlGaAs.

The reason why the temperature range of the substrate during the AsH ₃ annealing is 400 to 500 ° C. is that hydrogen radicals are not sufficiently generated by the decomposition of AsH ₃ at a temperature of 400 ° C. or lower. Is sufficiently generated, and the oxide of Al is stabilized at a temperature of 500 ° C. or higher (see Document 1), so that the oxide can be easily removed. However, when removing oxides other than Al oxide and carbon, AsH ₃ annealing is performed to 50
It can be performed at a temperature of 0 ° C. or higher. It should be noted that the decomposition of AsH ₃ at a temperature of 500 ° C. or lower to generate a hydrogen radical is described in Reference 4: “Appl. Phys. Lett., 5
3 (9), 29 August 1988 ".

(Embodiment 2) In the second embodiment, hydrogen is formed on the surface of the AlGaAs substrate as the regrowth interface of the compound semiconductor by the sequence shown in FIG. 2 before the regrowth of the compound semiconductor is started. Annealing and AsH ₃ annealing are performed in this order. The horizontal axis of the sequence in FIG. 2 represents time (arbitrary unit), and the vertical axis represents substrate temperature (° C.). Further, FIG. 2 shows the state of the timing of introduction of AsH ₃ gas, which is a raw material gas for regrowth, separately from the temperature.

First, the substrate temperature is changed from room temperature to 200 to 43.
Raise to an appropriate temperature within the range of 0 ° C for about 30 minutes,
Hydrogen annealing is performed in an atmosphere of only hydrogen gas. In this case, the hydrogen gas pressure in the growth chamber during hydrogen annealing is set to about 0.1 to 1.0 atm (76 to 760 Torr). By this hydrogen annealing, the interface state at the regrowth interface can be reduced. The time for performing hydrogen annealing is preferably 10 minutes or more.

After completion of this hydrogen annealing, the temperature of the substrate is raised to an appropriate temperature within the range of 400 to 500 ° C.
For a predetermined time corresponding to the raised temperature of the substrate, A
AsH ₃ annealing is performed in an atmosphere containing only sH ₃ gas. At this time, the introduction of AsH ₃ gas into the growth chamber is started before the temperature of the substrate reaches 400 ° C., and thereafter, the introduction of AsH ₃ gas is continued until the regrowth is completed. In this case, A in the growth chamber during AsH ₃ annealing is used.
The pressure of the sH ₃ gas is about 5 × 10 ^{−4 to} 5 × 10 ⁻⁵ atm. By this AsH ₃ annealing, the interface level of the regrown interface can be lowered.

After the completion of this AsH ₃ anneal, the substrate temperature is raised to a normal re-growth temperature within the range of 600 to 750 ° C., and the metal oxide vapor phase epitaxy (MOVPE) method is applied to the AlGaAs substrate surface, for example. Re-grow AlGaAs.

Here, the reason why the lower limit of the temperature of the substrate during hydrogen annealing is set to 200 ° C. will be described with reference to FIG. FIG. 3A shows Auger electron spectroscopy (AE) of an AlGaAs substrate heat-treated in an ultrahigh vacuum.
S) A graph showing the analysis result. The horizontal axis of the graph is Al
The heating temperature (° C.) of the GaAs substrate is shown, and the vertical axis shows the relative intensity of each element on the substrate surface. The plots with white triangles in the graph represent the relative intensities of carbon (C), and the plots are almost connected by a broken line I ₁ . Also, the plots of white squares with crosses represent the relative intensities of aluminum (Al), and the plots are almost connected by a two-dot chain line I ₂ . The plots with black circles represent the relative intensities of gallium (Ga), and the plots are almost connected by the curve I ₃ . The white square plots represent the relative intensities of arsenic (As), and the plots are almost connected by the one-dot chain line I ₄ . Also, the plots with black triangles represent the relative intensity of oxygen (O).

From the AES spectrum analysis result, Al
The relative intensity of each element on the surface of the GaAs substrate was calculated by the following equation (1).

I _X = I _X ^* / (ΣI _m ^* ) (1) where _X in I _X is a code indicating each element, and I _X represents the relative intensity of each element, and ΣI _m ^* Is I _Ga ^* , I _Al ^* , I
_It represents a value obtained by converting the respective peak values of _As ^* , I _C ^* and I _O ^* . I _X ^* indicates the peak value of each element obtained by AES spectrum analysis.

As shown in the graph of FIG. 3 (A), the relative strength of carbon C on the surface of the substrate is lower at a heating temperature of around 200.degree. It is being removed. For example, the relative strength at a temperature lower than 200 ° C. is about 0.09, but the relative strength decreases from around 200 ° C. to around 300 ° C.
The relative strength near 0 ° C. has decreased to about 0.05.
The AES analysis results show that the heat treatment was performed in an ultrahigh vacuum, but even in a hydrogen atmosphere, if the heating temperature was 200 ° C. or higher, the carbon remaining on the surface of the substrate could be removed. It is thought to be possible.

The reason why the upper limit of the temperature of the substrate during hydrogen annealing is 430 ° C. is that the temperature above 430 ° C.
This is because As, which is a group V element, is desorbed from the surface of the substrate, and this desorption is suppressed.

The reason why the temperature range of the substrate during the AsH ₃ annealing is set to 400 to 500 ° C. is that hydrogen radicals are not sufficiently generated by decomposition of AsH ₃ at a temperature of 400 ° C. or lower. Is sufficiently generated, and the oxide of Al is stabilized at a temperature of 500 ° C. or higher (see Document 1), so that the oxide can be easily removed. However, when removing oxides other than Al oxide and carbon, AsH ₃ annealing is performed to 50
It can be performed at a temperature of 0 ° C. or higher.

(Third Embodiment) In the third embodiment, phosphoric acid treatment is performed on the regrown interface prior to hydrogen annealing.

First, phosphoric acid treatment is performed on the AlGaAs substrate. When performing phosphoric acid treatment, AlGaA
s The substrate is immersed in a phosphoric acid (H ₃ PO ₄ : 80 wt%) treatment solution in an inert gas atmosphere, for example, a nitrogen (N ₂ ) atmosphere. After the immersion, phosphoric acid remaining on the surface of the AlGaAs substrate is washed with ultrapure water (18 MΩcm).

Next, the substrate temperature is changed from room temperature to 200-43.
Raise it to an appropriate temperature within the range of 0 ° C for about 10 minutes,
Hydrogen annealing is performed in an atmosphere of only hydrogen gas. In this case, the hydrogen gas pressure in the growth chamber during hydrogen annealing is set to about 0.1 to 1.0 atm (76 to 760 Torr). By this hydrogen annealing, the interface state at the regrowth interface can be reduced.

After completion of this hydrogen annealing, the temperature of the substrate is raised to an appropriate temperature within the range of 400 to 500 ° C.
For a predetermined time corresponding to the raised temperature of the substrate, A
AsH ₃ annealing is performed in an atmosphere containing only sH ₃ gas. At this time, the introduction of AsH ₃ gas into the growth chamber is started before the temperature of the substrate reaches 400 ° C., and thereafter, the introduction of AsH ₃ gas is continued until the regrowth is completed. In this case, A in the growth chamber during AsH ₃ annealing is used.
The pressure of the sH ₃ gas is about 5 × 10 ^{−4 to} 5 × 10 ⁻⁵ atm. By this AsH ₃ annealing, the interface level of the regrown interface can be lowered.

After the completion of this AsH ₃ annealing, the temperature of the substrate is raised to a normal re-growth temperature within the range of 600 to 750 ° C., and the substrate surface of AlGaAs is subjected to metalorganic vapor phase epitaxy (MOVPE) method, for example, Re-grow AlGaAs.

