JP3435083B2 - Semiconductor thin film regrowth method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regrowth of a III-V compound semiconductor thin film, and more particularly to a method for regrowth of a III-V compound semiconductor thin film used for manufacturing an optical device or an electronic device. Thus, for example, it relates to a method for forming a semiconductor electrode layer for non-alloy.

[0002]

2. Description of the Related Art III-V compound semiconductors are widely used in electronic devices and optical devices. These devices are formed by laminating the same kind of III-V compound semiconductor material on a III-V compound semiconductor substrate using a thin film forming apparatus. Then, a highly-doped compound semiconductor layer is formed on the outermost surface of the device structure to improve contact with the metal electrode. The method of forming the III-V compound semiconductor thin film is roughly divided into two flows. One of them is a method of forming a thin film in vacuum, which is a molecular beam epitaxy method (MBE), a chemical beam epitaxy method (CBE), a gas source molecular beam epitaxy method (GSM).
BE) and the like. The other flow is a method of forming a thin film in a hydrogen atmosphere of 0.1 to 1 atm, and a typical example is metalorganic pyrolysis (MOCVD). The MOCVD method is most widely used for practical device fabrication. Most optical devices utilize the rectifying properties of pn junctions. FIG. 1A shows a cross section of a thin film structure for an optical device using an InP substrate. The procedure for producing an optical device using the MOCVD method is as follows. After forming the n-type InP buffer layer 2 and then the active layer 3 on the n-type InP substrate 1, the p-type InP layer 4 is laminated, and the electrode contact layer 5 in which the p-type dopant is highly doped, Further, the InP cap layer 6 is formed. The InP cap layer 6 is used to protect the electrode contact layer 5 from various processes such as lithography and insulating film formation. Finally, the InP cap layer 6 is removed, and the metal electrode 7 is vapor-deposited [see FIG. 1 (b)]. At this time, the p-type dopant is Zn and the composition of the electrode layer is InG.
aAs is each the most common. The maximum value of the doping amount is determined by the solubility and is about 1 × 10 ¹⁹ / cm ³ . p
Type electrode contact layer 5 highly doped with a type dopant
Then, when the metal electrode 7 is brought into contact with the metal electrode 7, a Schottky barrier is formed at the interface between them. Since this barrier has a rectifying property, a larger voltage is required when a current is passed through the element, resulting in an increase in power consumption. The height of this barrier sharply decreases as the doping amount of the electrode layer increases. for that reason,
Carbon has attracted attention as a p-type dopant that can be highly doped. The maximum carrier concentration of the obtained InGaAs depends on the film forming method. That is, MOCV
It is about 3 × 10 ¹⁹ / cm ^{3 in} the D method, and about 1 × 10 ²⁰ / cm ³ in the MBE and CBE. Now, in order to improve the performance of the device, a so-called hybrid method, which is a method of manufacturing a device by utilizing respective features of different thin film growth methods, is drawing attention. For example, as shown in FIG.
The structure (a) is formed, taken out from the thin film growth furnace, and then the electrode layer doped with a very high concentration is regrown by the MBE or CBE method. Figure 1
As shown in (c), on the above InGaAs film 5,
The carbon-doped InGaAs film 8 is regrown. However, the success of this hybrid method depends on how impurities (mainly oxides) at the regrowth interface are removed. In recent years, a method using a reactive gas has attracted attention as a cleaning means in a vacuum container. With respect to GaAs, chlorine gas, AsCl _{3 and the} like are effective for removing the oxide film, but there is a risk of etching even inside the film, and there is a risk of corroding the vacuum container when used for a long period of time. Although hydrogen radicals are also effective and highly reactive with AlGaAs, they require an ECR (electron cyclotron resonance) plasma source for generating hydrogen radicals and a vacuum container separate from the thin film growth chamber. Trisdimethylaminoarsine (TDMAAs) can remove GaAs oxide film, but it has been reported to have an action of etching GaAs at high temperature (Journal of Crystal Grouse, 175/176, 1997, p. 38).
7-392). However, there was no example applied to InGaAs. As described above, in the prior art, InGaA
There was no effective means for cleaning s in a vacuum vessel and smoothing its surface.

