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Thermodynamic analysis of GaAs growth by cold-wall metalorganic-chloride vapor phase epitaxy
CRYSTAL GROWTH
Journal of Crystal Growth 1 1~(1991)211 215 North-Holland
Thermodynamic analysis of GaAs growth by cold-wall metalorganic-chloride vapor phase epitaxy Hitoshi Ikeda, Kenichi Saitoh, Yoshitugu Hasegawa, Akinori Koukitu and Hisashi Seki Department of Applied C/iconstrv. J~acnltvof Technology, Tokyo finn erlity of Agrcnltiue and ]echinologs, Koi~anei, IOk)o I~4,Japan
A thermodynamic analysis of cold wall MO chloride VPE growth of GaAs using triethylgallium and AsCI is described. The behavior of the equilibrium Partial pressures shows features ol both the chloride VP[ and the MOVPE systems. Fhe calculated growth rate is compared with the experimental data reported previously. The experimental growth rate as a function 01 the input partial pressure 01 TEG. the reciprocal of substrate temperatures and the input III V ratio are well explained by the thermodynamic model
1. Introduction Recently, we have reported the growth of GaAs using triethylgallium (TEG) and AsCI in a coldwall reactor [1].We call this method the cold-wall MO-chloride VPE. In the method, AsCl~is used as the arsenic source, instead of fatally toxic AsH which is used currently as the arsenic source in metalorganic vapor phase epitaxy (MOVPE). The reactor for the cold-wall MO-chloride VPE is almost the same as that for conventional MOVPE. Consequently, we can expect the same advantages as those of MOVPE. For example, it will have similar suitability for large-scale production and versatility as MOVPE, but without the use of hazardous source materials. In addition, it will be possible to grow aluminum-containing materials which are difficult to grow in chloride VPE. In previous papers [2,3], we have shown that thermodynamics provides useful information for the understanding of vapor phase epitaxy. While these studies clarified the thermodynamic characteristics of MOVPE, molecular beam epitaxy (MBE) and atomic layer epitaxy (ALE), those of the cold-wall MO-chloride VPE have not been studied yet. The purpose of this paper is to de-
with the experimental data. In order to calculate the equilibrium partial pressure, a previously developed computation method [41 has been applied to the growth system of the cold-wall MO-chloride VPE. It will be shown that the main features of the growth rate are explained by using the equilibrium model.
2. Calculation procedure The growth rate study on the cold-wall MOchloride VPE has shown that mass transport is the rate-determining step in the overall process [1]. This fact indicates that the rate of reaction is controlled simply by the rate of arrival of the growing species at the vapor solid interface. Under these conditions, we can assume that chemical equilibrium is established at the vapor solid interface, because the rate of chemical reaction is considered sufficiently high compared to the arrtval rate of reactants. The input TEG i’. decnmpnsed irreversihly according to the following homogeneous reaction near the vapor solid interface [5]: Ga(C,H.~)3(g)—s Ga(g) + 3 C7H4(g)
scribe a thermodynamic analysis of the cold-wall MO-chloride VPE and to compare the results 0022 0248 91 $03.50
1991
Elsevier Science Publishers By. All rights reserved
+
~H,(g). (1)
H. Ikeda et al
212
Thermodynamic anal~its of GaAs grovoh hi cold is all MO C hi/omide VPI
Since the input TEG is decomposed completely and the reverse reaction does not proceed, the ethylene (C,H4) in the products is considered as the inert gas in the present analysis. The following 9 Species arc chosen as the necessary vapor species in analysing the vapor growth of GaAs: GaCI, GaCl5, Ga, As4, As~, AsCl~,HCI, H~and C)H4. Other species which might possibly exist in the reaction system, Cl2, C2H4CI,. etc. were neglected. The chemical reactions which connect all the species at the vapor solid interface are: 2 GaCI(g) + ~As4(g) + H7(g) 2 GaAs(s) + 2 HCI(g),
(2)
2 Ga(g) + 2 HCI(g) GaCI(g) + 2 HCI(g)
(3) (4)
where ~ is the input partial pressure of TEG. Eq. (12) expresses the total pressure of the sys tem. Eq. (14) expresses that the deposition oceurs in the ratio of I to I for group Ill and group V elements. The equilibrium partial pressures at the va por solid interface can be obtained from the solution of the above simultaneous equations. The calculations were carried out by using a method similar to that developed previously [4]. The values of the equilibrium constants were the same as those in our previous papers [4.61,except that of eq. (II) [7].
3. Results and discussion
As 4kb/ ( \
‘~
2 GaCI(g) + H,(g), GaCI5(g) + l-I,(g),
As 2kb’’ ( ~\
(S\‘ ‘
AsCl~(g)+ ~H~(g)
.~As4(g)+ 3 HCI(g).
