JP2010225981A - Optical semiconductor device, integrated element and method of manufacturing optical semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce diffusion of Ge and to obtain excellent device characteristics in an optical semiconductor element comprising an active layer containing GaAs. <P>SOLUTION: An optical semiconductor device includes: a Ge layer 2; a first GaAs layer 3 which is formed on the Ge layer 2 and in which an As site of GaAs is partially substituted with Ga; and an active layer 4, containing GaAs, formed above the first GaAs layer 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical semiconductor element, an integrated element, and a method for manufacturing an optical semiconductor element.

As an application of Si photonics, an optical semiconductor element having a highly efficient GaAs-based active layer on a Si substrate is required.
For example, since Si and GaAs have a large lattice mismatch, a graded composition Si _1-x Ge _x (0 ≦ x ≦ 1) layer is grown on the Si substrate to reduce the lattice mismatch with GaAs, thereby increasing the GaAs type. There is a technique for forming an active layer.

  In this technology, migration enhanced epitaxy (MEE) that alternately supplies Ga and As using a molecular beam epitaxy (MBE) apparatus at a growth temperature of 250 ° C. under an extremely low temperature condition. A GaAs initial layer having a thickness of 10 atomic layers is formed on the Ge layer by the unique raw material supply method. Then, GaAs is grown on the GaAs initial layer at a general growth temperature of 580 ° C. to form a GaAs-based active layer.

H. Tanoto et al., “Structural and optical properties of stacked self-assembled InAs / InGaAs quantum dots on graded Si1-xGex / Si substrate”, APPLIED PHYSICS LETTERS 92, 213115 (2008)

By the way, in the vapor phase growth method such as the ultra high vacuum chemical vapor deposition (UHV-CVD) method or the metal organic vapor phase epitaxy (MOVPE) method, the As raw material is used. A compound such as arsine (AsH ₃ ) is used.
For this reason, when forming a GaAs layer on a Ge layer, it is necessary to raise the growth temperature to about 500 ° C. so that the raw material is decomposed. In this case, Ge diffuses into GaAs, and the impurity concentration of the GaAs layer becomes high, which may affect device characteristics.

  Therefore, in an optical semiconductor element having an active layer containing GaAs, it is desired to obtain good device characteristics with less Ge diffusion.

For this reason, this optical semiconductor device includes a Ge layer, a first GaAs layer formed on the Ge layer, a part of the As site of GaAs being replaced with Ga, and GaAs formed above the first GaAs layer. It is a requirement to provide an active layer containing.
The integrated element includes an optical semiconductor element and a functional element. The optical semiconductor element and the functional element are integrated on the same substrate. The optical semiconductor element is formed on a Ge layer and a Ge layer. It is a requirement to include a first GaAs layer in which a part of the As site is replaced with Ga, and an active layer containing GaAs formed above the first GaAs layer.

  In this method of manufacturing an optical semiconductor device, a first GaAs layer is formed on a Ge layer by vapor phase growth with an effective V / III ratio obtained by multiplying a supply V / III ratio by decomposition efficiency to 1 or more and 2 or less. It is necessary to form a GaAs-based active layer above the first GaAs layer.

  Therefore, according to the manufacturing method of the present optical semiconductor element, integrated element, and optical semiconductor element, there is an advantage that good device characteristics can be obtained with less Ge diffusion.

It is typical sectional drawing which shows the structure of the optical semiconductor element concerning 1st Embodiment. It is a SIMS profile which shows Ge concentration distribution in GaAs in sample (a), (b). It is a figure which shows PL spectrum of the sample (b) which shows the light emission which the antisite atom involved. It is a figure which shows the atomic arrangement | positioning of GaAs with which the part of As site with which the optical semiconductor element concerning 1st Embodiment is substituted by Ga is provided. (A) shows the relationship of growth temperature, decomposition efficiency, supply V / III ratio with an effective V / III ratio of 1 and supply V / III ratio with an effective V / III ratio of 2 with respect to AsH ₃ . (B) shows the growth temperature, decomposition efficiency, supply V / III ratio with an effective V / III ratio of 1 and supply V with an effective V / III ratio of 2 with respect to TBAs. It is a figure which shows the relationship of / III ratio. It is a SIMS profile which shows Ge concentration distribution in GaAs in sample (a)-(c). It is a typical sectional view showing the composition of the optical semiconductor device (ridge type quantum dot laser) concerning a 2nd embodiment. It is a typical sectional view showing the composition of the optical semiconductor device (surface emitting quantum well laser) concerning a 3rd embodiment.

Hereinafter, a method for manufacturing an optical semiconductor element, an integrated element, and an optical semiconductor element according to the present embodiment will be described with reference to the drawings.
[First Embodiment]
The optical semiconductor device and the manufacturing method thereof according to the first embodiment will be described with reference to FIGS.

