JPS58158912A - High mobility semiconductor material - Google Patents

Abstract

PURPOSE:To obtain a mixed crystal semiconductor material of which mobility is high by such an arrangement wherein a buffer layer is deposited on a substrate, and layers of semiconductors, each differs in constitution from other, are alternately and regularly laid over another by the unit of 1mol layer or 2mol layer on the buffer player. CONSTITUTION:On a substrate 7 made of semiconductor or insulation material, a buffer layer 8 of semiconductor or insulation material is caused to grow, and on the layer, a layer 9 of AX single molecule and a layer 10 of AqB1-qX (0<=q<1) single molecule are alternately deposited by 1mol layer up to a desired thickness. Since carriers in the direction parallel with the substrate 7 detect regular lattice potential such as A-X-A-X... in the layer 9, they can realize mobility of high speed without being affected by the influence of alloy dispersion. On the one hand, in the layer 10, alloy dispersion and space charge dispersion exist, except q=0. However, at the time of q=0, the layer 10 becomes BX, and there exists no alloy dispersion nor space charge dispersion. In any case, the average mobility of the layer 9 and layer 10 in the direction parallel with the substrate 7 becomes larger. On the one hand, the mobility of carriers running in the direction perpendicular to the substrate also becomes larger, as the irregularity of potential is lessened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to high mobility layered semiconductor materials having an average composition equal to the desired mixed crystal semiconductor.

One of the conventional semiconductor materials is a mixed crystal semiconductor.

Generally, mixed crystal semiconductor materials have the following advantages.

(1) By appropriately selecting the composition ratio of the mixed crystal, it is possible to match the lattice constant with the substrate for epitaxial growth.

(2) By changing the composition ratio of the mixed crystal, the energy band gap, electron affinity, and refractive index can be changed.

(S) In particular, the lattice constant and energy band gap can be changed independently in a semiconductor mixed crystal.

etc.

However, the carrier mobility of the mixed crystal exhibits a much lower value than the mobility determined by Vegard's law using the mobility of the semiconductor constituting the mixed crystal. This is because carriers in the mixed crystal undergo extra alloy scattering and space charge scattering in addition to the normal scattering mechanism caused by phonons and ionized impurities. Alloy scattering is due to the irregularity in the distribution of the constituent atoms of the mixed crystal, and space charge scattering is caused by the spatial ′d! This is due to scattering due to the load. These effects make it difficult to operate devices such as transistors and photodetectors using mixed crystal semiconductor materials at high speed. This will be explained below using InxGa1-x system S as an example. Figure 7 shows that the ionized impurity density is 77.
Nide-7,39×10"cs-" Ino, 40ao,
Shows the once dependence of the electron mobility of @As (〒', Ka
toda, F. 0saka, and T.

Sugano, Japan, J, pP1. Ph
Vg, vol/, 3. P, 54/-p-56koC/97→). In the figure, real 1d 1.2.8.4 is optical 7-onone scattering, ionized impurity scattering, space charge scattering,
The calculated value of the mobility of alloy scattering is shown, and the broken line 5 shows the calculated value of the mobility obtained by considering the above scattering.
The black dot and the fruit @6 connecting it indicate the mobility obtained in the experiment. In this material, spatial load scattering is a major failure, in the temperature range from 70 to 3 COK! 1L19? It is basic. On the other hand, for example, ND -JNAI NKl0NA -
/X 1011 cm-a mul@uGIL*, ad
In a semi-4 body material like s, alloy scattering becomes a strong scattering element near 100K (A, 0handr
aand L F, Eastman, J, pI)1
．． Phy! 1. vol &/, I), Colo 6 de~p,
21,7ri (/910)). That is, alloy scattering and space charge scattering are one of the main causes that limit the mobility of mixed crystal semiconductor materials.

The present invention eliminates the drawbacks of mixed crystal semiconductor materials as described above and uses a technically easy method to create a semiconductor material that has the same effective composition ratio as this mixed crystal semiconductor material and has higher carrier mobility. It was made with the purpose of providing.

Hereinafter, regarding the present invention, firstly, Mpn, -pX (Qmp
This will be explained by taking a 〈/) type ternary mixed crystal semiconductor as an example.

Here, the constituent semiconductors of this mixed crystal are ■ and BX.

