JPS5940800B2 - Double-layer epitaxial growth equipment for compound semiconductor mixed crystals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for two-layer epitaxial growth of a compound semiconductor mixed crystal under the vapor pressure of at least two or more high vapor pressure elements.

Conventional crystal growth for compound semiconductors involves differences in the vapor pressure of each constituent element in both melt growth and solution growth, but a growth method that does not take into account the difference in vapor pressure has been adopted.

For the past few years, B2O3 and Ba have been added to the melt during GaP melt growth to prevent high vapor pressure elements from flying out.
A method to prevent evaporation of phosphorus by placing a liquid seal with low specific gravity such as Cl2 (Yo Ap p 1. Ph y s, 33201
61962) etc. have been used to prevent the evaporation of elements with high vapor pressure, but such methods cannot completely compensate for evaporation and some of the elements scatter through the coating film.

Additionally, there is a great risk that these film materials will dissolve into the crystal.

Even in melt growth, which requires high temperatures, vapor pressure is not controlled, and in solution growth, where growth is performed below the melting point of the crystal, the molar content of crystals in the solvent is small, so the vapor pressure is not controlled. It is a well-established theory that the vapor pressure of elements with high vapor pressure decreases, and that the stoichiometric composition of the crystal naturally becomes the correct composition during growth, so no consideration was given to elements with high vapor pressure. good.

But this was a complete mistake.

However, due to advances in crystal growth technology and social demands,
It is necessary to use high-quality, high-purity crystals to create long-life, highly reliable semiconductor devices.

The most problematic defect in compound semiconductor crystals is stoichiometric composition (stoichiometry).
It is expected that this is caused by a deviation from a crystal in which As and As exist in the same proportion.

In other words, it is thought that the biggest and final barrier to producing crystals of the highest quality lies in how the deviation from the stoichiometric composition can be controlled.

As the current state of compound semiconductors is as described above, vapor pressure control has not been performed at all for ternary or higher mixed crystals, which are expected to be in great demand in the future, and the present invention will improve the characteristics of all current mixed crystal devices. can be dramatically improved.

As a mixed crystal ■ (■,■)・■(InGa)p, (In.

Ga)As, (In, Ga)Sb, (
Ga.

AI)P, (Ga, AI)As, (Ga, AI
) Sb.

(In, Ga)N, (Ga, AI)N, (In.

AI)P, (In, AI)Sb, (In, AI
)As.

(I n , A I ) N, etc. In this case, the group ■ element pr A sy N + S t
) vapor pressure control is required.

■ Ga(As, P), In(As,
P), AI(As, P), In(AsSb), In(P
, Sb), Ga (As, 5b) Ga (P, Sb), A
I (As, Sb), AI (P.

(■
...m)(v...■) Group compounds exist, and in this case, it is necessary to control the vapor pressure of two or more Group (■) elements having high vapor pressures.

■ (Zn, Cd)S of (II, II) and VI, (
Zn.

Hg)S, (Hg,Cd)S, (Zn,Cd)Se.

(Zn, Hg) Se, (Hg, Cd) Se, (Zn.

Cd)Te, (Zn, Hg)Te, (Cd.

Hg) Te, etc. and ■' II (VI, VT) Zn (S, Se), Cd (
S.

Se), Hg (S, Se), Zn (S, Te).

Cd (Se, Te), 'Hg (S, Te), Zn (Se
, Te), Cd (S, Te), Hg (Se.

Te) etc. ■■' etc. (■...II) (VI...
■) Since the vapor pressure of each element is high,
It is better to control vapor pressure for three or more elements.

Furthermore, Cd I n2S4 of (II-1[-VI)
.

For CdInSe, etc., it is necessary to control the ■ and ■ group elements.

Also, CdGeAs2 + cci GeP2 t Cd
In II-IV-V mixed crystals such as 5nP2 pZnSnP2, it is necessary to control the vapor pressures of group V elements.

Furthermore, the mixed crystal system increases and the four elements (Al tGa)AsP
, (In+Ga)AsP, (In, AI)AsP,
(In,.

Ga)SbAs, (AI, Ga)PSb, AI(
In all cases, the vapor pressure of group (1), group V, and group (2) elements is usually high, so crystal growth under the vapor pressure of these elements is required.

Furthermore, (Pb, 5n)Te, (Ge, 5i)Te.

(IV・Ge (Te, S), 5j (Se, Te), etc.
IV) (VI-VJ) Mixed crystal, CuAlS2°C
uGaS2. CuAlSe2. AgIn52. AgAl
IIl such as Te2 [VI mixed crystal, Cu5PS41 Ag
IVVI mixed crystals such as As S2'tAg3As83, H
g3S2C12tZn3Se2C12r Cd3Te2
IIIVI mixed crystal such as C12, GaGeTe2. In5
nTe2rInSjTe2. l[]VVI mixed crystals, such as
Furthermore, as mixed crystals of four elements, GeAs-Ge5,
IV such as GeP-Genet SnP-8nTe
VIVVI mixed crystal, CuCl-GaP.

II such as CuC1-GaAs tcuBr-InAs
■Mixed crystal, (Cd Ge P2)-GaP, (Hg
S i As2 )-GaAs, (ZnGeP2)-
■IIVV mixed crystal such as InAs, Ge Te e-Ga
A s , S i 5-GaP.