  In the optical semiconductor device (light emitting device; optical device) according to the present embodiment, for example, as shown in FIG. 1, a Ge layer 2 and a part of an As site of GaAs are substituted with Ga on a Si substrate 1. A first GaAs layer 3 and a GaAs-based active layer (active layer containing GaAs; III-V compound semiconductor active layer; light emitting layer) 4 are provided. That is, in this optical semiconductor element, the Si buffer layer and the Ge layer 2 (not shown) are formed on the Si substrate 1. Further, a first GaAs layer 3 in which a part of the As site of GaAs is substituted with Ga is formed on the Ge layer 2. A GaAs-based active layer 4 is formed above the first GaAs layer 3.

Here, the GaAs-based active layer 4 is a GaAs-based light emitting layer formed of a combination of materials that can be grown so as to lattice match with GaAs without causing defects such as dislocations on the GaAs. Note that a light emitting element including the GaAs light emitting layer 4 is also referred to as a GaAs light emitting element.
For example, combinations of quantum wells (or quantum wires, quantum dots) / barrier layers constituting the GaAs-based active layer 4 include InAs / GaAs, InGaAs / GaAs, InAs / AlGaAs, InGaAs / AlGaAs, InGaAsSb / AlGaAs, InGaAsN / Examples include AlGaAs and InGaAsP / AlGaAs.

  In the present embodiment, a GaAs / InGaAs / GaAs quantum well layer is formed as the GaAs-based active layer 4. For this reason, the present optical semiconductor device includes an Si buffer layer (not shown), a Ge layer 2, a first GaAs layer 3 in which a part of the As site of GaAs is replaced with Ga, and a GaAs layer (barrier layer) on the Si substrate 1. 5, an InGaAs layer (well layer) 6 and a GaAs layer (barrier layer) 7 are sequentially stacked.

Although the Si substrate 1 is used here, any substrate may be used as long as it is a substrate (a substrate containing Si) made of a Si-based material (that is, Si or a group IV semiconductor mixed crystal containing Si). In this specification, the term Si substrate includes a substrate containing Si. Further, instead of the Si buffer layer and Ge layer 2 (not shown), a gradient composition Si _1-x Ge _x (0 ≦ x ≦ 1) layer may be formed. The Si substrate on which the gradient composition Si _1-x Ge _x (0 ≦ x ≦ 1) layer is formed is also referred to as a Si substrate having a relaxed Ge layer. In this case, the Ge layer constituting the uppermost surface of the gradient composition Si _1-x Ge _x (0 ≦ x ≦ 1) layer corresponds to the Ge layer 2 described above.

By the way, in this optical semiconductor device, as described above, the first GaAs in which a part of the As site of GaAs is substituted with Ga on the Ge layer 2, that is, between the Ge layer 2 and the GaAs-based active layer 4. Layer 3 is formed.
For this reason, the diffusion of Ge into GaAs constituting the GaAs-based active layer 4 can be reduced. As a result, an optical semiconductor element including the GaAs-based active layer 4 having a small amount of Ge impurities mixed by diffusion and having good light emission characteristics on the Ge layer 2 can be realized.

In particular, when a compound such as arsine (AsH ₃ ) is used as the As raw material in a vapor phase growth method such as UHV-CVD method or MOVPE method, the growth temperature needs to be raised to, for example, about 500 ° C. so that the raw material is decomposed. There is. Even in such a case, the diffusion of Ge into GaAs constituting the GaAs-based active layer 4 can be reduced, and good light emission characteristics can be obtained. That is, even when an optical semiconductor device having a GaAs-based active layer on a Ge layer formed on a Si substrate by the general growth method as described above, Ge diffusion is small and good. An optical semiconductor device including the GaAs-based active layer 4 having light emission characteristics can be realized.

Here, the experimental results obtained by the growth by the UHV-CVD method for the diffusion of Ge into GaAs will be described.
FIG. 2 shows the Ge concentration in the GaAs layer as a secondary ion mass in samples (a) and (b) in which a GaAs layer having a thickness of about 0.23 μm is grown after the Ge layer is grown on the Si substrate. It is the result measured by analysis (SIMS; Secondary Ion Mass Spectrometry) method.

Here, in both the samples (a) and (b), the growth temperature of the GaAs layer was 490 ° C. for the first about 0.115 μm, and 600 ° C. for the subsequent about 0.115 μm. In this case, a GaAs layer having a thickness of about 0.115 μm and a GaAs layer having a thickness of about 0.115 μm are formed.
In the sample (a), a GaAs layer was grown with the supply ratio (supply V / III ratio) of AsH ₃ and triethylgallium (TEGa) set to 50. In this case, as shown in FIG. 2, the diffusion of Ge into the GaAs layer was remarkable, and the shift of the Ge layer interface to the GaAs layer side and the Ge impurity diffusion of about 10 ¹⁹ cm ⁻³ were confirmed.

On the other hand, Sample (b) was grown with a GaAs layer with a supply V / III ratio of 20. In this case, as shown in FIG. 2, it has been found that the diffusion of Ge into the GaAs layer is dramatically suppressed. In particular, it has been found that the diffusion of Ge is suppressed by the first GaAs layer.
Note that the Ge concentration value fluctuates around 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁸ cm ⁻³ in the GaAs region of the sample (b) because the detection limit concentration of Ge by the SIMS method is 5 ×. Since it is based on 10 ¹⁷ cm ⁻³ , the actual Ge concentration of the sample (b) is estimated to be 10 ¹⁷ cm ⁻³ or less.