[0003]

The natural oxide film formed on InGaAs is mainly composed of two types. That is, GaA
s is an oxide of Ga ₂ O ₃ and an oxide of InP an In
₂ O ₃ . The simplest method for removing these is evaporation removal by heating at high temperature. According to the observation of RHHED (electron diffractometer) and Auger analysis, when heated in an As atmosphere, Ga ₂ O ₃ is 580 to 600 ° C. and In ₂ O ₃ is 5 ° C.
Evaporate at 25 ° C. However, with these analytical methods, 1%
Due to the inability to detect the following residues and the presence of hydrocarbons on the surface, a much higher temperature is required to obtain a device quality clean interface. As a result, since the oxide film is heated to a high temperature of 600 ° C. or higher, the oxide film is evaporated and removed, but there is a problem that the group V element is severely detached from the surface and the surface is roughened. The hybrid method has another problem. As shown in FIG. 1, since the device structure undergoes various processes (lithography, insulating film formation, etc.),
An InP cap is provided. This is wet-etched before regrowth, and a hydrochloric acid / phosphoric acid mixed solution is used as the etching solution. The reason is that this mixture has a high InP etching rate and a low InGaAs etching rate. However, since the etching rate of InGaAs is not zero and has selectivity,
The composition of the wet-etched extreme surface of InGaAs is altered. In other words, InGaAs before wet etching is I
It has the same lattice constant as nP, but since phosphoric acid etches GaAs, the lattice constant of the wet-etched InGaAs pole surface is different from that of InP. Therefore, I that is lattice-matched to InP on the surface from which the oxide film is removed
When a film of nGaAs composition is regrown, strain is accumulated at the interface, and eventually defects are generated in the regrown film. Thus, even if a clean surface is obtained, there is a big problem that the crystallinity of the regrown film deteriorates.

An object of the present invention is to eliminate the above-mentioned problems in the prior art, namely, In formed on a substrate.
When a second semiconductor layer made of a III-V group compound semiconductor lattice-matched with the first semiconductor layer is regrown on the first semiconductor layer made of GaAs or InGaAsP, the device fabrication process is convenient. The surface oxide film formed on the first semiconductor layer by being exposed to air is treated with trisdimethylaminoarsine (TDMAAs),
By removing it by heating in a specific atmosphere containing phosphorus (P molecules) to form a clean and flat surface and forming a semiconductor layer that relaxes lattice strain, strain does not accumulate at the growth interface and It is an object of the present invention to provide a method capable of re-growing a III-V group compound semiconductor film having good crystallinity with few defects in the grown film.

[0005]

In order to achieve the above object, the present invention has a structure as described in the claims. That is, in a thin film growth method for growing a III-V group compound semiconductor in a vacuum chamber as set forth in claim 1, the first semiconductor layer and a lattice are formed on the first semiconductor layer made of InGaAs or InGaAsP. A method of regrowth of a matching III-V group compound semiconductor second semiconductor layer, wherein the first semiconductor layer is trisdimethylaminoarsine before regrowth of the second semiconductor layer. A semiconductor thin film including a step of heating in a mixed atmosphere containing phosphorus to remove a surface oxide film for cleaning and to form a semiconductor layer having a composition for relaxing lattice strain on the outermost surface of the first semiconductor layer. This is a regrowth method. Further, as described in claim 2, in the method of claim 1, the heating temperature in the mixed atmosphere containing trisdimethylaminoarsine and phosphorus is in the range of 515 to 540 ° C. is there. Further, as described in claim 3, in the method for regrowth of a semiconductor thin film according to claim 1 or 2, heating in a mixed atmosphere containing trisdimethylaminoarsine and phosphorus is performed to form the first semiconductor layer. A method of regrowing a semiconductor thin film, comprising a step of removing a surface oxide film and forming a semiconductor layer having a composition for relaxing lattice strain, and subsequently, regrowing p-type InGaAs heavily doped with carbon. To do. Also, as described in claim 4, formed on a substrate InGaA
A method of re-growing a second semiconductor layer made of a III-V group compound semiconductor lattice-matched with the first semiconductor layer on the first semiconductor layer made of s or InGaAsP. A step of heating the first semiconductor layer in an atmosphere containing trisdimethylaminoarsine to remove the surface oxide film before regrowth of the layer; and then heating to a high temperature in an atmosphere containing phosphorus, A step of forming a thin film layer made of InGaAsP on the outermost surface of the first semiconductor layer to relax lattice distortion, and a second semiconductor layer made of a III-V group compound semiconductor is regrown on the thin film layer made of InGaAsP. A method of regrowing a semiconductor thin film including the step of In addition, as described in claim 5 ,
4 , the heating temperature in the atmosphere of trisdimethylaminoarsine is in the range of 515 to 540 ° C. The semiconductor thin film regrowth method. Further, as described in claim 6 , in the semiconductor thin film regrowth method according to claim 4 or 5 , a III-V group compound semiconductor which is regenerated and grown on a thin film layer made of InGaAsP for relaxing lattice distortion. The second semiconductor layer made of is a semiconductor thin film regrowth method for forming a non-alloy semiconductor electrode layer made of p-type InGaAs doped with carbon at a high concentration.

