JP2761264B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for manufacturing a semiconductor device, in particular, an HBT, which aims to suppress abnormal diffusion of Be in a semiconductor device having an epitaxial layer made of a compound semiconductor material containing Be at a high concentration. Formed on the crystal layer with lattice matching, GaAlAs and InGaAl
In a method of manufacturing a semiconductor device comprising a III-V compound semiconductor material selected from the group consisting of As and having a p-type doped epitaxial layer by adding Be, Be is added to the epitaxial layer by about 5 × 10 ¹⁹ atoms. / cm ^{3 to} about 5 × 10
Adding to a concentration level of ²⁰ atoms / cm ³ , and adding 0.5% of In to the group III element in the semiconductor material in the epitaxial layer.
And a step of growing an n-type collector layer on the crystal layer and a step of adding GaAlAs.
And growing a base layer made of a III-V compound semiconductor material selected from the group consisting of InGaAlAs and the n-type collector layer on the n-type collector layer. Doping the base layer into p-type by adding to a concentration level of ¹⁹ atoms / cm ³ to 5 × 10 ²⁰ atoms / cm ³ , and adding In to the group III element contained in the base layer. A step of adding 0.5 mol% to 8 mol%, and a step of growing an n-type emitter layer on the base layer, further formed on the crystal layer with lattice matching, and comprising GaAlAs and InGaAl
In a method of manufacturing a semiconductor device comprising a III-V compound semiconductor material selected from the group consisting of As and having an epitaxial layer doped p-type by adding Be, a step of adding Be to a predetermined concentration level; Is added to Be in a substantially equal amount.

[Industrial applications]

The present invention relates to a method for manufacturing a semiconductor device, in particular, a heterojunction bipolar transistor (HBT).

HBT using III-V compound semiconductor material such as GaAs
Is characterized by high-speed operation. This is mainly due to the high electron mobility in the group III-V compound constituting the transistor. Further, the fact that a material having a large band gap can be used for the emitter also contributes to the improvement of the operation speed.

In such HBTs or bipolar transistors in general, it is desirable that the base be formed as thin as possible so that the passage time of the electrons decreases and the operation speed of the transistor improves. However, if the thickness of the base is too thin, the base resistance increases and the operating speed of the transistor decreases. In order to make the base thinner without increasing the base resistance, it is desirable to make the doping concentration of the base as high as possible, for example, about 1 × 10 ²⁰ cm ⁻³ or more.

On the other hand, it is known that the operating speed of the HBT is further improved by forming an electric field in the base so that electrons passing through the base are accelerated by the electric field. Such an electric field is obtained by imparting a composition gradient to the semiconductor material constituting the base so that a large band gap is formed on the base in contact with the emitter and a small band gap is formed on the base in contact with the collector. For this purpose, the composition x is changed from 0 to, for example, 0.1 using GaAlAs whose composition is represented by Ga _1-x Al _x As as a base.
In the above system, there is substantially no change in the lattice constant, and the problem of lattice mismatch can be avoided.

[Problems to be solved by the invention]

In an npn-type HBT formed on a GaAs substrate and having p-type doped GaAs as a base, Be is generally used as a base dopant. By the way, it is known that the diffusion coefficient of Be in GaAs increases to 1000 times to 10,000 times when the composition of Be increases to a level of about 4 × 10 ¹⁹ cm ⁻³ or more ( Pao, Weishy et al., Journal of Applied Physics 60 , 1986, p. 201; Pao, YC, J. Ap
pl · Phys · 60, 1986, P201). It is also known that such an increase in the diffusion coefficient of Be is more remarkable in the GaAlAs system (Miller, DJ, Journal of Applied Physics 57 , 1816, 1985; Miller, DJ).
・, J. Appl. Phys. 57 , 1985, P1816). In other words, Be tends to diffuse into adjacent collectors or emitters during the manufacturing process, which may change the conductivity type of the emitters and collectors, or destroy the bipolar structure of the transistor. For growth of GaAlAs
A high temperature of about 600 ° C. or higher is required, and the problem that Be diffuses to the collector and the emitter becomes particularly serious in the case of an HBT using GaAlAs to realize a graded base. For this reason, in the conventional HBT, the base was made sufficiently thin and the composition gradient was given, so that the high-speed performance of the HBT could not be fully exhibited.