Here, with reference to FIG. 3B, the reason why the lower limit of the temperature of the substrate during hydrogen annealing when the phosphoric acid treatment is performed is set to 200 ° C. will be described. FIG. 3B is a graph showing the AES analysis result of the AlGaAs substrate that was heat-treated in ultrahigh vacuum after the phosphoric acid treatment. The horizontal axis of the graph represents the heating temperature (° C.) of the AlGaAs substrate, and the vertical axis represents the relative intensity of each element on the substrate surface. The plots with white triangles in the graph represent the relative intensities of carbon (C), and the plots are almost connected by a broken line II ₁ .
Also, the plots of white squares with crosses represent the relative intensities of aluminum (Al), and each plot is a two-dot chain line II ₂
Is almost tied in. The plots with black circles represent the relative intensities of gallium (Ga), and the plots are almost connected by the curve II ₃ . The white square plot is arsenic (As).
Represents the relative intensity of each of the plots, and each plot is almost connected by a one-dot chain line II ₄ . Also, the plots with black triangles represent the relative intensity of oxygen (O).

As indicated by the chain double-dashed line II ₁ in the graph of FIG. 3B, the relative intensity of carbon (C) on the substrate surface is 200
At a heating temperature from around 0 ° C to a high temperature, the relative strength is lower than that at a temperature of less than 200 ° C to remove carbon. For example, the relative strength at a temperature lower than 200 ° C. is about 0.09, but the relative strength decreases from around 200 ° C. to around 300 ° C., and the relative strength near 300 ° C. is 0.05.
It has fallen to the extent. The AES analysis results show that the heat treatment was performed in an ultrahigh vacuum, but even in a hydrogen atmosphere, if the heating temperature was 200 ° C. or higher, the carbon remaining on the surface of the substrate could be removed. It is thought to be possible.

The reason why the upper limit of the temperature of the substrate during hydrogen annealing is 430 ° C. is that the temperature above 430 ° C.
This is because As, which is a group V element, is desorbed from the surface of the substrate, and this desorption is suppressed.

The reason why the temperature range of the substrate during the AsH ₃ annealing is set to 400 to 500 ° C. is that hydrogen radicals are not sufficiently generated by decomposition of AsH ₃ at a temperature of 400 ° C. or lower. Is sufficiently generated, and the oxide of Al is stabilized at a temperature of 500 ° C. or higher (see Document 1), so that the oxide can be easily removed. However, when removing oxides other than Al oxide and carbon, AsH ₃ annealing is performed to 50
It can be performed at a temperature of 0 ° C. or higher.

Here, FIG. 4B shows a spectrum diagram of the analysis result of the (011) surface of the AlGaAs substrate after the phosphoric acid treatment by Auger electron spectroscopy (AES) method. In addition, in FIG. 4A, for comparison before and after the phosphoric acid treatment, (01) of the AlGaAs substrate before the phosphoric acid treatment is performed.
1) The results of AES analysis of the surface are shown in a spectrum diagram. FIG.
The horizontal axes of (A) and (B) are the electron energy (e
V), and the vertical axis represents intensity (dN (E) / dE: differential logarithm). It should be noted that the spectrum peak values in the graphs of FIGS. 4A and 4B are merely schematic plots of typical peak values, and in fact, there are many other peak values than the typical peak values. A small peak value appears.

In the spectral diagrams of FIGS. 4A and 4B, LMM (Auger transition) transition Ga and As peaks and KLL (Auger transition) transition C, O and Al peaks are detected. That is, the electron energy is 3
Carbon (C) near 00 eV, oxygen (O) near 500 eV, gallium (Ga) near 1100 eV, 120
Arsenic (As) peaks are detected near 0 eV and aluminum (Al) peaks are detected near 1400 eV.

Comparing the spectral diagrams of (A) and (B) of FIG. 4, after the phosphoric acid treatment, the peak intensity of Ga was decreased as compared with that before the phosphoric acid treatment, while
The peak intensity of s is increasing. Therefore, it can be seen that the AlGaAs surface after the phosphoric acid treatment is As-rich. Therefore, by performing phosphoric acid treatment, Al
It is considered that the natural oxide film on the surface of the GaAs substrate has been removed and As simple substance is generated. A simple substance of As is 200-
If it is heated in the temperature range of 300 ° C., it evaporates, so that it can be easily removed. Therefore, by performing the phosphoric acid treatment, it can be expected that the contamination can be quickly removed during the hydrogen annealing.