Moreover, M, 1%0 are symbols each representing a metal element, and X and Y%2 are symbols each representing a nonmetallic element.

Figure 1112 is a diagram 1 for explaining the principle of a typical example of the pBl-pX type ternary mixed crystal semiconductor of the present invention, in which a buffer layer 8 is grown on the surface of a clean substrate 7, and on top of that, Molecular layer 9 and AqBt-IX (p≦q〈/)-monolayer 10
tt1 This is a fabric in which molecular layers are alternately laminated to a desired thickness.

Here, it is also possible to set the stacking order to be MqIBl-(X-AX. However, the relational composition between p and qg is the same as that of the mixed crystal. It is easily possible to create materials laminated in monolayer units in this manner using the current epitaxial growth technique 1#. The carrier parallel to the substrate is 1. ■In the monomolecular layer 9, MuX-Mu-X10. Because of the sense of a regular lattice potential, high-speed mobility can be achieved without being affected by alloy scattering and space charge scattering. On the other hand, in the monomolecular layer 10 of QBI-qX (θ≦p/), alloy scattering and space charge scattering exist as in normal mixed crystals except for q-O. However, at q-θ, the monomolecular layer 10 of Mu, Bl-, and X becomes BX, and there is no alloy scattering or space charge scattering. In any case, the average mobility of the α single molecule single layer 9 and Mu, B, 1X monolayer *20 in the direction parallel to the substrate is greater than the mobility of the pBl-pXljj mixed crystal semiconductor. On the other hand, carriers traveling in the direction perpendicular to the substrate are
The potential is -A-X-,..., A-X-mu-X-X -A-X +,.... Since the irregularity of the potential is reduced, alloy scattering and space charge scattering are reduced. Therefore, the carrier mobility in the direction perpendicular to the substrate is
i-pX M l! The mobility is greater than that of i-crystalline semiconductors.

The above is an explanation of the mixed crystal semiconductor of the type pBi-pX ((15≦X〈/), but the explanation is for the mixed crystal semiconductor of the type pBi-pX ((1
3≦X〈/)-MuqB1- q X AqB 1-
A similar effect can be obtained by stacking two molecular layers regularly, such as q
, Bl-, X-, . . , a similar effect can be obtained by stacking bimolecular layers and monomolecular layers in an orderly mixture. In short, ordered stacking reduces alloy scattering and space charge scattering and provides a significant increase in carrier mobility.

Next, ApBqOi-p-qX (+≦p</, +≦q
〈/.

A quaternary mixed crystal semiconductor of 1≦p+q</) type will be explained. Here, the constituent semiconductors of the mixed crystal are Mx, nx and Cx
It is.

FIG. 3 is a diagram for explaining the principle of a typical example of the P"tlol-P-11X type quaternary mixed crystal semiconductor of the present invention. A breadlayer 8 is grown on the surface of a clean substrate 7, and On top of that, ■ monomolecular layer 11 s ilX monomolecular layer 12AyB
101-r-gX (0≦r</, 0≦s</, 0≦r
+s</) monomolecular layers 1B are alternately laminated in seven molecular layers to a desired thickness. However, 1 of plq, r, and s
The +Ii coefficient is p-4-<i+r> (1-+(/+a)), and the average composition of this semiconductor material is equal to that of the mixed crystal. In this case as well, the ApB l + px type ternary described above The same argument as for mixed crystal semiconductors can be developed, and the layer 11, the BX layer 12, and the layer Bao1-rs layer 18 are made one molecular layer each.
“The carrier mobility of the semiconductor material stacked in multiple layers alternately is greater than the mobility of the mixed crystal.It goes without saying that in the ApBqOl-p-qX type quaternary mixed crystal semiconductor, i
The above conclusion does not change for mixed crystals having p and q values other than Hatake. In this example, there are many methods for laminating one molecular layer at a time. Whatever the layering method ``11'', a regular layering method with at most two molecular layer units or less, pBi-pXqY
i −q (0,3≦p</, Q, li'−!q</
) The M quaternary mixed crystal semiconductor will be explained. Here, the constituent semiconductors of the mixed crystal are of the following types: AX, BX, AY, and BY.