Il [IVVVI mixed crystal, C such as 5nSe-Garb
uAlS2 ZnS, CuGaS2 Zn5e
.

III [such as AgA I S C2-Cd T e
VI system mixed crystal, ZnTe-PbTe, Cd5e-PbS
, I-IV-V-VI mixed crystal systems such as HgTe5iTe, etc., it is preferable to grow the crystal under the vapor pressure of one or more elements.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram of a conventional liquid phase epitaxial growth apparatus 1, in which a source 3 of the crystal to be grown is placed in a solvent 2 of Ga, In, etc. and the growth temperature is lowered to grow onto a substrate crystal 4. It is.

In this case, high vapor pressure elements such as As and P during growth
evaporates from inside the boat.

FIG. 2 shows a part of the growth apparatus of the present invention, which is equipped with two steam pressure pipes.

Two pressure-controlled furnaces 17, which are separate from the growth furnace 16, are provided, and are designated 17' and 17'' from the low temperature side, respectively.

A solvent 19 is placed in the melt tank 18, a source crystal 20 is floated on top of the solvent, the temperature of the source crystal 20 is made slightly higher than the temperature of the substrate crystal 21, and the source crystal 20 is dissolved and diffused onto the substrate crystal. It grows crystals.

If the mixed crystal to be grown contains two high vapor pressure components, it is preferable to control the two vapor pressures independently, and if the mixed crystal is conventionally configured integrally with the growth furnace, it is preferable to control the two vapor pressures independently. In order to overcome this drawback, a vapor pressure controlled furnace was constructed separately, and each component element was placed in a chamber in which each component element was placed independently in the furnaces 17' and 17'' whose temperature could be controlled independently. This is a single layer epitaxial growth apparatus having a structure in which the open end of a pressure supply pipe made of thin quartz having diameters 22' and 22'' is inserted into the upper part of a melt tank.

The upper space of the melt tank does not have to be completely airtight, but
It needs to be airtight enough to maintain pressure.

FIG. 3 shows an actual example of a two-layer epitaxial growth apparatus using a growth apparatus having this basic structure.

FIG. 3 shows, as an example of the present invention, a growth apparatus in which GaAsP is used as a mixed crystal in which the vapor pressures of two elements need to be controlled.

In GaASl-xPx, G is lower than GaAs depending on the value of X.
Mixed crystals having the properties of each crystal up to aP can be grown.

Port 6 has A for double layer epitaxial growth. 20g of Ga7゜7' as a solvent and 2g of GaAsP polycrystal corresponding to the composition of GaAs1-xPx to be grown as a source crystal or GaAs
, a considerable amount of GaP is introduced into the source crystal part 8,
A temperature difference 10 of 20° C. is provided between 8' and the substrate 9.

Conventionally, the temperature difference was created by wrapping a heater around the tart tank in the growth furnace and passing an electric current through the heater, but this method was prone to contamination due to the material of the heater, and a higher purity In order to overcome this drawback, a heater was not placed inside the quartz tube, and an electric current was passed through an extra heater 31 formed above the growth furnace 13. .

Furthermore, as shown in the figure, thin quartz tubes 10' and 10 (inner diameter 3 mmφ), which have a place for introducing component elements of the mixed crystal in the low temperature part, are placed over the melt tank with a lid 11 so as to be semi-closed.
Insert ', 11''.

Metal arsenic (As) 1 is placed at the component element injection point in the low temperature section.
By putting 1 g of phosphorus (P) 1 and 0.5 g of red phosphorus (P) 12 and changing the temperature of the control furnaces 14 for As and 15 for P, which are separate from the growth furnace 13, the As pressure and P pressure in the growth part can be made independent. can be controlled.

When controlling the vapor pressure of the same element to be the same, a structure in which pipes are inserted in series between A and B as shown in the figure may be used, but it is obvious that a vapor pressure supply source may be provided for each melt tank. Will.

The growth temperature was 800°C, and Ga A sO, 7po
, 3 crystals at an As pressure of 10°50 t 100 + 5
00 T o r r y P pressure 10.50°100
．． 500 Torr and 4 types each (As pressure, P pressure):
(10,10), (10,50) (10°100)...
Two-layer epitaxial growth was performed using 16 combinations such as...

In the two-layer growth, as shown in FIG. 3, after the growth on the melt layer B is completed, the substrate 9 is deposited on the carbon slider 9 from Ga7'.
' by moving it to the left, moving the substrate directly below the melt tank A, and growing in the melt layer A in the same way, a P-N junction can be formed on the substrate crystal 9. .

The slider can be moved manually or automatically from outside the furnace.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a conventional liquid phase epitaxial growth apparatus, FIG. 2 is a schematic sectional view showing the basic structure of the epitaxial growth apparatus of the present invention, and FIG. 3 is a schematic sectional view of an epitaxial growth apparatus according to an example of the present invention. It is a diagram.

Claims (1)

[Claims] 1. In the crystal growth of compound semiconductor mixed crystals by the vapor pressure controlled temperature difference method, the structure of the crystal growth furnace is such that an extra heater is placed at least above the main heater in order to form a temperature difference in the solution, and Each solution tank is equipped with at least two vapor pressure supply pipes communicating with a vapor pressure source for controlling the vapor pressure of the vapor pressure component, and the vapor pressure control furnace for controlling the vapor pressure is configured separately. A compound semiconductor multilayer epitaxial growth device characterized by: