JPH03148112A - Manufacture of compound semiconductor - Google Patents

Abstract

PURPOSE:To reduce a base resistance even if the width of the base is narrowed by adding specific mol% of Sb atoms to As atoms of group V forming GaAlAs or InGaAlAs together with Be atoms of specific atoms/cm<3> during a growing step CONSTITUTION:0.5-10mol% of Sb atoms 5 are added to As of V group atoms for forming GaAlAs or InGaAlAs together with Be atoms 1 of 5X10<19>-5X10<20> atoms/cm<3> during a growing step. When the Sb having large atomic radius is doped, the Sb is introduced to the position of V group element at random to alleviate a distortion generated by the Be having small atomic radius. Accordingly, the Be atoms 1 are stood still in a lower energy state, and abnormal increase of a diffusion coefficient is reduced. Thus, even if an epitaxial layer having different conductivity type from that is adjacently grown, the Be is diffused to eliminate the damage of a predetermined impurity profile. In this manner, a base resistance can be reduced by a narrow base width.

Description

[Detailed Description of the Invention] [Summary] A method for manufacturing a compound semiconductor including a step of lengthening a p-type epitaxial layer doped with impurities at a high concentration, GaAlAs or InGaAlA containing a high concentration of Be.
The purpose of the present invention is to provide a method for manufacturing a compound semiconductor that can lengthen the epitaxial layer of S and suppress an abnormal increase in the diffusion coefficient of Be. -polymerized GaA1As or 1.
In a compound semiconductor manufacturing method including a step of growing a p-type epitaxial layer of nGaAj2As, during this growth step, 5×1020 to 5×1020 atoms/cI11
This GaAfAs or I n
0.5 to 10 mol % of Sb atoms are added to As, which is a group II atom constituting GaAj2As.

Configure it as follows.

[Industrial application field]

The present invention relates to a method for manufacturing a compound semiconductor, and particularly to a method for manufacturing a compound semiconductor including a step of growing a p-type epitaxial layer doped with impurities at a high concentration.

[Conventional technology]

In recent years, various semiconductor devices using group Ⅰ-group V compound semiconductors have been actively developed, and various properties are desired for the group Ⅰ-group V compound semiconductors depending on their uses. One example of this is that extremely low resistance may be desired.

Usually, to reduce the resistivity of a semiconductor, an appropriate amount of atoms that emit electrons or holes are added as impurities in the semiconductor.

In order to improve the high frequency characteristics of a heterojunction bipolar transistor (HBT), it is required to reduce its resistance without increasing its base width. There is also a report that the operating characteristics are improved by making the base region a graded base with a composition gradient (T.

l5hibashi et al IEEE Elec
tron Device Lett.

EDL-8, (19B?) 194). npn-GaA/! with GaAs as a substrate! In the case of an As heterojunction bipolar transistor, in order to satisfy the above two characteristics improvement conditions, Ga+-x Alw As (x=0 to 0.
1) A large amount of p-type impurity (approximately 1x
It is necessary to lower the base resistance by adding Be) of the order of 113 io'' atoms/cI.

By the way, when Be is added to GaAs at a high concentration, the Be
It is known that the diffusion coefficient of
ao et al. J. Appl. Phys.

60 (1986) 201), GaA/! It is also known that Be diffusion occurs more easily in As than in GaAs (D, LoMill
er etal, J, Appl, Phys, 5
7 (1985) 1816).

In addition, I no, 5iGao, ny using InP as a substrate
A S / I no, st A 1 o, 411
In the case of an npn-heterojunction bipolar transistor made of A S, Be is added in an amount of about lXl0'' atoms/c113 to lower the base resistance, but in this case too, B
A similar phenomenon occurs in which the diffusion coefficient of e increases by an order of magnitude.