By the way, it has been found that the effect obtained by the difference in the growth conditions is that the GaAs crystal has a characteristic structure due to the difference in the growth conditions.
Here, FIG. 3 shows a spectrum when the sample (b) in which the diffusion of Ge is suppressed is measured by photoluminescence (PL) at a temperature of 5K.
As shown in FIG. 3, light emission was observed at a wavelength of 862 nm longer than the emission wavelength of 820 nm at the band edge of GaAs.

  This is shown, for example, in M. Bugajski et al., “Native acceptor levels in Ga-rich GaAs”, J. Appl. Phys. Vol. 65, No. 2, pp. 596-599, 15 January 1989). In addition, light emission is caused by an antisite atom in which a part of the As site of the GaAs layer is replaced with Ga. That is, when there is an antisite atom in which a part of the As site of the GaAs layer is replaced with Ga, that is, when the GaAs layer has a characteristic crystal as shown in FIG. Was found to be suppressed.

As a result of the examination, it was found that such a Ge diffusion suppression effect is caused by the following mechanism.
Ge is likely to enter a Ga site as an n-type impurity in GaAs.
However, when GaAs is grown under As-rich growth conditions [sample (a)], vacancies are easily formed at the Ga site, and Ge atoms entering the Ga site easily diffuse while replacing the vacancies. Can do.

On the other hand, when GaAs is grown under the Ga-rich growth condition [sample (b)], Ga is present up to a part of the As site, and since there is no Ga site vacancy, the diffusion of Ge is suppressed. The
In the above experiment, GaAs in which a part of the As site is substituted with Ga is obtained because the effective V / III ratio obtained by multiplying the supply V / III ratio by the decomposition efficiency (raw material decomposition efficiency). It was found that this was a case where characteristic growth conditions (Ga rich) of 2 or less were used.

In the sample (b) in which the diffusion of Ge is suppressed, the supply V / III ratio is set to 20 as described above. In other words, the supply amount of the raw material is 20 times that of AsH ₃ with respect to TEGa.
However, the raw material decomposition efficiency of AsH _{3 at} a temperature of 490 ° C. is about 10%.
The ratio of the As raw material to the Ga raw material effective for growth, that is, the effective V / III ratio, can be derived from the supplied V / III ratio × the decomposition efficiency. In the case of the above experiment, the effective V / III ratio is 20 × 0.1 = 2. That is, the As raw material effective for growth is doubled with respect to the Ga raw material effective for growth.

  Considering the details of crystal growth, the As element that can actually exist on the substrate surface is multiplied by the above effective V / III ratio and the efficiency of heat conduction to the raw material on the substrate surface. Therefore, it is considered that it was less than 1, which is half the effective V / III ratio. It can be considered that this was an environment in which GaAs in which part of the As site was replaced with Ga grew.

  On the other hand, if the amount of As raw material that contributes to growth is too small relative to Ga, crystal growth of GaAs becomes impossible, but the growth temperature is the same as that of sample (b), and the V / III ratio as a supply ratio is set to 10. It was found that GaAs grows even under growth conditions. From this, it was found that when at least the effective V / III ratio is 1 or more, a GaAs layer in which part of the As site is substituted with Ga can be obtained.

By the way, since the effective V / III ratio is related to the decomposition efficiency of the V group raw material, the supply V / III is set to an effective V / III ratio of 1 or more and 2 or less depending on the kind of the V group raw material and the growth temperature. The ratio value (that is, the value of the supplied V / III ratio from which a GaAs layer in which a part of the As site is substituted with Ga) is different.
For example, in the vapor phase growth method such as the UHV-CVD method and the MOVPE method, AsH ₃ and tertiary butylarsine (TBAs) are generally used as the As raw material.

Here, FIGS. 5A and 5B show the growth temperature, decomposition efficiency, supply V / III ratio at which the effective V / III ratio is 1, and effective V / III ratio for each raw material. The relationship of the supply V / III ratio which becomes 2 is shown.
For example, when AsH ₃ is used as the As raw material, as shown in FIG. 5A, when the growth temperature is set to 550 ° C., the decomposition efficiency is 30%, so the effective V / III ratio is 1 In order to make it 2 or less, the supply V / III ratio should be 3.4 or more and 6.6 or less.

When the growth temperature is set to 530 ° C., the decomposition efficiency is 20%. Therefore, in order to make the effective V / III ratio 1 or more and 2 or less, the supply V / III ratio is 5 or more and 10 or less. I will do it.
When the growth temperature is set to 510 ° C., the decomposition efficiency is 15%. Therefore, in order to make the effective V / III ratio 1 or more and 2 or less, the supply V / III ratio is 6.7 or more and 13 The following should be done.

When the growth temperature is set to 490 ° C., the decomposition efficiency is 10%. Therefore, in order to make the effective V / III ratio 1 or more and 2 or less, the supply V / III ratio is made 10 or more and 20 or less. I will do it.
When the growth temperature is set to 470 ° C., the decomposition efficiency is 5%. Therefore, in order to make the effective V / III ratio 1 or more and 2 or less, the supply V / III ratio is 20 or more and 40 or less. I will do it.

When the growth temperature is set to 450 ° C., the decomposition efficiency is 2%. Therefore, in order to set the effective V / III ratio to 1 or more and 2 or less, the supply V / III ratio is set to 50 or more and 100 or less. I will do it.
Thus, when AsH ₃ is used as the As raw material, the growth temperature is set in the range of 350 ° C. to 550 ° C., for example, and the decomposition efficiency that changes in the range of 2% to 30% according to the growth temperature If the value of the supply V / III ratio is set so that the effective V / III ratio is 1 or more and 2 or less, a GaAs layer in which part of the As site is replaced with Ga is obtained. It will be.

Also, for example, when TBAs is used as the As raw material, as shown in FIG. 5B, when the growth temperature is set to 450 ° C., the decomposition efficiency is 100%, so the effective V / III ratio is In order to make it 1 or more and 2 or less, the supply V / III ratio should be 1 or more and 2 or less.
When the growth temperature is set to 430 ° C., the decomposition efficiency is 90%. Therefore, in order to make the effective V / III ratio 1 or more and 2 or less, the supply V / III ratio is 1.2 or more and 2 .2 or less.

Further, when the growth temperature is set to 410 ° C., the decomposition efficiency is 80%. Therefore, in order to make the effective V / III ratio 1 or more and 2 or less, the supply V / III ratio is 1.3 or more and 2 .5 or less is sufficient.
When the growth temperature is set to 390 ° C., the decomposition efficiency is 60%. Therefore, in order to make the effective V / III ratio 1 or more and 2 or less, the supply V / III ratio is 1.7 or more and 3 or less. .3 or less.

When the growth temperature is set to 370 ° C., the decomposition efficiency is 30%. Therefore, in order to make the effective V / III ratio 1 or more and 2 or less, the supply V / III ratio is 3.4 or more and 6 or less. .6 or less is sufficient.
Further, when the growth temperature is set to 350 ° C., the decomposition efficiency is 10%. Therefore, in order to make the effective V / III ratio 1 or more and 2 or less, the supply V / III ratio is made 10 or more and 20 or less. I will do it.

  Thus, when TBAs is used as the As raw material, the growth temperature is set in the range of 350 ° C. to 450 ° C., and based on the growth temperature and the decomposition efficiency that changes in the range of 10% to 100% depending on the growth temperature. If the value of the supply V / III ratio is set so that the effective V / III ratio is 1 or more and 2 or less, a GaAs layer in which part of the As site is replaced with Ga can be obtained. Become.

  By the way, in the sample (a) described above, the first GaAs layer is formed at a supply V / III ratio of 50 and the growth temperature is 490 ° C., and the second GaAs layer is formed at a supply V / III ratio. 50 and a growth temperature of 600 ° C., each GaAs layer is not a GaAs layer in which part of the As site is replaced with Ga, but a GaAs layer having a normal crystal structure. ing.

  On the other hand, in the above-described sample (b), the first GaAs layer is formed at a supply V / III ratio of 20 and a growth temperature of 490 ° C., so that the effective V / III ratio is 1 or more. 2 or less. For this reason, the first GaAs layer is a GaAs layer in which part of the As site is replaced with Ga. On the other hand, the second GaAs layer is formed with a supply V / III ratio of 20 and a growth temperature of 600 ° C., so it is not a GaAs layer in which part of the As site is replaced with Ga. The GaAs layer has a normal crystal structure.

In these samples (a) and (b), the supply V / III ratio was constant in both layers, but even if the supply V / III ratio was changed between the first layer and the second layer, part of the As site It was further confirmed that if a GaAs layer substituted with Ga is present at the interface with Ge, the effect of suppressing the diffusion of Ge can be obtained without depending on the GaAs layer grown thereon.
Here, FIG. 6 shows that after the first GaAs layer is grown at a thickness of 0.1 μm, the supply V / III ratio is 20, and the growth temperature is 490 ° C., the second GaAs layer has a thickness of 0. The result of measuring the Ge concentration in the GaAs layer by the SIMS method in the sample (c) grown at 1 μm, supply V / III ratio 50, and growth temperature 600 ° C. is shown together with the measurement results of the samples (a) and (b). Show.

  In the sample (c), since the first GaAs layer is formed with a supply V / III ratio of 20 and a growth temperature of 490 ° C., the effective V / III ratio is 1 or more and 2 or less. It has become. For this reason, the first GaAs layer is a GaAs layer in which part of the As site is replaced with Ga. On the other hand, the second GaAs layer is formed at a supply V / III ratio of 50 and a growth temperature of 600 ° C., so it is not a GaAs layer in which part of the As site is replaced with Ga. The GaAs layer has a normal crystal structure.