The semiconductor thin film regrowth method of the present invention is a first method.
In addition, even if the semiconductor layer is made of InGaAs or InGaAsP having a very thick oxide film exposed to air for a long period of time, the oxide film can be easily removed and cleaned in a vacuum container. In order to simultaneously achieve the two goals of bringing the composition of the surface of the semiconductor layer closer to InP lattice matching in (2), as described in (1), (2), (3), in a mixed atmosphere containing TDMAAs and phosphorus. InG
The heat treatment is performed on the aAs or InGaAsP semiconductor layer. When heated InGaAs is irradiated with TDMAAs, TDMAAs are decomposed on the surface and the generated hydrogen radicals react with the InGaAs oxide film. Since the hydrogen radical reacts only with the outermost layer, the thickness of the oxide film is 2 to
If it is a 3 atomic layer, it will be removed in about 5 minutes. As the air exposure time becomes longer, the thickness of the oxide film also increases, and the oxide film itself is transformed into a strong one. As a result, the heating time of InGaAs becomes very long, and the heating temperature must be high. In order to solve this, the hydrogen radical is reacted with another molecule to make this molecule a radical,
It is necessary to enhance the chemical action by radicals, that is, the reduction reaction. Specifically, if TDMAAs and another gas are mixed and irradiated on the InGaAs surface, the hydrogen radicals and the gas molecules may interact with each other, and the gas molecules may be radicalized, while migrating on the surface. There is. As a result of various experiments, the present inventors have found that TDMA
It was found that the reduction reaction was strengthened when the molecular beams of As and phosphorus were simultaneously irradiated. After the oxide is removed and cleaned, InGaAsP is formed on the surface of the semiconductor layer because it is heated in the phosphorus atmosphere. By re-growing InGaAs under the lattice matching condition on such a surface, InGaAs having good crystallinity can be obtained. In addition, the semiconductor thin film regrowth method of the present invention achieves the goal of cleaning InGaAs or InGaAsP exposed to air for a relatively short period of time in a vacuum chamber and bringing the surface composition close to InP lattice matching. We propose two methods. One is heating InGaAs in a phosphorus atmosphere, the other is TDMAAs.
It is characterized by heating in an atmosphere. That is, as described in (1) claims 4 , 5, and 6 ,
At the same time as cleaning by high temperature heating (570 ° C. or higher and less than 600 ° C.) in a phosphorus atmosphere, a thin film layer made of InGaAsP that relaxes the lattice strain is formed, so that strain does not accumulate at the interface and few defects occur. There is an effect that a semiconductor film having crystallinity can be manufactured with high yield. It should be noted that if the heating temperature in the phosphorus atmosphere is 600 ° C. or higher, the group V element is severely detached from the surface and the surface becomes rough, which is not preferable. As described above [FIGS. 1A to 1C], In after the InP cap layer is wet-etched, In
The composition of the extreme surface of GaAs is In0.53Ga0.47A.
It deviates from s and becomes In rich. That is, the surface layer is I
It is larger than the lattice constant of nP. Therefore, if heating is performed in a phosphorus (P molecule) atmosphere, As on the surface replaces P and I
A single atomic layer or several atomic layers of nGaAsP are formed. Since the composition of In and Ga does not change during heating, this I-compared to the lattice constant of the In-rich InGaAs pole surface
The lattice constant of the nGaAsP surface layer is small, that is,
It approaches the lattice constant of InP. By regrowth of InGaAs under the lattice matching condition on the surface of such a quaternary composition, there is an effect that regrowth of InGaAs having good crystallinity can be performed with good yield without generating defects.
(2) As described in claims 4 , 5 , and 6 , TDMAA
The oxide film is removed by heating in an atmosphere containing s (trisdimethylaminoarsine) (515 to 540 ° C.) to form a flat and clean surface, and the lattice strain is relaxed by heating at high temperature in a phosphorus atmosphere. There is an effect that a thin film layer made of InGaAsP is formed, and a semiconductor film having good crystallinity without strain accumulation at the interface and with good yield can be manufactured with high yield. The above document (Journal of Crystal Grouse, 175/176, 1997)
Years, pp. 387-392).
Is thermally decomposed at 450 ° C. to generate various radicals and As. Hydrogen radicals and methyl radicals are considered as the radicals. Methane is used for RIE etching of GaAs.
This is because it combines with a group element to form a compound having a high vapor pressure. On the other hand, hydrogen radicals have the action of removing the oxide film, but they are not as reactive as etching. Therefore,
Irradiating heated InGaAs with TDMAAs,
TDMAAs are decomposed on the surface, and the generated hydrogen radicals and methyl radicals react with InGaAs. The temperature at which InGaAs (P) is grown by CBE or MBE is about 500 to 515 ° C. This temperature is TD
It thermally decomposes MAAs, but not at a temperature high enough to etch methyl radicals. Therefore, it is considered that when the optimum temperature is selected, only the action of removing the oxide film by hydrogen radicals occurs, and the etching action by methyl radicals is negligible. Moreover, since it is a radical reaction, the cleaning temperature can be considerably lowered to a range of about 515 to 540 ° C. as compared with evaporation removal. After cleaning with TDMAAs, as described in (1) above, by heating in a phosphorus atmosphere, I
A thin film layer of nGaAsP is formed. On such a surface,
By regrowing InGaAs or the like under the lattice matching condition, there is an effect that an InGaAs layer having good crystallinity can be obtained with high yield. The semiconductor thin film regrowth method of the present invention solves the problems of low-temperature removal of surface oxide film and lattice distortion in the conventional semiconductor thin film regrowth, and heating in a trisdimethylaminoarsine (TDMAAs) atmosphere. Can be solved by removing the oxide film by means of, and then heating in a phosphorus (P molecule) atmosphere to form InGaAsP on the outermost surface. That is, when the InP cap layer is wet-etched and InGaAs is exposed to the air, a natural oxide film is formed. InGaA heated TDMAAs
When s is irradiated, TDMAAs are decomposed on the surface, the generated hydrogen radicals react with InGaAs, and the surface oxide film of InGaAs can be removed at a heating temperature of, for example, 515 ° C. or higher. However, this method is effective when the air exposure time is, for example, one day or less, but when it is longer than that, it becomes difficult to remove the surface oxide film. this is,
If the exposure time is within 1 day, the thickness of the surface oxide film is 2 to
This is because it is a triatomic layer, but the thickness of the oxide film increases as the exposure time increases. Since various processes (lithography, insulating film formation, etc.) are performed when manufacturing an actual device, the air exposure time may extend to several days or longer. Even in the case of such a long-term exposure, heating in a mixed atmosphere containing trisdimethylaminoarsine (TDMAAs) and phosphorus (P molecule) according to claims 1 to 3 of the present invention effectively It is possible to remove the surface oxide film and form a semiconductor layer that relaxes the lattice strain.
This is an effective semiconductor thin film regrowth method applicable to an actual device process.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in more detail. <Embodiment 1> In the present embodiment, the relationship between the removal of the oxide film and the heating atmosphere was investigated. Using an MOCVD method, an n-type InP buffer layer (thickness 0.4 μm) and Zn 10 ¹⁸ / cm ³ -doped I were formed on the n-type InP substrate I.
An nGaAs layer was grown to 3000 Å and finally an InP cap layer was grown in that order. This was taken out in the air, and the InP cap layer was wet-etched using a mixed solution of hydrochloric acid and phosphoric acid.
This sample was divided into two and left in the air for one week. CBE was used for the thin film growth method of regrowth. After degreasing the above sample, it was washed with water and loaded into a CBE apparatus. To clean the sample surface (1) Approximately 51 in TDMAAs atmosphere
Heat at 5 ° C for 5 minutes, or (2) TDMAAs
The mixture was heated to about 515 ° C. in a mixed atmosphere of phosphorus and phosphorus. After that, at about 515 ° C., Be was doped with about 10 ¹⁸ / cm ^{3 of} I.
About 3000 Å of nGaAs was regrown. At that time, TEG (triethylgallium) was used as a Ga raw material, TMI (trimethylindium) was used as an In raw material, and pyrolyzed arsine and phosphine were used as As and P raw materials, respectively. The carrier concentration distribution in the depth direction is shown in FIG. TDM
When heated in the AAs atmosphere, the carrier concentration at the interface decreases by about one digit. On the other hand, when heated in a mixed atmosphere of TDMAAs and phosphorus, a substantially flat distribution is obtained. The morphology of the regrown thin film was visually a mirror surface, and no defect was observed with a Nomarski type differential interference microscope. Oxygen remaining at the interface of the two samples was examined by secondary ion mass spectrometry. TDMAA
When heated in an atmosphere, the oxygen concentration is approximately 10 ²⁰ / c
In contrast to m ³ , the oxygen concentration was 2 × 10 ¹⁸ / cm ³ when heated in a mixed atmosphere of TDMAAs and phosphorus. Also, the temperature and time during cleaning were examined. In the case of TDMAAs only, 515 ° C to 5
As the temperature increased to 25,535 ° C., the decrease in carrier concentration at the interface was slightly improved. That is,
In the case of 535 ° C., the decrease in carrier concentration at the interface was almost halved. At 515 ° C., no noticeable improvement was observed even if the cleaning time was extended to 15 minutes. On the other hand, in the case of a mixed atmosphere of TDMAAs and phosphorus, at 525 ° C., a flat distribution was obtained as in FIG. In the mixed atmosphere of TDMAAs and arsenic, the reduction action was not enhanced.

<Second Embodiment> An example in which the semiconductor thin film regrowth method of the present invention is applied to the formation of an electrode layer of a laser will be described. Using an MOCVD method, an n-type InP buffer layer (thickness 0.4 μm), InGaAsP (0.1 μm) having a wavelength of 1.3 μm composition, and InG are formed on an n-type InP substrate.
aAsP-MQW, InGaAs with wavelength 1.3 μm composition
P (0.1 μm), p-type InP (1.4 μm), p-type-wavelength 1.3 μm composition InGaAsP (0.2 μm), Zn
A 2000 Å doped InGaAs layer and finally an InP cap layer were grown. This is taken out into the air and InP
The cap layer was wet-etched. Then, it was left in the air for one week. After degreasing the sample, the sample was loaded into a CBE apparatus and heated at 525 ° C. for 5 minutes in a TDMAAs atmosphere or a mixed atmosphere of TDMAAs and phosphorus, and Zn-doped I
A 7 × 10 ¹⁹ / cm ³ concentration of carbon-doped InGaAs contact layer was regrown on the nGaAs layer. At that time, CBr ₄ was used as a carbon dope raw material. Further, this was processed into a mesa having a width of 1.5 μm, and a high resistance InP was grown on the side surface of the mesa by MOCVD to fill the mesa. TiPtAu was vapor-deposited on the contact layer to form a non-alloy electrode. The laser current-light output curve is shown in FIG. In the case of TDMAAs atmosphere cleaning, the light output saturates at about 17 mW, whereas in the mixed atmosphere of TDMAAs and phosphorus, the light output reaches about 30 mW. In this way, it was possible to realize a laser having a high optical output of 40% or more.

<Third Embodiment> Evaporation and removal of an oxide film by heating in a phosphorus (P molecule) atmosphere and growth of an InGaAsP thin film layer will be described. CBE was used for the thin film growth method. Ga
TEG (triethylgallium) was used as the raw material of, the TMI (trimethylindium) was used as the raw material of In, and thermally decomposed arsine and phosphine were used as the raw materials of As and P, respectively. Further, Be was used as the p-type dopant. First,
An InP buffer layer is grown on an n-type InP substrate, then InGaAs doped with Be 10 ¹⁸ / cm ³ as a p-type dopant is grown to 3000 Å, and finally In is grown.
The P cap layer was grown to 500 Å. This was taken out into the air, and the cap layer was wet-etched using a mixed solution of hydrochloric acid and phosphoric acid. This was inserted again into the CBE apparatus and heated in a phosphorus or arsenic atmosphere in order to clean the surface, and then, at 515 ° C., 3,000 liters of InGaAs doped with 10 ¹⁸ / cm ^{3 of} Be was regrown. FIG. 4 shows a carrier concentration distribution in the depth direction when heated in a phosphorus atmosphere. When the cleaning temperature (Tc) is 515 ° C., the carrier concentration at the interface decreases by about one digit. At the cleaning temperature of 575 ° C., the decrease in carrier concentration is almost eliminated. At a temperature in this range, the morphology of the regrown film was visually a mirror surface and even observed by a Nomarski differential interference microscope. Also, when heated in an arsenic atmosphere, a temperature tendency similar to that in FIG. 4 was shown, but to eliminate the decrease in carrier concentration at the interface, 585
C required. From these experiments, it was found that the surface oxide film of InGaAs was evaporated and removed at 570 ° C. or higher. However, heating to 600 ° C. or higher is not preferable because the element V is severely detached from the surface and the surface is roughened. InGaA doped with 10 ¹⁸ / cm ^{3 of} Be
Even when regrown to sP (wavelength 1.5 μm composition), a flat carrier distribution was obtained at a cleaning temperature of 570 ° C. or higher, as in FIG. FIG. 5 is an x-ray diffraction spectrum of the regrown InGaAs film when heated in a phosphorus atmosphere or an arsenic atmosphere. Regrown film thickness is 3000
Å and the cleaning temperature were both 575 ° C. The peak is clear when heated in a P atmosphere,
When heated in an As atmosphere, it is very broad and weak in strength. From the transmission electron microscope observation, it was found that many dislocations occurred in the latter. These results show that when heated in an arsenic atmosphere, the lattice constant of the surface layer deviates from InP, and thus regrown InG
While the crystallinity of the aAs film deteriorated, InGaAsP was formed on the surface when heated in a P atmosphere, and the lattice constant of InGaAsP was close to that of InP.
It can be interpreted that the As film has grown.