(Confirmation of reduction of interface state) Next, hydrogen annealing is performed using the surface quantum well structure made of the compound semiconductor shown in FIG. 5 as a sample structure to reduce the interface state of the regrown interface. I will explain what I did. FIG.
[Fig. 3] is a cross-sectional structure diagram of a sample structure. It is not clear at present what kind of reaction occurs on the regrown surface by performing hydrogen annealing. However, as described below,
Considering that the sample structure, which did not emit PL light because the interface state density did not sufficiently decrease in the normal heat purification treatment, emitted PL light when hydrogen annealing was performed, it was confirmed that hydrogen annealing resulted in oxide formation on the AlGaAs surface. It is considered that carbon and carbon have been removed to reveal a clean surface.

As shown in FIG. 5, this sample structure has a thickness of 8300 on the (001) plane of the semi-insulating GaAs substrate 10.
Å GaAs buffer layer 12, AlGaAs third barrier layer 14, thickness 140 Å second quantum well layer 16, AlGa
Second barrier layer 18 of As, first quantum well layer 2 having a thickness of 70Å
The first barrier layer 22 of 0 and AlGaAs is sequentially laminated. However, the first to third barrier layers are made of Al ₂₈ Ga ₇₂ As.
Consists of The first barrier layer has a surface barrier layer 24 having a thickness of 70Å and a surface of the surface barrier layer as a regrown interface 26 and a thickness of 430Å regrown on the regrown interface 26.
Regrowth layer 28 of

When the surface quantum well structure is irradiated with laser light, PL (photoluminescence) light is emitted from the first quantum well layer (hereinafter also referred to as the surface quantum well layer or QW1) 20 and the second quantum well layer 16. Occurs in.

When this sample structure was manufactured by performing only conventional heat cleaning treatment without hydrogen annealing, PL emission did not occur even when irradiated with laser light.
This indicates that the reduction of the interface state of the regrowth interface is insufficient only by the heat cleaning treatment.

First, with reference to FIG. 6, the relationship between the time for performing hydrogen annealing and the effect of lowering the interface state will be described.

In FIG. 6A, when the phosphoric acid treatment is not performed, the hydrogen annealing time is fixed to 10 minutes,
The measurement results of the effect of lowering the interface state depending on the temperature of hydrogen annealing are shown. FIG. 6A is a graph showing the relationship between the laser light intensity incident on the sample structure and the normalized PL emission intensity when the temperature of hydrogen annealing is used as a parameter. The horizontal axis of the graph of FIG. 6A represents the laser light intensity (W) in logarithmic display, and the vertical axis represents the normalized PL emission intensity in logarithmic display. In the graph of FIG. 6A, the black triangle plots indicate the hydrogen anneal at 250 ° C., the white square plots indicate the hydrogen anneal at 300 ° C., and the black circle plots indicate the hydrogen anneal. Anneal 38
The results of the measurements performed at 0 ° C. are shown. When the annealing temperature is 400 ° C. or higher, group V atoms are desorbed from the regrowth interface (As escape).
The above measurement was not performed.

The normalized PL emission intensity is represented by the following equation (2). I _N = I _{QW (70)} / I _{QW (140)} (2) where I _N is the normalized PL emission intensity, I _{QW (70)} is the PL emission intensity of QW1 with a thickness of 70Å, and , _{IQW (140)}
Represents the PL emission intensity of QW2 having a thickness of 140Å.

As shown in the graph of FIG. 6 (A), the higher the temperature during hydrogen annealing, the higher the P with respect to the laser light intensity.
The L emission intensity is high. Therefore, it has been confirmed that the interface state can be lowered as the hydrogen annealing is performed at a temperature as high as possible within the range where the desorption of the group V atom does not occur.