FIG. q is a diagram illustrating the principle of a typical example in which the present invention is applied to an ApB l-pXqYt -q type quaternary mixed crystal semiconductor. A buffer layer 8 is grown on the surface of a clean substrate 7 1
．． Kin monomolecular layer 14, BX monomolecular layer 15, AY monomolecular layer 1
6. ArBt-rx# Yl-a monolayer (θ≦r〈/
, O≦tx</) 1 te is alternately laminated one molecular layer at a time to a desired thickness. However, pSq and rsB
The relationship is p-+(co+r) q-4-(2+t), and the average composition of this semiconductor material is equal to that of the mixed crystal. In this case as well, the above pB1. -p X 1jJI
#Al11+ similar to a ternary mixed crystal semiconductor is established, and the carrier mobility of this type of semiconductor material is the mobility type of the mixed crystal,
A similar conclusion can be obtained for the ApBI-pXI-qYq type four-type warm mixed crystal semiconductor. In this example, there are many methods for regularly stacking layers while maintaining no single molecule layer. Regardless of the stacking method, a similar mobility increase effect can be obtained by regular stacking of at most two molecular layers or less1.
The above examples were aimed at suppressing alloy scattering and spatial brazing scattering and increasing the mobility.

Next, an example of the high-mobility semiconductor material that can further suppress ionized impurity scattering and achieve even higher mobility will be described.

FIG. 9 suppresses alloy scattering and space charge scattering, and deposits a stacked portion 85 with a low-strength semiconductor. It has a band gap that is roughly larger than the effective band gap of this laminated portion 85, and is deposited in the above-mentioned void. Further, 8 layers of semiconductor material doped with the same semiconductor material as Pi or n-type are deposited.

Due to this twist *i, the electrons or holes in the p-type or nm-doped semiconductor material 81 are transferred into the laminated part 85 of the pine 27', which is one nuclide layer. Mesido Y Itza 7mm storage layer part 85 in 8b
The p-type impurity concentration is low, and the concentration can be controlled by the impurity concentration of the p-type or n-doped semiconductor material 87 and the thickness of the layer 8G with the low impurity concentration. Fast mobility is achieved because it is not subject to impurity scattering as well as scattering and space charge scattering.

Next, the structure of the buffer layer will be explained.

The buffer layer is necessary to eliminate the shadow of the substrate on the laminated portion and to form the layered portion with good characteristics. When the lattice constant of the substrate and the effective lattice constant of the laminated portion match within a range of 0.3%, the 7th buff layer is made of the same material as the substrate (2) The same material as the laminated portion・However, the film thickness is a!fμRo ~ IO Koejima (8) Semiconductor material whose lamination constant matches the substrate or the laminated part within 0.3%, or (1) to (a) of the laminated part or more You can choose one of them.

When the lattice constant of the substrate differs from the effective lattice constant of the laminated portion by more than the above value, the buffer layer should have a lattice constant equal to that of the portion in contact with the substrate, and For the part in contact with the semiconductor material, it is appropriate to use a semiconductor material whose lattice constant is changed as shown in (g) or φ) or (C) in Figure 11 so that the effective lattice constant is almost equal to the effective lattice constant of the semiconductor material. And Ji//#j! J(g) is the change in lattice constant m
Figure 11 (0) is the one in which the lattice constant is changed stepwise, and Figure 1/(C)
The lattice constant is changed in a sawtooth pattern.

The semiconductor material constituting the buffer layer may be an ordinary semiconductor material, a compound semiconductor material, or the laminated portion of the present invention, as long as it satisfies the above requirements.

1. Next, embodiments of the present invention will be described.

FIG. Then, an InP buffer layer 19 is grown. Furthermore, InAl2G and GaAs21
When these are alternately laminated one molecular layer at a time, the average 1 of this laminated portion becomes Ino, 6Ga4-muS. Mixed crystal In@, 5
Since the lattice constant mismatch between eGaO, ism S and InP is very small at 0.2%, InAs/GaAs layer 2
The crystallinity of the InAs/GaAs layers 20 and 21 is extremely good because the disturbance in the crystallinity at the interface between the InAs/GaAs layers 20 and 21 can be ignored. Alloy scattering and space of InAs/GaAs layer 1! ! Since the influence of #scattering is extremely small, it is expected that a value of approximately /×IO'Cd1- can be obtained as electron mobility at room temperature.

In the example shown in FIG.
θ) is possible. Figure 5 shows that the average composition is I
This is an example in which semiconductor materials such as ns, sGa@, and -muS are grown on the InP substrate 18. In particular, as an example in which the lattice constants are almost matched, the combination of the substrate and the laminated portion as shown in Table 1 is Therefore, it is expected that the present invention will significantly increase the mobility of these semiconductor materials. Even if lattice matching cannot be achieved between a mixed crystal having the same composition as that of the laminated portion and the substrate, a significant increase in mobility can be expected by laminating the layers in accordance with the example described above.

Margin table 1 ``Ino, 52AIo, 48ASInP,'■nAS-
■no, o4A1o, 96ASi Ino, 5Gao,
5P GaAs InP-GaP:, I
no, sA 1 o, sP, GaA
sInP-AIP: Alo, 5Gao,
5As GaAs l AlAs -GaAs1A
IXGa1-xSb' GaSb
' Garb-, A12xGa1-2xSh
(x<0.5)24, InAs! 5, Ale, 5s
sGILs, tmsIno, ssAg 26 alternately 1
When laminating molecular layers one by one, the average composition of this laminated part is Ale.
, pe +Ga@, s q *Ins, h 0 mixed crystal Ale equal to sAI, a @4Gas, s v aIns
, Since there is almost no mismatch in the lattice constants between h sm 8 and the InP substrate 22, GaA8/-) jnAs/Ale, a s zGas, 1111
Ino, s sA8 Laminated part 24.25.26p In
There is no disturbance of crystallinity at the interface with P22.

■ -GaAs/InAs/Ale, 5ssGa@, t
msIno, the influence of alloy scattering and space charge scattering of the s+sAs layer 24,25,26 is mu1. ■Fable G5L@, 11
Since only electrons traveling through the 8InQIlum 8N 26 are received, the average electron mobility is expected to show a large increase, especially at low temperatures.

In the above example, the buffer layer 28 is In., 5sAl.
e, I used 48A8, but In・, s*Al・, 48muS
It is clear that a similar increase in mobility can be obtained by using In., BGa., 49AB, or InP instead of . Typical composition 1e-ss*GILe, ats Ins, s
InP noodle plate 2 with just the right lattice constant for SM8
Although we have described an example in which the lattice constant is matched to that of the substrate, we have described an example in which the lattice constant is matched to that of the substrate.
Regarding the mixed crystal seed semiconductor of No. 1, there are combinations as shown in Table 2, and it is expected that the present invention will significantly increase the mobility of these semiconductor materials. In Table 2, for ease of use, the lamination is made with one molecular layer at a time, but the rule is up to two molecular layers.
li [51 & 4” II body f) As an example, the average composition is Ga・, IIn・, 1Ail・, s8b・, I
FIG. 3 is a diagram illustrating an example in which a semiconductor material of is created on a Ga8b substrate 37. GaO on the Ga8b substrate 27,
The IIn., ins, i8b*, s buffer layer 28 is grown. Furthermore, GaAs Z & InA186
, In8b 81 , and Ga8b8m are alternately laminated one molecular layer at a time, the average composition of this laminated portion is Ga., I
In・, IA8・, ssb・, I.

The lattice constants of the mixed crystal Ga@, 1IflsjA11*,s8be,i and the Ga8b substrate 2F are almost matched. Therefore, there is no disturbance of crystallinity at the interface between the first layer portions 29.8G and 81.8fi and the substrate. GaAg/In
As/In8b/Ga8b layer 29°8G, 81.82
Since the carriers are not affected by alloy scattering and space charge scattering, high-speed electron mobility is achieved.

In the example of the pB1-pxCLyl-11 mixed crystal semiconductor shown in the t4g diagram, Ga.4In.
, im8., 18b., and S were used, but similar effects can be obtained by using Ga5b. Other modules PB1-Pxlly
Even in l-Q m mixed crystal conductors, if the laminated structure is selected appropriately, carriers can be transferred and laminated one molecular layer at a time, but regular lamination of up to two molecular layers can also produce a semiconductor with high-speed mobility. It is clear that the material is available.

Next, an example of a semiconductor material that suppresses not only alloy scattering and space charge scattering but also ionized impurity scattering and enables high-speed mobility will be described. FIG. 1θ is a diagram for explaining the configuration of this example.
A buffer layer 89 of 41 Ine, i- is deposited, and a single-molecular layer of GaAs 40 and a single-molecular layer of InAs 41 are alternately laminated as a laminated portion. However, neither G&A8 nor InAB is doped with impurities.