A similar problem is that the HBT has a structure in which the base of InGaAlAs is sandwiched between the collector and the emitter of InGaAs on the InP substrate.
Also occurs in That is, Be is approximately 1 × in InGaAlAs.
When doped in an amount exceeding 10 ²⁰ cm ^-3 , the diffusion coefficient of Be rapidly increases.

On the other hand, HBT doped Be with a high concentration in the base by Wang et al.
Are known (One, Casey, Asbeck, P
M, Zhang, M.F., Sullivan, G.J. and Miller, D.L.E.I.E.I.E.Electron Device Letters IDL-8,9,1987
Sep. 383-385; Wang, K.C., Asbeck, PM, Chang, M.
F, Sullivan, GJ, and Miller, DL, IEEE Electron
Device Letters, EDL-8, No.9, September 1987, PP.383-
385). In this example, the problem of anomalous diffusion of Be
This is avoided by using InGaAs not containing l and forming the base at a low temperature of about 500 ° C. or less. However, in this known device, a composition gradient cannot be formed in the base, so that the operating speed is limited. On the other hand, if an element other than Al is added to the above system to form a composition gradient, an unacceptable lattice mismatch with the collector or the emitter will occur.

The present invention has been made in view of the above points, and has as its object to suppress abnormal diffusion of Be in a semiconductor device having an epitaxial layer made of a compound semiconductor material containing Be at a high concentration.

[Means for solving the problem]

The present invention solves the above problems by forming a lattice-matched GaAlAs and InGaAs layer on a crystal layer.
In a method for manufacturing a semiconductor device comprising a III-V compound semiconductor material selected from the group consisting of: a p-type doped epitaxial layer by adding Be, Be is added to the epitaxial layer at 5 × 10 ¹⁹ atoms / cm 3. ³ to 5 × 10 ²⁰ atoms
/ cm ^{3 at} a concentration level of 0.5 mol% with respect to the group III element in the semiconductor material.
A step of growing an n-type collector layer on the crystal layer;
Growing a base layer made of a group III-V compound semiconductor material selected from the group consisting of As and InGaAlAs on the n-type collector layer, wherein the base layer contains In as a base layer. Adding 0.5 mol% to 8 mol% to the group III element contained therein, and adding about 5 × 10 ¹⁹ Be to the base layer.
Doping the base layer p-type by adding a concentration level of atoms / cm ^{3 to} about 5 × 10 ²⁰ atoms / cm ³ , and growing an n-type emitter layer on the base layer. GaAlAs and InGaAl are formed by a manufacturing method and further lattice-matched on the crystal layer.
In a method of manufacturing a semiconductor device comprising a III-V compound semiconductor material selected from the group consisting of As and having an epitaxial layer doped p-type by adding Be, a step of adding Be to a predetermined concentration level; Is added to Be in a substantially equal amount.

[Action]

According to the present invention, the strain caused by adding Be having a small atomic radius (1.06 °) to the crystal structure of a group III-V compound semiconductor material is reduced by adding In having a large atomic radius (1.44 °). Compensated. As a result, the energy instability of Be caused by the strain energy due to the lattice deformation and the declining energy barrier of diffusion associated therewith are eliminated, and the problem of anomalous diffusion of Be is solved. Be and In are randomly distributed in the crystal structure where the group III element enters, and the strain in the crystal is uniformly relaxed. As a result of solving the problem of anomalous diffusion of Be, it becomes possible to form a semiconductor device such as HBT without a risk that a semiconductor layer adjacent to the epitaxial layer is erroneously doped or a device structure is destroyed. .

Hereinafter, the principle of the present invention will be described with reference to FIGS. 1 (A) and 1 (B).

FIG. 1A shows a schematic structure of GaAs. In the figure, Ga
Atom 2 and As atom 4 form a zinc-blende fcc structure,
The a atom goes into the four-coordinate group III element, while the As atom also goes into the four-coordinate group V element. If this is GaAlAs,
Al replaces part of Ga.

When a substantial amount of Be is added to the structure of FIG. 1A, the Be atoms replace a part of the Ga atoms 2 as shown in FIG. 1B. As a result, especially when the concentration of Be was about 5 × 10 ¹⁹ cm ⁻³
When it reaches ５5 × 10 ²⁰ , the crystal structure is distorted or deformed due to the substantially smaller atomic radius of Be compared to Ga or Al.

Table I below summarizes the atomic radii of Be and the Group III and Group V elements involved in the HBT of the present invention.