Next, as shown in FIG. 6B, after the phosphoric acid treatment, the time of hydrogen annealing is fixed to 10 minutes, and the measurement result of the effect of lowering the interface state due to the temperature of hydrogen annealing is shown. Indicates. FIG. 6B is a graph showing the relationship between the laser light intensity incident on the sample structure and the normalized PL emission intensity when the temperature of hydrogen annealing is used as a parameter. The horizontal axis of the graph (B) of FIG. 6 represents the laser light intensity (W) in logarithmic display, and the vertical axis represents the normalized PL emission intensity in logarithmic display. In the graph of FIG. 6B, the plots with black triangles indicate that hydrogen annealing was performed at 250 ° C., the plots with open squares indicate hydrogen annealing at 300 ° C., the plots with black circles indicate hydrogen. Anneal 38
The results of the measurements performed at 0 ° C. are shown.

As shown in the graph of FIG. 6B, even when the phosphoric acid treatment is performed, the PL emission intensity with respect to the laser beam intensity increases as the temperature during hydrogen annealing increases. Further, comparing the graphs of (A) and (B) of FIG. 6, when the temperature at which the hydrogen annealing is performed is 300 ° C. or higher, the PL light emission intensity with respect to the laser light intensity is the same regardless of the phosphoric acid treatment. It will be about. However, FIG. 6 (B)
When the phosphoric acid treatment shown in FIG. 6 is performed, the slope of the distribution of the same type of plot is gentler than when the phosphoric acid treatment shown in FIG. 6 (A) is not performed. Therefore, it is understood that the interface state can be further lowered when the phosphoric acid treatment is performed.

Next, with reference to FIG. 7, the relationship between the hydrogen annealing time and the effect of lowering the interface state will be described.

In FIG. 7, the hydrogen annealing temperature is set to 300.
The measurement result of the effect of lowering the interface state with the time of hydrogen annealing is shown by fixing at ℃. FIG. 7 is a graph showing the relationship between the laser light intensity incident on the sample structure and the normalized PL emission intensity when the hydrogen annealing time is used as a parameter. The horizontal axis of the graph in FIG. 7 represents the laser light intensity (W) in logarithmic display, and the vertical axis represents the normalized PL emission intensity in logarithmic display. The black square plot in the graph of FIG. 7 indicates that after the phosphoric acid treatment, hydrogen anneal is performed.
The plots marked with black triangles indicate that hydrogen annealing was performed for 30 minutes without phosphoric acid treatment, and the plots marked with open squares indicate that hydrogen annealing was performed for 10 minutes after phosphoric acid treatment. The plots with white triangles represent the measurement results when hydrogen annealing was performed for 10 minutes without phosphoric acid treatment.

Comparing the plots of the black triangles and the plots of the white triangles in the graph of FIG. 7 with each other, when the phosphoric acid treatment is not performed, the longer the hydrogen annealing time is, the more the PL emission intensity with respect to the laser light intensity. Is getting bigger. Therefore,
When the phosphoric acid treatment is not performed, the longer the hydrogen annealing time is, the lower the interface state can be reduced.

Further, comparing the plots of the black triangles and the plots of the white squares in the graph of FIG. 7, when the phosphoric acid treatment was performed, hydrogen annealing was performed for 10 minutes, and when the phosphoric acid treatment was not performed, it was 30. It almost overlaps with the plot when hydrogen annealing for 1 minute is performed. Especially, in the region where the laser intensity is low, P
The L emission intensity is high. Therefore, when the phosphoric acid treatment is performed, the interface state can be sufficiently lowered in a short time of about 10 minutes.

However, as shown by the black square plot in the graph of FIG. 7, when the phosphoric acid treatment is performed, hydrogen annealing is performed for 30 minutes, as compared with the case where hydrogen annealing is performed for 10 minutes. The PL emission intensity with respect to the intensity is reduced. Therefore, when phosphoric acid treatment is performed,
The time for performing hydrogen annealing is preferably about 10 minutes or less.

(Embodiment 4) Next, with reference to FIG. 8, an example in which the surface treatment method of the regrowth interface of the present invention is used for manufacturing a semiconductor laser will be described.

Both (A) and (B) of FIG.
FIG. 3 is a vertical cross-sectional view of the embedded laser diode structure taken along a plane perpendicular to the light emission direction.

First, the laser diode (hereinafter, also referred to as LD) shown in FIG. 8A will be described. This L
D denotes an n-AlGaAs lower cladding layer 32, an active layer 34 and a p-AlGaAs on an n-GaAs substrate 30.
s upper cladding layer 36 is sequentially laminated. Then, the upper clad layer 36, the active layer 34, and the lower clad layer 32 are etched to form a mesa shape. Then, the side surface of this mesa shape becomes the first regrowth interface 38. Then, as current blocking layers, a lower current blocking layer 40 of p-AlGaAs and an upper current blocking layer 42 of n-AlGaAs are sequentially grown on both sides of the mesa shape. The upper surface of the upper current blocking layer 42 and the top portion of the mesa shape serve as the second regrowth interface 44. Then, on the second regrowth interface 44, pAlGa
A clad layer 46 of As and a cap layer 48 of p-GaAs are sequentially grown. Then, the first and second regrowth interfaces 38 and 44 are subjected to the same surface treatment as the method of any one of the first to third embodiments described above.

Next, the LD shown in FIG. 8B will be described. This LD has an n-type on an n-GaAs substrate 50.
AlGaAs lower clad layer 52, active layer 54, p-
AlGaAs upper cladding layer 56 and p-GaAs
The first cap layer 68a is sequentially laminated. Then, the upper clad layer 56, the active layer 54 and the lower clad layer 52 are etched to form a mesa shape. Then, the side surface of this mesa shape becomes the first regrowth interface 58. Then, as current blocking layers, a lower current blocking layer 60 of p-AlGaAs and an upper current blocking layer 62 of n-AlGaAs are sequentially grown on both sides of the mesa shape. The upper surface of the upper current blocking layer 62 and the top portion of the mesa shape serve as the second regrowth interface 64. Then, on the second regrowth interface 64, pAlGa
A clad layer 66 of As and a cap layer 68b of p-GaAs are sequentially grown. Then, the first and second regrowth interfaces 58 and 64 are subjected to the same surface treatment as the method of any one of the first to third embodiments described above.

Next, FIG. 8C shows a longitudinal sectional view of the ridge-embedded laser diode structure taken along a plane perpendicular to the light emission direction.

The LD shown in FIG. 8C is n-GaAs.
On the substrate 70, the lower cladding layer 7 of n-AlGaAs
2, active layer 74, upper cladding layer 7 of p-AlGaAs
6 and a first cap layer 88a of p-GaAs are sequentially laminated. Then, the first cap layer 88a and the upper clad layer 76 are etched to form a mesa shape in which a specific low index surface appears. Then, the side surface of this mesa shape becomes the first regrowth interface 78. Then, on both sides of the mesa shape, a lower current blocking layer 80 of n-AlGaAs and an upper current blocking layer 82 of n-GaAs are sequentially grown as current blocking layers. The upper surface of the upper current blocking layer 82 and the top portion of the mesa shape are
It becomes the second regrowth interface 84. Then, a second cap layer 88b of p-GaAs is sequentially grown on the second regrowth interface 84. Further, in this structure, the surface after the burying can be flattened, so that the electrodes can be easily formed. Then, the first and second regrowth interfaces 38 and 44 are subjected to the same surface treatment as the method of any one of the first to third embodiments described above.

In each of the LDs shown in FIGS. 8A to 8C, the active layer is, for example, GaAs /
InGaAs / GaAs single quantum well structure or Ga
A double quantum well structure of As / InGaAs / GaAs can be used.

In the LD shown in FIGS. 8A to 8C, the interface state is lowered by performing the surface treatment on the first and second regrown interfaces. As a result, it is possible to suppress the current leaking the interface state at the first regrowth interface in the vicinity of the active layer. In addition, carrier traps due to interface levels at the second regrowth interface at the top of the ridge on the active layer can be reduced. Therefore, effects such as reduction of the threshold current of the laser and improvement of the light emission efficiency can be expected.

(Fifth Embodiment) Next, referring to FIG.
An example in which the surface treatment method of the regrowth interface of the present invention is used for manufacturing the window structure of the end face of the semiconductor laser will be described.