[Problem to be solved by the invention]

In this way, p4 conductivity type Ga with a large amount of Be added
In Aj2As and InGaAffiAs, since Be has an extremely large diffusion coefficient, such p
When a region made of a semiconductor of ``'' conductivity type is placed adjacent to an N region of n'' type, n-type, or p-type conductivity, Be easily diffuses into the adjacent region due to an abnormally large diffusion coefficient. , there was a great risk of changing the conductivity type of the adjacent region.

If the conductivity type of the adjacent region is changed, in the case of a heterojunction bipolar transistor, the original HBT structure including the heterojunction and pn junction will be destroyed.

The purpose of the present invention is to eliminate this drawback, and to
GaAffiAs or InGaAj! containing a high concentration of
An object of the present invention is to provide a method for manufacturing a compound semiconductor that can control the length of an As epitaxial layer and suppress an abnormal increase in the Be diffusion coefficient.

Means for Solving Problem C] The above object is to provide GaAj! which is lattice-matched to the underlying crystal and doped with Be! As or I n
G a A j! In a method for manufacturing a compound semiconductor including a step of growing a p-type epitaxial layer of As,
During this growth process, 5×1019 to 5×102° atoms/c
Together with the Be atom (1) of I113, this GaAfAs
or 0.5 to 10 mol% of Sb atoms (5) with respect to As, which is a group II atom constituting InGaAffiAs
This is achieved by a compound semiconductor manufacturing method that adds .

C Effect] A diagram illustrating the principle of the present invention is shown in FIG. In the figure, l is a Be atom, which acts as a p-type impurity in the ■-■ group compound semiconductor. 2 is Ga or Ai! , is an atom,
It is a group ■ element that is a constituent element of a ■-■ group compound semiconductor. , 3 is an In atom, which is also a group Ⅰ element that is a constituent element of the m-v group compound semiconductor. 4 is an As atom, which is a group V element that is a constituent element of the ■-V group metal semiconductor. 5 is an Sb atom, which is a group V element that is a constituent element of the ■-■ group compound semiconductor.

GaAlAs contains Al2 and Ga as group ■ elements,
It is a ■-V group compound semiconductor containing As as a V group element. InGaAj! As is a ■-v group compound semiconductor that further contains In as a group ■ element.

Be, which is a dopant, is an alkaline earth metal of Group ■ of the periodic table, and when doped into a ■-V group compound semiconductor, ■
It randomly enters the position of group elements and supplies one hole per Be atom.

Be in GaAl2AS or InGaAlAs
When doped with a high concentration, the atomic radius of Be becomes In,G
Since a is smaller than the atomic radius of Al2, distortion occurs in the crystal.

The bonding mode of Be, which enters the position of the group (2) element as a substitution type, is isotropic (c-cubic symmetry). The atomic radius in a regular tetrahedral bond configuration is known as follows.

Be 1.06 people A/2 1.26 people Ga 1.26 people In 1.44 people As 1.18 people Sb 1.36 people The effect of SbO counter doping on Be doping is considered as follows.

When strain occurs due to Be doping, Be atoms are induced by the strain and enter a high energy state. Therefore, the barrier energy for movement by diffusion becomes relatively low, and diffusion easily occurs. This is the cause of the abnormal increase in the diffusion coefficient.

Therefore, when Sb, which has a large atomic radius, is doped, Sb randomly enters the position of the group III element and alleviates the strain caused by the small atomic radius, so the Be atoms settle into a lower energy state and have a diffusion coefficient. The abnormal increase in will be reduced.

Therefore, even if an epitaxial layer having a different conductivity type is grown adjacently, Be will not be diffused and the intended impurity profile will not be destroyed.

The counter-doping amount of Sb required when doping Al2GaAs with Be can be determined as follows.

AI! , Replacement of Ga with Be causes a decrease in volume, which causes distortion.
The volume decrease can be compensated for by the volume increase of Sb, which has a large atomic radius, and the following formula holds true.

(VGa-vBe)NBe-(vSb-vAs)NSb
However, vG8, vBe, vSb”As are Ga and Be, respectively.
.

It is the volume of Sb and ^S atoms, and NBe and NSb are the numbers of Be atoms and Sb atoms, respectively. In the case of the present invention N ξ
0.9 N88, and it is judged that it is effective to counter-dope Sb in an amount comparable to that of Sb when doping Be.

〔Example〕

Hereinafter, two embodiments according to the present invention will be described with reference to the drawings, taking as an example the case of manufacturing a hetero bipolar transistor.

Refer to Figure 2. GaAs is deposited on a semi-insulating (100) plane GaAs substrate
The epitaxial fiber layer 12 has a thickness of 5.0
00 people, n-type Ga with donor concentration 3X10''(4)-3
As collector buffer layer 13 and thickness 3.0OOA,
n-type GaAs with donor concentration 5 x 10'bc, -,
A collector layer 14 is epitaxially grown.

A P-type GaAlAs space layer 15 lattice-matched to GaAs is placed on the n-type GaAs collector layer 14 with a thickness of about 1.000λ.
Thick epitaxial growth is performed, and further n-type GaA is grown on top of the epitaxial growth.
A lAs vine layer 16 and an n+ type GaAs vine cap layer 17 are epitaxially grown. p1 type GaAf
The composition of the group ■ elements in the fiAs base layer 15 is An! , Ga
When expressed as +-, the A42 composition is approximately 0.1 on the upper surface of the base layer 15 and gradually decreases to O toward the collector layer 14. In order to lower the resistance, the base layer 15 contains 5×10'9 Be as an acceptor.
In order to alleviate the strain in the base layer caused by doping within the range of ~5×1020CI-', Sb according to the present invention is doped with GaAlAs in a range corresponding to the doping amount of Be.
Or InGaA! ! , As is added in an amount of 0.5 to 1Q mol % based on As, which is a Group V atom at the bottom of the tank. n-type GaAj! The As emitter layer 16 has a thickness of about 300 nm and a donor concentration of about 5 x 10 from the base layer 15 side.
17e11-'', with a first layer (not shown) increasing in Af group composition from about 0.1 to O23, with a thickness of about 900 nm, a donor concentration of about 5 X 10''cm-', and an A1 composition of about 0.
．． A second layer (not shown) with a thickness of approximately 300 μm and a donor concentration of approximately 5×10 I? cm-'', and a third layer (not shown) whose Ai group composition decreases from about 0.3 to O. n° type process Q The thickness of the ivy cap layer 17 is about 1,500λ, The donor concentration is about 15XIQ18cTfl-', and the industrial ivy cap layer 17, the base layer 15, and the collector buffer layer 13 are
An emitter electrode 18, a base electrode 19, and a collector electrode 20 are respectively formed on the substrate to form a heterojunction bipolar transistor.

In this way, by forming the base layer of an npn heterojunction bipolar transistor with a Be-doped p" type epitaxial layer to which Sb is added at the same time, even if a heterojunction n-type emitter region is formed thereon, the Be This prevents the HBT structure from being destroyed due to excessive diffusion into ivy areas and the like.

Preferably, the epitaxial layer is grown using MBE or MOCVD. If these growth methods are used, the stoichiometry of Group I elements and Group V elements is automatically maintained, so when the Sb composition is increased in accordance with the Be concentration in the epitaxial growth process of the base layer, As a result, the composition of other group Ⅰ elements decreases and stoichiometry is maintained.

2. Counterdoping with Sb is effective against Be doping not only in GaAlAs but also in InGaAllAs.
It is also effective for systems.

Non-doped I lattice-matched on semi-insulating 1nP substrate 21 (see Figure 3)
An nAnAs buffer layer 22 with a thickness of about 22,000 layers C1 is epitaxially grown, and on top of this an n0 type (nGaAs collector electrode extraction layer 23 with a thickness of 5,000 layers and a donor concentration of 2 x 10 "cm-") is grown. , and an n-type InGaAs collector layer 24 with a donor concentration of 3 x 10 "cm" are epitaxially grown to form a collector structure. InGaAs lattice-matched to InP is
n o, ssG a o, a, A s, and In
AAAs are I no, szA la, amA
It is S. On top of this collector structure, A1 for Ga
The ratio of the thickness gradually increases from O to 0.2 toward the first ivy layer 26 with a thickness of about i, ooo.
The As base layer 25 is epitaxially grown. Here, in order to lower the resistance of the base layer 25, Be is doped as a p-type impurity at about I x 1020 cm-3, and
The group V element 5b is doped in accordance with the doping amount of ZBe.

On the base layer 25, an In layer is formed, in which the ratio of Al2 to Ga gradually increases from 0.2 to 1 toward the second ivy layer 27.
C; aAI! , the first vine layer 26 of As and InAj
A second vine layer 27 of 2As is epitaxially grown. The thickness of the first industrial ivy layer is about 300, and the thickness of the second industrial ivy layer is about 2,000, and both donor concentrations are about 2 x 10'' cm-3.

Note that the Be concentration as an acceptor in the base layer 25 is 5×
1019 to 5 X IQ "cm", and the Sbl composition is selected from GaAlAs or InGaAj2As so as to correspondingly alleviate the strain in the base layer.
0.5 to 10 m for As, which is a group V atom constituting
Select from the ol% range.

On top of this emitter structure, a first emitter cap layer 28 having a thickness of about 700 nm and a donor concentration of about 2X 10 "cm-' and a thickness of A second emitter cap layer 29 of InGaAs with a donor concentration of about 500 nm and a donor concentration of about IxlO"am-" is grown.

An AuGe eco-vine electrode 30, an AuZn base electrode 31, and an AuGe collector electrode 32 are formed on the second industrial ivy cap layer 29, base layer 25, and collector electrode extraction layer 23, respectively, to form a heterojunction bipolar transistor.

〔Effect of the invention〕

As explained above, in the method for manufacturing a compound semiconductor according to the present invention, by counter-doping Sb to Be doping, a p-type epitaxial layer of GaAlAs or InGaAfAs doped with a high concentration of Be is formed. Even if a layer of other conductivity type is grown, an abnormal increase in the diffusion coefficient of Be can be prevented. Therefore, even if a layer of another conductivity type is grown adjacently, the desired impurity profile will not be destroyed, and the base width can be reduced. It has become possible to easily manufacture a heterojunction bipolar transistor that has a narrow width, low base resistance, and excellent characteristics.

5

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention. FIG. 2 is a configuration diagram of a heterojunction bipolar transistor according to the first embodiment of the present invention. FIG. 3 is a block diagram of a heterojunction bipolar transistor according to a second embodiment of the present invention. ■ ・ ・ 2 ・ 3 ・ 4 ・ 5 ・ 11 ・ 12 ・ 13 ・ 14 ・ 15 ・ 16 ・ 17 ・ 18, ... Be atom, ... Ga (A, j2) atom, ... In atom, ... As atom , ...Sb atom, ...GaAs substrate, ...GaAs buffer layer, ...GaAs collector buffer layer, ...GaAs collector layer, --GaAIAs base layer, ...Ga/! l/! As emitter layer, ...GaAs ξ ivy cap layer, 30...emitter electrode, 6 19.31・20.32・21・・・・22・・・23・・・・24・・・25・・・26・ ・ ・ 27. . . 2B. . . 29.
s collector layer, InGaAj2As base layer, InGaAffiAs th emitter layer, InAfA
s second emitter layer, InAl! As-+InGaAs first vine cap layer, InGaAs second vine cap layer.

Claims (1)

[Scope of Claims] [1] A layer of GaAlAs or InGaAlAs which is lattice-matched to the underlying crystal and doped with Be is formed on the underlying crystal.
In a method for manufacturing a compound semiconductor including a step of growing an epitaxial layer of a type, during the growth step, 5×10^1^
9 to 5 x 10^2^0 atoms/cm^3 Be atoms (1)
and 0.5 to 10 mol of As, which is a group V atom constituting the GaAlAs or InGaAlAs.
% of Sb atoms (5).