Mu1 negative, sIn fist, sA8 without further doping impurities
The phase shifts to around 4B, and a two-dimensional electron conductive layer is formed.

High mobility can be achieved because electrons in this channel are hardly affected by alloy scattering, space charge scattering, and ionized impurity scattering. Of course, M1・, BIn・, 5 people 842.4
Instead of 8, MlAs! One molecular layer of I and one layer of InAg
High electron mobility can be achieved even by depositing one molecular layer at a time.

The effects obtained by the semiconductor material of the present invention are as follows: A semiconductor material whose average composition is the same as that of a mixed crystal semiconductor, and a constituent semiconductor of the mixed crystal are regularly arranged in one or two molecular layers. When configured by stacking layers, alloy scattering and space charge scattering, which are characteristic of mixed crystals, are not effective in this semiconductor material, so carrier mobility in this semiconductor material can be greatly increased.

It can be applied to electronic devices and integrated circuits using the same, obtoelectrolux devices and integrated circuits using the same, and greatly contributes to improving their performance.

4I% Brief explanation of drawings 1st v! A diagram explaining the temperature dependence of electron mobility of J Lt In・, @Qa・, and As (T, Katoda,
7.08JKL and T.

A schematic diagram of a typical example of a Yl-qM quaternary mixed crystal semiconductor,
No. S-#A has an average composition of In・, BGa@
, hmS is a schematic diagram of the construction of an embodiment applied to a semiconductor material, and FIG. A schematic diagram of the structure of an example applied to a semiconductor material that is a buffer layer for % M8, and an example of a semiconductor material that suppresses ionized impurity scattering and achieves high-speed carrier layer mobility in the InAa/GaAs layer portion. This is a schematic diagram of the configuration.

In the figure, 1 is the electron mobility due to optical 7-onone scattering, 2 is the electron mobility due to ionized impurity scattering, 8 is the electron mobility due to space charge scattering, 4 is the electron mobility due to alloy scattering, and 5
is the calculated value of mobility obtained considering scattering of 1 to 4 (black dots and solid line 6 are experimental values), 7 is for epitaxial growth &&
, 8 is a buffer layer, 9 is a single molecule layer of ■, 10 is a mu, B
One molecular layer of t-tX, 11 is one molecular layer of ■, 13 is BX
18 is one molecular layer of Murnsci-r-aX, 14 is a child layer, 21 is one molecular layer of G&A8, 22 is In
P substrate, layer 80 is InAg 1 molecule layer, 81 is In8
b 1-molecular layer 182 is a Ga8b 1-molecular layer, 88 is a substrate, 84 is a buffer layer, 85 is a laminated portion, and 86 is an impurity In/0% S layer with a wider band gap than the laminated portion and the same lattice constant. .

Figure 71 Figure 2 Spear 3 7f5 diagram Figure 76 Figure 78 age 9 age 10 Figure 11 Lazy house Mount Eizan

Claims (6)

[Claims] (1) A semiconductor or insulator serving as a buffer is deposited on a semiconductor or insulator substrate, and semiconductors having different compositions are deposited on the semiconductor or insulator in units of one molecular layer or three molecular layers! A high mobility semiconductor material characterized by having a laminated portion in which a finite number of 7Ji layers are deposited. (2) A high-mobility semiconductor material according to claim 1, wherein the laminated portion is made of one type of semiconductor. (3) A high-mobility semiconductor material according to claim (1), characterized in that the laminated portion is made of a three-layer semiconductor. (4) A high-mobility semiconductor material according to claim (1), wherein the laminated portion is made of several types of semiconductors. (5) In the high mobility semiconductor material according to claim (1), as a buffer, at least one type of semiconductor having compositional membership with each other is regularly arranged in a finite number in units of one molecular layer or in units of two molecular layers. A high mobility semiconductor material characterized by being constructed by laminating layers. (6) Claim No. (In the semiconductor material according to claim 0, a laminated portion made of a semiconductor with a low impurity concentration has a band gap wider than that of the laminated portion, and an effective lattice of the laminated portion. depositing a semiconductor material with a low impurity concentration having a lattice constant equal to
A high-mobility semiconductor material further comprising a p- or n-doped semiconductor material deposited on the semiconductor material with a low impurity concentration.