FIG. 9A is a perspective view of a 0.98 μm laser diode for pumping a fiber amplifier (hereinafter, also referred to as an LD) which requires a high light output operation.

On the n-GaAs substrate 90, n-AlG is formed.
The lower clad layer 92 of aAs, the active layer 94, and the upper clad layer 96 of ridge-shaped p-AlGaAs are sequentially laminated. A p-GaAs cap layer 98 is provided on the ridge-shaped top of the upper clad layer 96. Further, both sides of the ridge shape are covered with an insulating film 100 of SiO ₂ . A p-side electrode 102 is provided on the cap layer 98 and the insulating film 100, while an n-side electrode 104 is provided on the lower surface of the substrate 90.

By the way, this LD has a problem that a sudden accident occurs during high light output operation of 100 W or more. The cause of the sudden failure is deterioration of the element end face. In the high light output state, defects on the end surface 108 of the LD body 106 increase. When the number of defects increases, the end face 108 melts due to heat generated by re-absorption of self-emitted light (optical damage). A solution for suppressing or removing the deterioration of the end face is to reduce the non-radiative recombination rate by lowering the interface state of the end face 108, thereby suppressing heat generation. Then, as a method of increasing the bandgap of the end face 108 as compared with the bandgap of the LD body 106 in order to suppress light absorption at the end face, it is conceivable to provide a window structure on the end face.

Here, FIG. 9B shows an example of the window structure. 9B is a side view of the laser diode shown in FIG. 9A viewed from a direction perpendicular to the light emission direction. 9 (B) shows a window structure 110 not shown in FIG. 9 (A).

This window structure 110 is made of, for example, Al having a larger Al composition than the AlGaAs composition of the cladding layer.
Re-grow GaAs. At the time of this regrowth, by using the surface treatment method of the present invention, the interface level of the end face as the regrowth interface can be reduced. As a result, the COD level is improved, and the occurrence of catastrophic failure can be suppressed more effectively.

The window structure may be provided on the end face of the LD shown in FIGS. 8A to 8C.

In each of the above-described embodiments, only examples in which these inventions are configured under specific conditions have been described, but many modifications and variations can be made to these inventions. For example, in the above-described embodiment, the surface of AlGaAs is mainly used as the regrowth interface, but in the present invention, the regrowth interface is not limited to this. For example, in the present invention, AlAs and Ga are used as the regrown interfaces.
As, InAlAs, InGaAs, InP, InAl
The surface of a compound semiconductor such as P, InGaP or InGaAsP can be used. However, as the regrowth interface, InP, InAlP, InGaP or InG
When the surface of aAsP is used, phosphine (PH ₃ ) annealing is performed under optimized temperature conditions instead of AH ₃ annealing.

[0082]

According to the first surface treatment method of the regrowth interface according to the present application, AlAs, GaAs, AlGaAs, InAlAs as the regrowth interface of the compound semiconductor is obtained.
Alternatively, AH ₃ annealing is performed on the surface of InGaAs, and according to the third surface treatment method of the regrowth interface according to this application, InP, InAlP, InGaP or I
PH ₃ annealing is performed on the surface of nGaAsP. A
The H ₃ anneal or PH ₃ anneal can remove the contamination of the regrowth interface and lower the interface level of the regrowth interface.

According to the second surface treatment method for the regrown interface according to the present application, AlAs, GaAs, AlGaAs, InAlA as the regrown interface of the compound semiconductor are used.
Hydrogen annealing and AH ₃ annealing are performed in this order on the surface of s or InGaAs, and according to the fourth surface treatment method of the regrown interface according to this application, InP, I
Hydrogen annealing and PH ₃ annealing are performed in this order on the surface of nAlP, InGaP or InGaAsP. After the contamination of the regrowth interface is removed to some extent by the hydrogen anneal, the contamination of the regrowth interface is further removed by the AH ₃ anneal or PH ₃ anneal, so that the interface level of the regrowth interface can be further lowered.

In the second and fourth surface treatment methods for the regrown interface according to this application, if the phosphoric acid treatment is applied to the regrown interface before hydrogen annealing, the regrown interface is cleaned more. Can be converted. In this case, the regrown interface can be cleaned by hydrogen annealing for a shorter time than in the case where the phosphoric acid treatment is not performed.