  As shown in FIG. 6, since the first GaAs layer suppresses the diffusion of Ge, the Ge impurity concentration of the entire GaAs layer is suppressed low without depending on the second GaAs layer. I understand. That is, it can be seen that the GaAs layer in contact with the Ge layer is important for suppressing the diffusion of Ge. This is because if a GaAs layer in which part of the As site is replaced with Ga is formed as a GaAs layer in contact with the Ge layer, the GaAs layer formed thereon can be grown under any growth conditions. Means you can.

Next, a method for manufacturing the optical semiconductor element according to the present embodiment will be described.
In the manufacturing method of the optical semiconductor element, first, the Ge layer 2 is formed on the Si substrate 1 (see FIG. 1).
Next, the effective V / III ratio obtained by multiplying the supply V / III ratio by the decomposition efficiency is set to 1 to 2 on the Ge layer 2 by, for example, a vapor phase growth method such as UHV-CVD method or MOVPE method. A 1GaAs layer 3 is formed (see FIG. 1).

Next, a GaAs / InGaAs / GaAs quantum well layer as a GaAs-based active layer 4 is formed above the first GaAs layer 3 (see FIG. 1).
In the present embodiment, the effective V / III ratio obtained by multiplying the supply V / III ratio by the decomposition efficiency is made larger than 2 on the first GaAs layer 3 by vapor phase epitaxy, and the GaAs / InGaAs / GaAs quantum is obtained. A GaAs layer 5 (second GaAs layer) constituting the lowermost layer of the well layer 4 is formed (see FIG. 1).

Specifically, it can be produced as follows by, for example, UHV-CVD.
First, the Si substrate 1 is heated to 650 to 750 ° C., for example. After the temperature is stabilized, by supplying disilane (Si ₂ H ₆ ), an Si buffer layer (not shown) is grown to a thickness of 100 nm (epitaxial growth), for example.

Next, the substrate temperature is lowered to 350 to 550 ° C., for example, and germane (GeH ₄ ) is supplied to grow a Ge layer 2 on the Si buffer layer (not shown), for example, to a thickness of 50 to 200 nm (see FIG. 1). ).
Next, on the Ge layer 2, the growth temperature (substrate temperature) is 490 ° C., the supply of AsH ₃ as the As raw material and TEGa as the Ga raw material is V / III ratio 20 (effective V / III ratio 2), and GaAs The layer 3 is grown to a thickness of 50 to 500 nm, for example. As a result, the first GaAs layer 3 in which part of the As site is replaced with Ga is formed on the Ge layer 2 (see FIG. 1).

Thereafter, the growth temperature is raised to 600 ° C., and a GaAs layer 5 (second GaAs layer) is formed on the first GaAs layer 3 with a thickness of 50, for example, with a supply V / III ratio of AsH ₃ as As material and TEGa as Ga material. Grow 50 to 500 nm (see FIG. 1).
Next, an InGaAs layer 6 is grown on the GaAs layer 5 to a thickness of 1 to 10 nm, for example, and a GaAs cap layer 7 is grown to a thickness of 50 to 500 nm, for example. Thereby, a GaAs / InGaAs / GaAs quantum well layer (active layer) 4 is formed on the first GaAs layer 3 (see FIG. 1).

In this way, the present optical semiconductor element is manufactured.
Therefore, according to the optical semiconductor device and the method for manufacturing the same according to the present embodiment, in the optical semiconductor device including the GaAs-based active layer 4 on the Si substrate 1 with the Ge layer 2 interposed therebetween, Ge diffusion is small and a good device is obtained. There is an advantage that characteristics (light emission characteristics) can be obtained.
[Second Embodiment]
The optical semiconductor device and the manufacturing method thereof according to the second embodiment will be described with reference to FIG.

The optical semiconductor device according to this embodiment is a ridge type semiconductor quantum dot laser to which the present invention is applied.
As shown in FIG. 7, the ridge-type quantum dot laser includes a GaAs quantum dot active layer (active layer containing GaAs) 4A instead of the GaAs quantum well active layer 4 of the first embodiment. Type quantum dot laser. That is, this ridge type quantum dot laser is a Si type ridge type quantum dot laser (Si type light emitting device) including a GaAs type quantum dot active layer 4A above a Ge layer 2A formed on a Si substrate 1A. In FIG. 7, the same components as those in the first embodiment described above (see FIG. 1) are denoted by the same reference numerals.

  That is, as shown in FIG. 7, the ridge-type quantum dot laser has a p-type Si buffer layer (p-type Si layer; not shown) on the p-type Si substrate 1A in order from the substrate side. p-type Ge layer 2A, GaAs layer 3 (first GaAs layer) in which part of the As site is replaced with Ga, n-type GaAs layer 10 (contact layer; second GaAs layer), n-type AlGaAs layer 11 (cladding layer) A multilayer GaAs / InAs quantum dot active layer 4A (GaAs-based active layer; III-V compound semiconductor active layer; light-emitting layer), p-type AlGaAs layer 12 (cladding layer), and p-type GaAs layer 13 (contact layer) are stacked. A stacked semiconductor structure. FIG. 7 illustrates an active layer 4A including two quantum dot layers.