<Embodiment 4> The removal of an oxide film and the growth of a monoatomic layer or a multiatomic layer of InGaAsP by heating in a TDMAAs (trisdimethylaminoarsine) atmosphere will be described. CBE was used for the thin film growth method. TEG was used as a Ga raw material, TMI was used as an In raw material, and pyrolyzed arsine and phosphine were used as As and P raw materials, respectively. Further, Be was used as the p-type dopant. First, n
An InP buffer layer was grown on the type InP substrate, then InGaAs doped with Be as a p-type dopant of 10 ¹⁸ / cm ³ was grown 3000 Å, and finally an InP cap layer was grown 500 Å. This was taken out into the air, and the cap layer was wet-etched using a mixed solution of hydrochloric acid and phosphoric acid. This was placed again in the CBE apparatus and heated in a TDMAAs atmosphere to clean the surface, then
Being heated at 515 ° C. in a phosphorus atmosphere, the Be content is 10 ¹⁸ / cm 3.
^Three- doped InGaAs was regrown for 3000Å. FIG. 6 is a carrier concentration distribution in the depth direction when heated in a TDMAAs atmosphere. Cleaning temperature is 515
At temperatures above ℃, almost ideal carrier concentration distribution is obtained. In addition, from the measurement of AFM (atomic force microscope),
In when heated to 515 ° C. in TDMAAs atmosphere
It was found that the GaAs surface was flat at the atomic level. Therefore, when TDMAAs is used, the optimum cleaning temperature is 515 ° C. or higher. Also, this tendency is 54
It was also confirmed that it was possible to obtain up to 0 ° C. In this range, a sufficiently low interfacial oxygen concentration was obtained as compared with the method using a phosphorus atmosphere. InGaA doped with 10 ¹⁸ / cm ^{3 of} Be
Even when regrown to sP (wavelength 1.5 μm composition), an ideal carrier distribution was obtained in the cleaning temperature range of 515 to 540 ° C. as in FIG. 6. Regarding the regrown InGaAs film produced by the above method, the oxygen remaining at the interface was measured by SIMS (mass spectrometer). FIG. 7 is a summary of the results. When heated in a phosphorus atmosphere, residual oxygen exponentially decreased with increasing cleaning temperature. That is, the oxygen concentration at 515 ° C. is 5 × 10 ²⁰ / cm ³ , but at 575 ° C. it is 5 × 10 ²⁰ / cm ^3.
It was 10 ¹⁸ / cm ³ . On the other hand, the oxygen concentration when heated at 515 ° C. in the TDMAAs atmosphere is 5 × 10 ¹⁸ / c.
It was m ³ . These results mean that the hydrogen radicals generated from TDMAAs chemically react with the oxide film to effectively remove the oxide film.