Table I Table 1.0 showing the atomic radii of typical group III and V elements compared to the atomic radii of Be used for doping of group III-V compounds. Be 1.06 Al 1.26 Ga 1.26 In 1.44 As 1.18 In the present invention, anomalous diffusion of Be in a system of GaAlAs or InGaAlAs causes In to 0.5 to 8 mol% of the group III element in the system.
The addition was found to be suppressed. Ie
By adding In atom 3 at the same time as Be atom 1, the strain in the crystal structure is relaxed as shown in FIG. 1 (B). It is considered that such relaxation of the strain in the crystal relatively lowers the energy of Be in the structure, and conversely, the barrier energy of diffusion relatively increases. as a result
It is considered that the problem of anomalous diffusion of Be into the adjacent semiconductor layer is solved.

FIGS. 2A and 2B show the results of adding In according to the present invention.
The configuration of an experimental sample for verifying the effect of eliminating the anomalous diffusion of Be is shown.

FIG. 2 (A) shows a sample prepared by the conventional method, that is, without adding In at the same time as adding Be.
A GaAs buffer layer 32 epitaxially grown to a thickness of 500 mm on the (100) face of the GaAs substrate 31;
GaAlAs layer 33 having composition Ga _0.9 Al _0.1 As grown at 00 °
And a GaAlAs layer 34 formed on the GaAlAs layer 33 and having the same p-type doped composition as Ga _0.9 Al _0.1 As and having a thickness of 1000
34 and another composition of the same composition Ga _0.9 Al _0.1 As
It is composed of a GaAlAs layer 35. The layer 34 is thicker than a typical HBT base in order to examine the diffusion of Be in detail. In the drawing, the vertical axis represents the Al concentration in the layers 31 to 35.

FIG. 2 (B) shows an experimental sample corresponding to the present invention. In the figure, portions corresponding to those in FIG. 1 (A) are denoted by the same reference numerals, and description thereof is omitted.

In the sample shown in FIG. 2 (B), after the buffer layer 32 was epitaxially grown at 500 °, GaAl having a composition of Ga _0.9 Al _0.1 As was used.
The As layer 33a is grown to a thickness of 2000 mm. Next, the composition Ga _0.9 Al
A lower boundary layer 35 composed of _0.1 As and In
成長 is grown, and a p-type GaAlAs layer 37 is further formed to a thickness of 1000 °. In the layer 37, In is added at the same time as Be is added. Further, a GaAlAs upper boundary layer 39 having a composition obtained by adding In to the composition Ga _0.9 Al _0.1 As is grown to a thickness of 100 mm on the p-type layer 37, and another GaAlAs having a composition of Ga _0.9 Al _0.1 As is further formed thereon.
Layer 35a is grown to a thickness of 3000 mm. The concentration level of In with respect to the total amount of Ga and Al is the same in the layers 36 to 38. Further, many samples having the structure shown in FIG. 2 (B) were prepared by changing the concentration of In. In FIG. 2 (B), the vertical axis indicates the Al concentration as in FIG. 2 (A).

In each sample, the semiconductor layer was grown by MBE at a temperature of 600 ° C. at a growth rate of 1 μm / hour. During the growth, the vapor pressure of As is controlled to 4 × 10 ⁻⁵ Torr, and the temperature of the cell holding the Al and Ga source materials is controlled by the Al in the semiconductor layer formed.
And the ratio of Ga was controlled to be maintained at 1: 9. Furthermore, B
The temperature of the cell holding the source material of e and In was controlled so that the concentration level of these elements became a predetermined value. Thus, during the growth of the layer 37, Be alone or together with In
As is taken into the group III element of As.

FIGS. 3 (A) and (B) show test results for the sample of FIG. 2 (A). The evaluation of the test results was performed by obtaining the composition profile of Be from the surface of the layer 35 to the bottom surface of the layer 33 by SIMS. 3 (A) shows the Be layer 34.
^Shows the case where it was introduced at a concentration level of 3 × 10 ¹⁹ cm ⁻³ ,
On the other hand, FIG. 3B shows the case where Be is introduced into the layer 34 at a concentration level of 7 × 10 ¹⁹ cm ⁻³ . Hereinafter, the width of the layer containing Be is defined as the layer thickness at a concentration one digit lower than the maximum concentration of Be.

As is clear from FIG. 3 (A), when the doping level of Be is 3 × 10 ¹⁹ cm ⁻³ or less, the thickness of the portion containing Be in the sample is about 1200 ° corresponding to the design value of the base layer 34. Within the range. No diffusion of Be beyond the base layer 34 is observed. On the other hand, when the concentration of Be is increased to 1 × 10 ¹⁹ cm ^−3, it is clear from FIG. 3 (B) that the thickness of the Be-containing portion in the sample has increased to about 1500 °. In other words, this result is consistent with the report in
This indicates that substantial diffusion of Be from the gas has occurred.

On the other hand, FIGS. 4 (A) to 4 (C) show the results of FIG. 2 (B) with the Be doping concentration fixed at 7 × 10 ¹⁹ cm ^−3.
Shows the results when the concentration of was variously changed. The evaluation was also performed by SIMS.

Referring to FIG. 4 (A), in this experiment, the In concentration level was 1 × 10 ²¹ cm ⁻³ while the Be concentration level was 7 × 10 ¹⁹ cm ⁻³ .
However, as in FIG. 3 (B), an expansion of the Be-containing region in the sample to about 1800 ° was observed. In other words, in this case, the same abnormal diffusion of Be occurs as in the previous case.

On the other hand, in the example of FIG. 4 (B), the In concentration level is 1 × 10 ¹⁹
cm ^-3 and being, but the thickness of the region containing the sample Be it is understood that Be concentration level of the layer 37 is within the range of about 1200Å even 7 × 10 ¹⁹ cm ^-3. In other words, the extraordinary diffusion of Be is GaAl
It can be seen that when the amount of In in the As layer 37 is set in this manner, it is effectively suppressed.

Further reduce the amount of In to 5 × the detection limit of SIMS
^When the thickness is reduced to ¹⁹ cm ^-3 or less, as shown in FIG.
It expands to 00Å. In this case, it is considered that the suppression of the abnormal diffusion of Be is not effective because the concentration level of In is too low.

A similar tendency is observed in GaAs, InGaAs or InGaAlAs systems. In general, an abnormal increase in the diffusion coefficient of Be
It has been found that it can be suppressed by adding it in the form of the formula In _y (III) _1-y (V) simultaneously with the Be doping. Where (III) is III
(V) represents a group V element, and y = 0 represents a virtual composition without Be doping. The composition y is generally proportional to the amount of Be added by doping. By adding In in this manner, the composition ratio between two or more Group III elements, which is usually set so as to achieve lattice matching with the adjacent layer, is maintained. For example, In is introduced according to the formula _{In y (Ga 1-x Al} x) 1-y As with respect to Ga _1-x Al _x As. Clearly, the ratio of Al to Ga does not change with the addition of In. When In is added to a system already containing In, for example, In _x Ga _1-x As, the composition after the addition of In is represented by In _y (In _x Ga _1-x ) _1-y As. As described above, the value y is determined by the concentration level of Be. When Be is doped at a level of 5 × 10 ^{19 to} 5 × 10 ²⁰ cm ⁻³ , the value of y is set to 0.005 to 0.0 to suppress the abnormal diffusion of Be.
It is preferably set to 8.

FIG. 5 shows a case where the In concentration level is variously changed by the thickness of the Be-containing region formed in the sample of FIG. 2 (B). As in the original experiment, the concentration of Be was 7 × 10 ¹⁹
cm ^-3 is set. As is clear from this figure, the thickness of the Be-containing region is minimized when the composition of the InAs component is in the range of about 0.5 mol% to about 8 mol%.

The above results clearly show that anomalous diffusion of Be is suppressed by adding In to the system at the same time. The reason for this is that the strain induced by Be in the crystal structure
It is understood as a result of the compensation by addition. That is, it is considered that the energy of Be is stabilized against the energy barrier of Be diffusion as a result of the relaxation of the lattice strain. According to this theory, the following relational expression is expected to hold.

(V _Ga −V _Be ) N _Be = (V _In −V _Ga ) N _In where V _Ga , V _Be and V _In are the atomic volumes of Ga, Be and In, respectively, and N _Be and N _In are Be And the number of atoms of In.
In other words, it should be possible to suppress anomalous diffusion of Be by doping In with substantially the same amount of In as In. Fig. 4 (A)
(C) and the results in FIG. 5 support this prediction.
That is, if the amount of In is too small as in the case of FIG. 4 (C), strain in the crystal lattice remains, so that abnormal Be diffusion cannot be suppressed.
As in the case of FIG. 7A, strain is induced by In in the crystal lattice, and the abnormal diffusion of Be does not disappear. Thus, the appearance of the optimum composition range of In corresponding to a constant Be concentration level as shown in FIG. 5 can be reasonably explained by this theory. It is clear that the suppression of anomalous diffusion of Be by simultaneous doping with In is not limited to the GaAlAs system, but can be similarly applied to other systems.