The ridge-type quantum dot laser has a ridge structure including an n-type AlGaAs layer 11, a multilayer GaAs / InAs quantum dot active layer 4A, a p-type AlGaAs layer 12, and a p-type GaAs layer 13.
A p-side electrode 14 is formed of metal on the surface of the p-type GaAs layer 13, and an n-side electrode 15 is formed of metal on the surface of the n-type GaAs layer 10.

Next, a method for manufacturing the optical semiconductor element (ridge type quantum dot laser) according to the present embodiment will be described.
In the present embodiment, crystal growth is performed by, for example, UHV-CVD.
First, the p-type Si (100) substrate 1A is heated to 650 to 750 ° C., for example. After the temperature is stabilized, for example, by supplying disilane (Si ₂ H ₆ ) or diborane (B ₂ H ₆ ), a p-type Si buffer layer (not shown) is grown to a thickness of 100 nm, for example.

Next, the substrate temperature is lowered to, for example, 350 to 550 ° C., and germanium (GeH ₄ ) and B ₂ H ₆ are supplied, for example, to epitaxially grow the p-type Ge layer 2A, for example, 50 to 200 nm (see FIG. 7). The p-type impurity concentration is, for example, 1 × 10 ¹⁷ cm ⁻³ .
Next, on the p-type Ge layer 2A, the growth temperature (substrate temperature) is 490 ° C., the supply of AsH ₃ as the As raw material and TEGa as the Ga raw material is 20 (effective V / III ratio 2). The GaAs layer 3 is grown to a thickness of 50 to 500 nm, for example. As a result, the first GaAs layer 3 in which part of the As site is replaced with Ga is formed on the p-type Ge layer 2A (see FIG. 7).

Next, the growth temperature is raised to, for example, 550 to 650 ° C., and an n-type GaAs layer 10 (second GaAs layer) is formed on the first GaAs layer 3 with a supply V / III ratio of AsH ₃ as the As material and TEGa as the Ga material. ) Is grown to a thickness of 50 to 500 nm, for example (see FIG. 7).
Next, an n-type AlGaAs layer 11 is grown on the n-type GaAs layer 10 by, for example, 100 to 1000 nm (see FIG. 7).

Next, the growth temperature is lowered to, for example, 450 to 500 ° C., and the GaAs layer 4a (barrier layer) is grown on the n-type AlGaAs layer 11 by, for example, 30 to 40 nm (see FIG. 7).
Next, the InAs quantum dots 4b are grown, for example, with a supply amount of 2 to 4 ML and a V / III ratio of 5 to 20 (see FIG. 7).
Such a process is repeated to form a multilayer GaAs / InAs quantum dot active layer 4A having a plurality of quantum dot layers including the GaAs layer 4a and the InAs quantum dots 4b. As a result, a multilayer GaAs / InAs quantum dot active layer 4A as a GaAs-based active layer is formed on the n-type AlGaAs layer 11 (see FIG. 7). The quantum dot active layer 4A is preferably a multilayer because the gain is increased, but may be a single layer.

Thereafter, the growth temperature is raised to, for example, 550 to 650 ° C., and the p-type AlGaAs layer 12 is grown to, for example, 100 to 1000 nm on the multilayer GaAs / InAs quantum dot active layer 4A (see FIG. 7). For example, C may be used as the p-type impurity, and the impurity concentration is, for example, 1 × 10 ¹⁸ cm ⁻³ .
Next, the p-type GaAs layer 13 is grown on the p-type AlGaAs layer 12 by, for example, 100 to 300 nm (see FIG. 7). The impurity concentration is, for example, 1 × 10 ¹⁹ cm ⁻³ .

After forming the semiconductor multilayer structure in this way, a ridge structure including the n-type AlGaAs layer 11, the multilayer GaAs / InAs quantum dot active layer 4A, the p-type AlGaAs layer 12, and the p-type GaAs layer 13 is formed by lithography and etching, for example. Form (see FIG. 7).
Thereafter, the p-side electrode 14 is formed on the surface of the p-type GaAs layer 13, and the n-side electrode 15 is formed on the surface of the n-type GaAs layer 10. Then, an end face in the axial direction from which light is emitted is formed by cleavage, and a cavity (resonator structure) is formed. In this way, a ridge type quantum dot laser is manufactured.

Since other details are the same as those of the first embodiment described above, the description thereof is omitted here.
Therefore, according to the optical semiconductor device and the manufacturing method thereof according to the present embodiment, as in the case of the first embodiment described above, the optical semiconductor including the GaAs-based active layer 4A on the Si substrate 1A via the Ge layer 2A. In the element, there is an advantage that Ge can be diffused and good device characteristics can be obtained.

  In the present embodiment, the description has been given by taking as an example a light emitting layer having a quantum dot structure, but the present invention is not limited to this. For example, as in the first embodiment described above, a light emitting layer having a GaAs / InGaAs / GaAs quantum well structure (or multiple quantum well structure) may be provided, or a light emitting layer having another structure may be provided. You may comprise as a thing.

In this embodiment, the ridge type quantum dot semiconductor laser is described as an example, but the present invention is not limited to this. In the present invention, for example, a buried quantum dot semiconductor laser or a quantum dot semiconductor laser having a diffraction grating [DFB (Distributed Feed-Back) laser or DBR (Distributed) is used as long as it has a GaAs-based active layer above a Ge layer. BraggReflector) etc. can be widely applied.
[Third Embodiment]
An optical semiconductor device and a manufacturing method thereof according to the third embodiment will be described with reference to FIG.

The optical semiconductor device according to the present embodiment is a surface emitting laser (VCSEL; vertical cavity surface emitting laser) to which the present invention is applied.
As shown in FIG. 8, the surface emitting laser is a surface emitting laser (surface emitting quantum well laser) having a GaAs multiple quantum well active layer in which a plurality of GaAs quantum well layers according to the first embodiment are stacked. is there. That is, this surface-emitting laser is a Si-based surface-emitting laser (Si-based vertical cavity light-emitting element) including a GaAs-based active layer (active layer containing GaAs) 4B above a Ge layer 2B formed on a Si substrate 1B. ). In FIG. 8, the same components as those in the first embodiment described above (see FIG. 1) are denoted by the same reference numerals.

In other words, as shown in FIG. 8, this surface emitting laser has a p-type Ge layer 2B and a GaAs layer in which part of an As site is replaced with Ga on the p-type Si substrate 1B in order from the substrate side (first layer). 1 GaAs layer) 3, lower n-type GaAs / AlGaAs multilayer DBR mirror 20, GaAs / InGaAs / GaAs multiple quantum well active layer (GaAs-based active layer; III-V group compound semiconductor active layer; light-emitting layer) 4 B, upper p-type The GaAs / AlGaAs multilayer DBR mirror 21 is laminated.
Here, the GaAs / InGaAs / GaAs multiple quantum well active layer 4B is formed by laminating a plurality of the GaAs / InGaAs / GaAs quantum well structures of the first embodiment described above.

A p-side electrode 22 is formed of metal on the p-type GaAs layer 21B constituting the upper DBR mirror 21, and an n-side electrode 23 is formed of metal on the n-type AlGaAs layer 20A constituting the lower DBR mirror 20. Is formed.
Here, the DBR mirrors 20 and 21 are provided so as to sandwich the active layer 4B from above and below, thereby forming a resonator structure.

  Here, in the case of the DBR mirror having the simplest complete periodic structure, the maximum reflectance of the DBR mirror is obtained at a wavelength corresponding to four times the film thickness of each layer converted to the optical distance. That is, the film thickness of each layer is obtained as a thickness corresponding to 1/4 of the desired emission wavelength divided by the refractive index of each layer. Further, the maximum value of the reflectance can be increased by increasing the number of mirror periods.

The configuration of the DBR mirrors 20 and 21 (the material of each layer, the film thickness, the number of cycles, etc.) is not limited to the above-described one, and a multilayer DBR mirror configured by a combination of other known materials is used. It can also be used. Also, DBR mirrors with other configurations can be used.
Next, a method for manufacturing the optical semiconductor element (surface emitting laser) according to the present embodiment will be described.

In the present embodiment, crystal growth is performed by, for example, UHV-CVD.
First, the p-type Ge layer 2B is grown on the p-type Si substrate 1B (see FIG. 8).
Next, on the p-type Ge layer 2B, a growth temperature (substrate temperature) of 490 ° C., supply of AsH ₃ as an As raw material and TEGa as a Ga raw material has a V / III ratio of 20 (effective V / III ratio of 2). Then, the GaAs layer 3 is grown. As a result, the first GaAs layer 3 in which part of the As site is replaced with Ga is formed on the p-type Ge layer 2B (see FIG. 8).

Next, the growth temperature is raised to, for example, 550 to 650 ° C., and the n-type GaAs layer 20B (second GaAs layer 20B is formed on the first GaAs layer 3 with a supply V / III ratio of AsH ₃ as the As material and TEGa as the Ga material. ) Grow. Then, an n-type AlGaAs layer 20A is grown on the n-type GaAs layer 20B. Such a process is repeated, and the n-type GaAs layer 20B and the n-type AlGaAs layer 20A are alternately stacked. As a result, the lower n-type GaAs / AlGaAs multilayer DBR mirror 20 is formed, in which the n-type GaAs layer 20B and the n-type AlGaAs layer 20A are alternately stacked at a film thickness of ¼ optical distance of the oscillation wavelength. (See FIG. 8).

Next, on the lower n-type GaAs / AlGaAs multilayer DBR mirror 20, for example, a GaAs layer 4x having a thickness of 10 to 30 nm and an InGaAs layer 4y having a thickness of 1 to 10 nm are alternately stacked. As a result, a GaAs / InGaAs / GaAs multiple quantum well active layer 4B is formed on the lower DBR mirror 20 (see FIG. 8).
Next, the p-type GaAs layer 21B and the p-type AlGaAs layer 21A are alternately stacked on the GaAs / InGaAs / GaAs multiple quantum well active layer 4B with a film thickness of ¼ optical distance of the oscillation wavelength. Thus, the upper p-type GaAs / AlAs multilayer DBR mirror 21 is formed on the multiple quantum well active layer 4B (see FIG. 8).

Thereafter, etching is performed by lithography, for example, until a part of the n-type AlGaAs layer 20A constituting the lower DBR mirror 20 is exposed (see FIG. 8).
Then, an n-side electrode 23 (metal electrode) is formed on the surface of the n-type AlGaAs layer 20A (see FIG. 8). Further, a p-side electrode 22 (metal electrode) is formed on the surface of the p-type GaAs layer 21B constituting the upper DBR mirror 21 (see FIG. 8).

In this way, a surface emitting laser including the GaAs-based active layer 4B above the Ge layer 2B formed on the Si substrate 1B is manufactured (see FIG. 8).
Other details are the same as those in the first embodiment described above, and thus the description thereof is omitted here.
Therefore, according to the optical semiconductor element and the manufacturing method thereof according to the present embodiment, as in the case of the first embodiment described above, the optical semiconductor including the GaAs-based active layer 4B on the Si substrate 1B via the Ge layer 2B. In the element, there is an advantage that Ge can be diffused and good device characteristics can be obtained.

The structure of the surface emitting laser is not limited to the structure of the above-described embodiment, and the present invention can be applied to other structures.
In this embodiment, the case where the present invention is applied to a surface emitting laser is described as an example. However, the present invention is not limited to this. For example, a light emitting diode (LED) or an LD (laser) is used. The present invention can also be applied to other optical semiconductor elements (light emitting elements) such as diodes.
[Others]
In each of the above-described embodiments, the case where the present invention is applied to an optical semiconductor element formed on a Si substrate (semiconductor substrate) is described as an example. However, the present invention is not limited to this. The present invention can also be applied to an optical semiconductor element formed on a (semiconductor substrate).

In each of the above-described embodiments and modifications, the optical semiconductor element (light-emitting element) is described as a single optical semiconductor element (light-emitting element). An integrated device can also be constructed by integrating on top.
Note that the present invention is not limited to the configurations described in the above-described embodiments and modifications, and various modifications can be made without departing from the spirit of the present invention.

1 Si substrate 1A, 1B p-type Si substrate 2 Ge layer 2A, 2B p-type Ge layer 3 GaAs layer in which part of As site of GaAs is replaced with Ga (first GaAs layer)
4 GaAs-based quantum well active layer (GaAs-based active layer)
4A GaAs quantum dot active layer (GaAs active layer)
4B GaAs-based multiple quantum well active layer (GaAs-based active layer)
4a GaAs layer 4b InAs quantum dot 4x GaAs layer 4y InGaAs layer 5 GaAs layer (barrier layer; second GaAs layer)
6 InGaAs layer (well layer)
7 GaAs layer (barrier layer)
10 n-type GaAs layer (contact layer; second GaAs layer)
11 n-type AlGaAs layer (cladding layer)
12 p-type AlGaAs layer (cladding layer)
13 p-type GaAs layer (contact layer)
14 p-side electrode 15 n-side electrode 20 Lower n-type GaAs / AlGaAs multilayer DBR mirror 20A n-type AlGaAs layer 20B n-type GaAs layer (second GaAs layer)
21 Upper p-type GaAs / AlGaAs multilayer DBR mirror 21A p-type AlGaAs layer 21B p-type GaAs layer 22 p-side electrode 23 n-side electrode

Claims (7)

A Ge layer;
A first GaAs layer formed on the Ge layer, wherein a part of the As site of GaAs is replaced with Ga;
An optical semiconductor device comprising: an active layer containing GaAs formed above the first GaAs layer. Comprising a Si substrate or a Ge substrate;
The optical semiconductor device according to claim 1, wherein the Ge layer is formed on the Si substrate or Ge substrate.   3. The optical semiconductor device according to claim 1, further comprising a second GaAs layer formed on the first GaAs layer.   The optical semiconductor element according to claim 1, further comprising a DBR mirror provided so as to sandwich the active layer vertically. An optical semiconductor element;
With functional elements,
The optical semiconductor element and the functional element are integrated on the same substrate;
The optical semiconductor element is:
A Ge layer;
A first GaAs layer formed on the Ge layer, wherein a part of the As site of GaAs is replaced with Ga;
An integrated device comprising: an active layer containing GaAs formed above the first GaAs layer. A first GaAs layer is formed on the Ge layer by a vapor deposition method so that an effective V / III ratio obtained by multiplying a supply V / III ratio by a decomposition efficiency is 1 or more and 2 or less,
An active layer containing GaAs is formed above the first GaAs layer.   A second GaAs layer is formed on the first GaAs layer by a vapor phase growth method with an effective V / III ratio obtained by multiplying a supply V / III ratio by a decomposition efficiency larger than 2. The manufacturing method of the optical-semiconductor element of Claim 6.

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