<Embodiment 5> The semiconductor thin film regrowth method of the present invention is applied to an electrode layer of a laser. Using an MOCVD method, an n-type InP buffer layer (0.4 μm), 1.3Q (wavelength 1.3 μm InGaA) was formed on the n-type InP substrate.
sP, thickness 0.1 μm), InGaAsP-MQW, 1.
3Q (0.1 μm), p-type InP (1.4 μm), p-type 1.3Q (0.2 μm), Zn dove InGaAs layer 2
000Å, and finally the InP cap layer was grown. This was taken out in air and the InP cap layer was wet-etched. Then, it was loaded into a CBE apparatus and heated in a phosphorus or arsenic atmosphere at 575 ° C. for 5 minutes to obtain Zn-doped I
An InGaAs contact layer doped with carbon at a concentration of 10 ²⁰ / cm ³ was regrown on the nGaAs layer. At that time, CBr ₄ was used as a carbon dope raw material. Further, this was processed into a mesa having a width of 1.5 μm, and a high resistance InP was grown on the side surface of the mesa by MOCVD to fill the mesa. TiPtAu was vapor-deposited on the conduct layer to form a non-alloy electrode. The current / light output curve of the laser when heated in a phosphorus atmosphere is shown in FIG. Cleaning temperature is 5
15 ° C. and 575 ° C. The threshold currents of the two are almost the same, but the laser whose cleaning temperature is 575 ° C
The light output was 30% or more higher than that at 515 ° C. Further, the cleaning temperature was fixed at 575 ° C., and the influence of phosphorus or arsenic atmosphere was also examined. Both current and light output curves were almost the same. However, the result of the aging test at 50 ° C shows that the laser produced by cleaning in the phosphorus atmosphere showed almost no change in the current / light output curve with respect to time. Some elements were observed to deteriorate. This is considered to be the influence of the distortion described in the first embodiment. Although the case of forming the non-alloy contact layer has been described in the present embodiment, it has been confirmed that the same effect as described above can be obtained even when applied to other portions of the semiconductor element.
Although it has been described in the present embodiment that the present invention is effective for improving the laser, it goes without saying that the present invention can also be applied to improving the characteristics of an optical device that requires thin film regrowth, for example, a photodetector. Yes. In the above embodiment, I
The removal of the oxide film on the semiconductor layer made of nGaAs or InGaAsP and the formation of the semiconductor layer for relaxing the lattice strain have been described, but in the removal of the oxide film on the semiconductor layer made of InP and the formation of the semiconductor layer for relaxing the lattice strain. It has been confirmed that the semiconductor thin film regrowth method of the present invention can be applied and the effects of the present invention can be obtained.

[0012]

According to the method of regrowth of a semiconductor thin film of the present invention, an oxide film on a semiconductor layer made of InGaAs or InGaAsP is treated with trisdimethylaminoarsine (T).
After DMAAs) and heated in a mixed atmosphere containing phosphorus (P molecule), it can be properly heated in an atmosphere containing TDMAAs, by heating in an atmosphere containing phosphorus (P molecules), effectively a surface oxide film In addition, the thin film layer made of InGaAsP or the like, which relaxes the lattice strain, can be formed on the outermost surface of the semiconductor layer by heating in an atmosphere containing phosphorus.
The -V compound semiconductor layer can be effectively regrown, and a semiconductor film having good crystallinity with no strain accumulation at the growth interface and no defects can be obtained with high yield. For example, the optical output of the semiconductor laser can be increased by 40% or more, and there is an effect that it can contribute to the characteristic improvement of optical devices such as an optical modulator and a photodetector.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a cross-sectional structure of a photodetector to which a semiconductor thin film regrowth method of the present invention can be applied.