[Brief description of drawings]

FIG. 1 is a diagram showing a surface treatment sequence of a regrown interface of an AlGaAs substrate in the first embodiment.

FIG. 2 is a diagram showing a surface treatment sequence of a regrown interface of an AlGaAs substrate in the second embodiment.

FIG. 3A shows AlG heat-treated in an ultrahigh vacuum.
It is a graph which shows the Auger electron spectroscopy (AES) analysis result of an aAs substrate, (B) is a graph which shows the AES analysis result of the AlGaAs substrate heat-processed in ultrahigh vacuum after performing phosphoric acid processing.

FIG. 4A is AlGaAs before phosphoric acid treatment.
It is a spectrum figure which shows the AES analysis result of the (011) surface of a board | substrate, (B) is AlG after performing a phosphoric acid process.
It is a spectrum figure which shows the AES analysis result of the (011) surface of an aAs substrate.

FIG. 5 is a cross-sectional structure diagram of a sample structure.

FIG. 6 shows the intensity of laser light incident on a sample structure and the normalized P when the temperature of hydrogen annealing is used as a parameter.
It is a graph which shows the relationship with L luminescence intensity, (A) is a graph when phosphoric acid processing is not performed, (B) is a graph when phosphoric acid processing is performed.

FIG. 7 shows the intensity of laser light incident on the sample structure and the normalized P when the time of hydrogen annealing is used as a parameter.
It is a graph which shows the relationship with L light emission intensity.

8A and 8B are vertical sectional views of the embedded laser diode, and FIG. 8C is a vertical sectional view of the ridge embedded laser diode.

FIG. 9A is a perspective view of a laser diode,
(B) is a side view of the laser diode.

[Explanation of symbols]

 10: Substrate 12: Buffer layer 14: Third barrier layer 16: Second quantum well layer (QW2) 18: Second barrier layer 20: First quantum well layer, surface quantum well layer (QW1) 22: First barrier layer 24: Surface barrier layer 26: Regrowth layer 30, 50, 70, 90: Substrate 32, 52, 72, 92: Lower clad layer 34, 54, 74, 94: Active layer 36, 56, 76, 96: Upper side Cladding layers 38, 58, 78: first regrowth interface 40, 60, 80: lower current blocking layer 42, 62, 82: upper current blocking layer 44, 64, 84: second regrowth interface 46: cladding layer 68a , 88a: first cap layer 68b, 88b: second cap layer 98: cap layer 100: insulating film 102: p-side electrode 104: n-side electrode 106: LD body 108: end face 110: window structure

Claims (6)

[Claims] 1. A as a regrowth interface of a compound semiconductor
A method for surface treatment of a regrowth interface, characterized by performing arsine (AsH ₃ ) annealing on the surface of 1As, GaAs, AlGaAs, InAlAs or InGaAs before starting the regrowth of the compound semiconductor. 2. A as a regrowth interface of a compound semiconductor
For the surface of 1As, GaAs, AlGaAs, InAlAs or InGaAs, hydrogen annealing and arsine (As
H ₃ ) A surface treatment method for a regrowth interface, characterized by performing annealing in this order. 3. The surface of the regrown interface according to claim 2, wherein phosphoric acid treatment is performed on the regrown interface before the hydrogen annealing. Processing method. 4. I as a regrowth interface of a compound semiconductor
A method for surface treatment of a regrowth interface, which comprises performing phosphine (PH ₃ ) annealing on the surface of nP, InAlP, InGaP or InGaAsP before starting the regrowth of the compound semiconductor. 5. I as a regrowth interface of a compound semiconductor
Surface treatment of regrowth interface characterized by performing hydrogen annealing and phosphine (PH ₃ ) annealing in this order on the surface of nP, InAlP, InGaP or InGaAsP before starting the regrowth of the compound semiconductor. Method. 6. The surface treatment method for a regrown interface according to claim 5, wherein phosphoric acid treatment is performed on the regrown interface before the hydrogen annealing. Processing method.