〔Example〕

Next, the HBT manufactured by the method of the present invention will be described. FIG. 6 shows an HBT according to an embodiment of the present invention, wherein n ^{+ type} G
A collector buffer layer 13 made of aAs and an n-type GaAs collector layer 14 are sequentially epitaxially grown on the (100) plane of the semi-insulating GaAs substrate 11. Collector buffer layer 13
Has a thickness of 5000 ° and a donor concentration level of 3 × 10 ¹⁸ cm ⁻³ , whereas the collector layer 14 has a thickness of 3000 ° and a donor concentration level of 5 × 10 ¹⁶ cm ⁻³ .

On the GaAs collector layer 14, an InGaAlAs base layer 16 doped with P ^{+ in} Be and tuned so that the composition is lattice-matched to the lower collector layer 14 is, for example, about 1000 ° thick and shown in FIG. Epitaxial growth is performed with such an Al composition gradient. Be doping is typically about 1 × 10
Performed to a concentration level of ²⁰ cm ^-3 . In addition, base layer 16
An n-type GaAlAs emitter layer 20 and an n ⁺ -type emitter cap layer 24 are formed thereon with an Al composition gradient shown in FIG.
The composition of the base layer 16 is set to such a value as to lattice match with the collector layer 14 in a virtual state in which In and Be are not added. Be
When only base is doped to 5 × 10 ^{19 to} 5 × 10 ²⁰ cm ⁻³ to reduce the spreading resistance of the base, the lattice matching is lost due to the small atomic radius of Be.
According to the formula In _y (Ga _1-x Al _x ) _1-y As, where y is 0.005 to
Loss of lattice matching is obtained again by addition in the range of 0.08. The composition x of Al is represented by (1-x)
The value of Ga at the interface with collector layer 14 is 0.0
To a value of 0.1 at the interface with the emitter layer 20 independently of the composition parameter y. Therefore, it is possible to form an electric field for accelerating electrons traversing the base in exactly the same manner as without In doping.

The n-type emitter layer 20 has a thickness of about 300.degree.
× 10 ¹⁷ cm ^-3 , the first in which the Al composition changes from 0.1 to 0.3
Layer 21 with a thickness of about 900 mm and a donor concentration of about 5 × 10
^A second layer 22 of ¹⁷ cm ^-3 and a constant Al composition of 0.3, a thickness of about 300 °, a donor concentration of about 5 × 10 ¹⁷ cm ^-3 and an Al composition of 0.3 to 0.3 cm ³ as shown in FIG. Third layer 2 reduced to zero
Consists of three. Such a compositional gradient of Al makes the band structure continuous in a cross section passing through the collector, the base and the emitter, and makes it possible to remove spikes and notches from the band structure.

The n ^{+ type} cap layer 24 has a thickness of about 1500 Å and a donor concentration of about 5
× 10 ¹⁸ cm ^-3 . An emitter electrode 25 is provided on the cap layer 24. Similarly, a base electrode 26 is provided on the base layer 14, and a collector electrode 27 is provided on the collector buffer layer 13.

The layers 12 to 24, in particular, the base layer 16 are preferably formed by the MBE method already described with reference to the preparation of the sample in FIG. 2B, or by MOCVD which can realize almost ideal stoichiometry. The epitaxial growth of the Al-containing layers 16 and 20 is performed at a temperature in the range of 550-680 ° C, preferably at a temperature of 600 ° C or higher. By adding In to the base layer 16 together with Be, diffusion of Be into the adjacent emitter layer 20 or collector layer 14 is effective even when the layers 16 and 20 are formed at such a relatively high temperature range. And the collapse of the HBT structure can be prevented. Moreover, such an HBT structure maintains a preferable composition gradient for realizing high-speed operation.

Next, the second embodiment of the HBT according to the present invention will be described with reference to FIG.
An embodiment will be described. In this embodiment, HBT is a semi-insulating InP substrate.
Formed on 41. Referring to FIG. 8, an undoped InAlAs buffer layer 43 is epitaxially grown on a substrate 41 in a lattice-matched state to a thickness of about 3000 °, and an n ^{+ -type} InGaAs collector contact layer 45 is formed on the buffer layer 43. It is grown at a donor concentration level of 2 × 10 ¹⁹ cm ⁻³ and a thickness of 5000 °. Further, an n-type InGaAs collector layer 47 is formed on the collector contact layer 45 at a donor concentration level of 3 × 10 ¹⁶ cm ^-3 and 5000
エ ピ タ キ シ ャ ル is epitaxially grown. InGaAs layer 45
And 47 have a composition of In _0.53 G so as to match the lattice of the InP substrate 41.
a _0.47 As, and the composition of the InAlAs buffer layer is In _0.52 A
l _0.48 As. On the collector structure thus formed, an InGaAlAs base layer 49 is epitaxially grown to a thickness of about 1000 °. This base layer 49 has a Be of about 1 × 10
It is doped p-type by adding it to a concentration level of ²⁰ cm ^-3 . Further, the base layer 49 has a composition gradient in which the Al composition changes from 0 to 0.2 later from the lower end to the upper end. In the base layer 49, simultaneously with the Be doping, the In concentration is also increased from 0.53 to a value commensurate with the Be concentration according to the above relationship. When the Be concentration is set in the range of 5 × 10 ^{19 to} 5 × 10 ²⁰ cm ⁻³ , In is y = 0.008 to 0.05 according to the formula Iny [In _0.53 (Ga _1−x Al _x ) _0.47 ] _1−y As Is increased by an amount corresponding to the range of Further, the value of x is from 0 to 0 corresponding to the Al composition gradient.
Can be changed to 0.2.

On the base layer 49, a first emitter layer 51 made of n-type InGaAlAs having a composition of In _0.53 (Ga _{1 -x} Al _x ) _0.47 As has a parameter x of 0.1 from the bottom to the top.
Grow while changing from 2 to 1. This first
The emitter layer 51 has a thickness of about 300 mm, and the InAlA
A second emitter layer 53 of s is formed with a thickness of about 2000 °. In either of the first and second emitter layers 51 and 53, the donor concentration level is fixed at about 2 × 10 ¹⁷ cm ⁻³ .

Furthermore, it is doped n-type and the donor concentration level is about 2 ×
The second cap layer 55 made of InGaAlAs of 10 ¹⁹ cm ^-3
Is grown to a thickness of about 700 ° on the emitter layer 53 while changing its composition from 100% InAlAs on the bottom surface to 100% InGaAs on the top surface. Further, a second cap layer 57 made of InGaAs is grown on the first cap layer 55 to a thickness of about 500 °. This second cap layer 57 has a thickness of about 1 × 10 ¹⁹ cm ^−3.
At a donor concentration level of Emitter layer 51 and
As a result of the 53 composition gradients, unwanted spikes and notches can be removed from the band structure. Finally, an emitter electrode 61 made of an Au / Ge alloy and a base electrode 6 made of an Au / Zn alloy
2 and a collector electrode 63 made of an Au / Ge alloy are formed on the emitter cap layer 57, the base layer 49, and the collector contact layer 45, respectively, to complete the HBT of this embodiment.

As in the previous embodiment, the growth of layers 45 to 57 is performed by MBE or MOC.
This is done at a temperature of 600 ° C or more by VD. By doping Be and In into the base layer 49 at the same time, diffusion of Be into the adjacent layer is effectively suppressed despite the high growth temperature of the base layer. As a result, an HBT having an extremely high operating speed can be obtained by using a thin and low-resistance base and simultaneously providing a composition gradient in the base and the emitter.
In addition, the reproducibility of the HBT structure is improved by suppressing the abnormal diffusion of Be.

Hereinafter, the present invention has been described with reference to examples. However, the present invention can be variously modified in accordance with the gist thereof, and these are not excluded from the present invention.

〔The invention's effect〕

According to the present invention, an HBT using a III-V compound semiconductor
By doping In at the same time as Be doping, strain of the lattice can be reduced and abnormal diffusion of Be can be prevented. This requires a growth process at a high temperature
Even in an HBT having an Al composition gradient as a base, a large amount of Be can be doped into the base, and accordingly, the thickness of the base can be reduced without increasing the base spreading resistance. As a result, it becomes possible to form an HBT having an extremely high operation speed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention; FIGS. 2 (A) and (B) are diagrams showing the structure of a sample used in a comparative experiment of the method of the present invention and a conventional example; FIGS. FIG. 4B shows the results of an evaluation experiment obtained on a sample prepared by the conventional method; FIGS. 4A, 4B, and 4C show the evaluation obtained on the sample prepared by the method of the present invention; FIG. 5 is a diagram showing experimental results; FIG. 5 is another diagram showing the results of evaluation experiments obtained on the sample prepared by the method of the present invention; FIG. 6 is a diagram showing the configuration of an embodiment of the HBT prepared by the method of the present invention; FIG. 7 is a diagram showing an Al composition profile in the HBT of FIG. 6; FIG. 8 is a diagram showing a configuration of another embodiment of the HBT produced by the method of the present invention. In the figure, 1 is Be atom, 2 is Ga atom, 3 is In atom, 4 is As atom, 11 is GaAs substrate, 12 is GaAs buffer layer, 13 is GaAs collector contact layer, 14 is GaAs collector layer, 16 is GaAlAs Base layer, 20 is a GaAlAs emitter layer, 21 is an emitter first layer, 22 is an emitter second layer, 23 is an emitter third layer, 24 is a GaAs emitter cap layer, 25 is an emitter electrode, 26 is a base electrode, 27 is a collector Electrodes, 31 is a GaAs substrate, 32 is a GaAs buffer layer, 33 is a GaAlAs layer, 34 is a Be-doped GaAlAs layer, 35 is a GaAlAs layer, 33a and 35a are GaAlAs layers, 36 is an In-doped GaAlAs boundary layer, 37 is In, Be Doped GaAlAs layer, 38 is an In-doped GaAlAs boundary layer, 41 is an InP substrate, 43 is an InAlAs buffer layer, 45 is an InGaAs collector contact layer, 47 is an InGaAs collector layer, 49 is an InGaAlAs base layer, 51 is an InGaAlAs emitter first layer, 53 is the second layer of the InGaAlAs emitter, 55 is the third layer of the InGaAlAs emitter, 57 is the InGaAs emitter A cap layer, 61 indicates an emitter electrode, 62 indicates a base electrode, and 63 indicates a collector electrode.

──────────────────────────────────────────────────続 き Continued on the front page (58) Investigated field (Int.Cl. ⁶ , DB name) H01L 21 / 203,21 / 205,21 / 31,21 / 328,2 1 / 33,21 / 331,21 / 363,2 1 / 365,21 / 469,21 / 86 H01L 29/68-29/739

Claims (3)

(57) [Claims] 1. A group III-V compound semiconductor formed on a crystal layer (11-14, 31-36, 41-47) in lattice-matching and selected from the group consisting of gallium aluminum arsenide and indium gallium aluminum arsenide. A method of manufacturing a semiconductor device having an epitaxial layer made of a material and doped in a p-type by adding beryllium, wherein beryllium is contained in the epitaxial layer in an amount of 5 × 10 ¹⁹ atoms / cm ³ to 5 × 10 ²⁰ atoms / cm ^3.
And a step of adding 0.5% to 8% by mole of indium to the epitaxial layer with respect to the group III element in the semiconductor material. 2. The method according to claim 1, further comprising the steps of: growing an n-type collector layer (14, 47) on the crystal layer (11-13, 41-45); Growing a base layer (16,49) of a group V compound semiconductor material on the n-type collector layer, wherein the base layer contains beryllium in an amount of about 5 × 10 ¹⁹ atoms. / c
doping the base layer into p-type by adding to a concentration level of m ^{3 to} about 5 × 10 ²⁰ atoms / cm ³ , wherein indium is contained in the base layer in an amount of 0.5 mol based on the group III element contained in the base layer. % To 8 mol%, and growing an n-type emitter layer (20, 51 to 55) on the base layer. 3. A group III-V compound semiconductor formed on the crystal layers (11-14, 31-36, 41-47) in lattice-matching and selected from the group consisting of gallium aluminum arsenide and indium gallium aluminum arsenide. A method of manufacturing a semiconductor device comprising a material and having an epitaxial layer doped with p-type by adding beryllium, comprising: adding beryllium to a predetermined concentration level; and adding substantially equal amounts of indium to beryllium. The manufacturing method characterized by the above-mentioned.