FIG. 2 is a graph showing a carrier concentration distribution in the depth direction illustrated in the first embodiment of the present invention.

FIG. 3 is a graph showing a current-light output curve of the laser exemplified in the second embodiment of the present invention.

FIG. 4 is a graph showing a carrier concentration distribution in the depth direction when heated in a P atmosphere exemplified in the third embodiment of the present invention.

FIG. 5 shows P or As exemplified in the third embodiment of the present invention.
6 is a graph showing an x-ray diffraction spectrum of the regrown InGaAs film when heated in an atmosphere.

FIG. 6 is a schematic diagram of TDMAAs illustrated in a fourth embodiment of the present invention.
The graph which shows the carrier concentration distribution of the depth direction at the time of heating in an atmosphere.

FIG. 7 is a graph showing the effects of the cleaning temperature and the heating atmosphere on the oxygen concentration remaining at the interface exemplified in the fourth embodiment of the present invention.

FIG. 8 is a curve showing the relationship between the laser current and the optical output at each cleaning temperature illustrated in the fifth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... n-type InP substrate 2 ... n-type InP buffer layer 3 ... active layer 4 ... p-type InP layer 5 ... electrode contact layer 6 highly doped with p-type dopant ... InP cap layer 7 ... metal electrode 8 ... carbon Highly doped regrown electrode contact layer

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-116236 (JP, A) JP-A-8-88185 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/205 H01L 21/203 H01L 21/28 301

Claims (6)

(57) [Claims] 1. A thin film growth method for growing a III-V group compound semiconductor in a vacuum chamber, comprising: InGaAs or I
A method of re-growing a second semiconductor layer made of a III-V group compound semiconductor lattice-matched with the first semiconductor layer on the first semiconductor layer made of nGaAsP, comprising: Prior to regrowth, the first semiconductor layer is heated in a mixed atmosphere containing trisdimethylaminoarsine and phosphorus to remove and clean the surface oxide film, and at the A method of regrowing a semiconductor thin film, comprising a step of forming a semiconductor layer having a composition for relaxing lattice strain on a surface thereof. 2. The heating temperature in a mixed atmosphere containing trisdimethylaminoarsine and phosphorus according to claim 1,
A method of regrowing a semiconductor thin film, which is in the range of 15 to 540 ° C. 3. The method for regrowth of a semiconductor thin film according to claim 1, wherein the surface oxide film of the first semiconductor layer is removed by heating in a mixed atmosphere containing trisdimethylaminoarsine and phosphorus. At the same time, after the step of forming a semiconductor layer having a composition that relaxes the lattice strain, a step of re-growing p-type InGaAs heavily doped with carbon is subsequently included. 4. A second semiconductor layer made of a III-V group compound semiconductor lattice-matched with the first semiconductor layer is regrown on the first semiconductor layer made of InGaAs or InGaAsP formed on a substrate. A method of removing the surface oxide film by heating the first semiconductor layer in an atmosphere containing trisdimethylaminoarsine before regrowth of the second semiconductor layer; Which is heated to a high temperature in an atmosphere containing Al and relaxes the lattice strain on the outermost surface of the first semiconductor layer.
And a step of regrowth of a second semiconductor layer made of a III-V group compound semiconductor on the thin film layer made of InGaAsP. 5. The method for regrowing a semiconductor thin film according to claim 4, wherein the heating temperature in the atmosphere of trisdimethylaminoarsine is in the range of 515 to 540 ° C. 6. The method of regrowing a semiconductor thin film according to claim 4 or 5 , wherein InGaAs is used for relaxing lattice distortion.
The second semiconductor layer made of a III-V group compound semiconductor that regenerates on the thin film layer made of P is a non-alloy semiconductor electrode layer made of p-type InGaAs doped with carbon at a high concentration. Thin film regrowth method.