(6)
The equilibrium partial pressures of gaseous species over GaAs are shown in figs. I and 2. In the first figure, the tnput partial pressure of ‘lEG (P~)is set to the same partial pressure as that of the thermodynamic analysis of MOVPE process .
.
The equilibrium equations for these reactions are as follows: K1
P~(I/P(~(IP~,’Pit,.
(7)
K
P~,(P~/P(~~
(8)
K~ PG( I ~P1 /P(;( I P~
(9)
P11~5x10
100
.
III V
=
3
-
C2H4
-
K4
~atm H2
(10) (11)
P.~,/~A~,’ 1’A~4’ti( /P~ ~Pt~2
-
10
K, From the conservation constraint we have
-
As 2
i
+
Pfl
+
J(,~ç~ + Py,
+
P~~
1,
+
+
[(P~~,
i
+
~
(4PA, +
+
~
X (P11~~ + 2 Pit
~lEG
p(
~tt4’
~A,cI
+
~t t( I
+P11(~j
-
10
10
-
(13)
P~,,)
+
)
+
(12)
P(,,(i+3P~(i+3P\,(I
B
‘A~
PA~(i)j
15
500 ~.
GaCI3
-
(14) i~ -
-
I
600 100 Temperature °C
Fig I. The equilibriumtensperatule. partial pressures as
800 a function
of
H. Ikeda ci al.
/
Thermodynamic analy.os of GaAs growth by cold-wall MO chloride VPE
[2,3,8] for comparison. An interesting feature in
T = 650°C
these figures is that the partial pressures of GaCI, HCI, C2H4 and Ga are involved in the same figure. The former two species are the major vapor species in the chloride VPE system and the
10
U
213
P0° = 5x 10”~atm
_______________________________
H2
-
-
GaC
MOVPE system. Consequently, the cold-wall
latter twoinspecies dentally, MO-chloride the VPE present are system observed system, showscommonly C7H4 both features is anininert the of the chloride VPE and the MOVPE systems. Incigas and the partial pressure of Ga is low. If we neglect these species, the general features of the equilibrium partial pressures become quite similar to those of the chloride VPE system [ô]. Therefore, the cold-wall MO-chloride VPE system is regarded as the chloride VPE system rather than the MOVPE system. In the equilibrium model described above, the growth of the epitaxial layer is controlled by diffusion of the group III elements through the boundary layer [9]. According to Shaw [101, the growth rate under the mass transport type II or
~52HcI
E
I
-
10
10
-
_GaCL1 -
Ga -
- ____________ -
-
_)~~o 10
~
it
—~~i
02
06
I
1
2
~/v
4 Ratit
iii ii
6
10
20
Fig. 3. The equilibrium partial pressures as a function of the
T = 650~C 10
~
V
=
3
input 111 V ratio.
_________________________________
0
H2
-
10
diffusion limit at constant pressure is expressed as follows:
GaCI
rwhere kg is the mass transfer coefficient, P~1 (16) is the kg(P~~ttP111), input partial pressure of the group III element, and P~~1 is the equilibrium partial pressure at the substrate surface. In the cold-wall MOchloride VPE system for the GaAs growth,
~::~~AS~
1 O~10
r
kg[P~uo
~kg(P~EG
(FG,c+P(,( Pc’(I).
+P~,)]
(17)
Ga
AsCI3 10 10
10 P11~ (atm)
10
Fig. 2. The equilibrium partial pressures as a function of the input partial pressure of friethylgallium.
The last equation is obtained from P~act>> + P6~).Then we find again that the coldwall MO-chloride VPE system is regarded as the chloride VPE system, though it includes C2H4 and Ga species. Ftg. 3 shows the equtltbrium partial pressures over GaAs as a function of the 111/V ratio. At Ill/V 4, a drastic change of the partial pressures is seen. This is a remarkable feature gener-
214
H. Ikeda ci al.
Thermodynamic analprs of GaAs growth hi cold wall MO-chloride UPI
ally obtained in the cold-wall MO-chloride VPE system using AsCl~ as a chloride source. The broken line in the figure shows the vapor pressure of the liquid gallium. Therefore, we would have the deposition of a gallium droplet if the Ill/V ratio is larger than 4. Fig. 4 shows a comparison between the calculated growth rate and the experimental data. The experimental data are from our previous paper [I]. In the calculation of the growth rate, the value of k I’ was determined to be 2.77 X i0~ atm by adjusting to the experimental data of P~ 1.13 x 10 atm. It is seen that the agreement between the calculated and experimental growth rate is quite good. In fig. 5, a similar comparison is shown for the temperature dependence of the growth rate. Good agreement is obtained between the calculated and experimental growth rates, in the temperature range where the growth rate is nearly independent of deposition temperature. Therefore, we can conclude that mass transport is the rate-determining step in this temperature range. On the other hand, the experimental growth rate deviates from the calculated values at high tem-
/ I
•
0
/ ExperImental
—
/ /~
•
-
E
/
-
-
/ /0
0
5
.
—
Experimental Calculated
5
4
o
PnEG 15x10 atni tatm PA 1CI1 3,7500 mit TttalFlow:550m1
1 1.0
11 1000
Fig.
~.
12 T (K)
13
Comparison between the experimental and calculated
growth rates as a function of the reciprocal of temperature.
peratures. The surface morphology of the grown layers became hazy under these conditions. This may he attributable to the premature deposition of theofmetalorganic compound or the wall deposition GaAs. Finally, a comparison for the effect of the
Tni :650 C ~/V:4 Total Flow: 550m1 mm
/
‘ .
.
/ 0
// 0
/
/
0
.
larger than 4. Although some difference is oh served between the experimental and calculated growth rates, the general features of the experimental data are well explained by the calculation. The observed difference between the experimen tal and calculated growth rates is probably due to the fact that TEG is not sufficiently saturated in H gas in the experiment.
E
/
0
—
0/
.
-
I
o ~~
~ ~ 10
‘
500
I
I
tnput parttal pressure ratto between TEG and AsC1 5 on the growth rate is shown in fig. 6. The broken line in the calculated curve indicates that the deposition of a gallium droplet would he observed in the range because the Ill/V ratio is
Calculated
/ -~
I
/
• 10
100
Temperature ( C) 650 600 550
10
4atni
)
15
20
Pncu the ) xlO Fig. 4. Comparison between experimental and calculated growth iates as a function of the input partial pressure of triethylgallium
4. Conclusions A thermodynamic analysts of the cold-wall MO-chloride VPE growth of GaAs using triethyl-
H. Ikeda et al.
8
/ Thermodynamic analysis of GaAs growth by cold-wall MO-chloride VPE
I
0 0 —
-~
•
0
Acknowledgement
0 .
PxscI3 :2.51x10 4atm Tsuh :650 C Total Flow : 550 ml nile
0 0
served good agreement between the experimental and calculated growth rate shows that the reaction of the cold-wall MO-chloride VPE growth is thermodynamically controlled at vapor solid interface.
Experimental Calculated
-
5
.
.
0 0 0
-=
VPE system is regarded as the chloride VPE system rather than the MOVPE system. The ob-
—. -
215
I
I
2
4
I
I
6 8 lIE/V Ratio
References
I
10
This work was supported in part by a Scientific Research Grant-in-Aid for Priority-Area Research on “Photo-Excited Process” from the Mmistry of Education, Science and Culture of Japan.
12
Fig. 6. Comparison between the experimental and calculated growth rates as a function of the input Ill/V ratio.
[1] H. Okeda, M. Kamisawa, A. Koukitu and H. Seki, Japan. J. AppI. Phys. 29 (1990) L2149. [2] H. Seki and A. Koukitu, J. Crystal Growth 98(1989)118. [3] A. Koukitu, Y. Hasegawa, H. Seki and E. Schdnherr, J. Crystal Growth 98 (1989) ô97.
gallium and AsCl 3 has been made. The equilibrium partial pressures versus the input partial pressure of TEG, the reciprocal of substrate ternperatures and the input Ill/V ratio have been computed. The behavior of these equilibrium partial pressures shows the features of both the chloride VPE and the MOVPE systems. In particular, by paying attention to the predominant species in equilibrium, the cold-wall MO-chloride
[4] A. Koukitu and H. Seki, J. Crystal Growth 49 (1980) 325. [5] M. Yoshida and H. Watanabe. J. Electrochem. Soc. 132 (1985) 677. [6] A. Koukitu and H. Seki, Japan. J. AppI. Phys. 23 (1984) 74. [7] D.J. Kirwan, J. Electrochem. Soc. 117 (1970) 1572. [81A. Koukitu, T. Suzuki and H. Seki, J. Crystal Growth 74 (1986) 181. [9] G.B. Stringfellow, J. Crystal Growth 68 (1984) 111 [10] D.W. Shaw, in: Crystal Growth, Vol. 1, Ed. C.H.L. Goodman (Plenum, New York, 1978) p. 1.
Journal of Crystal Growth 1 1~(1991)211 215 North-Holland
Thermodynamic analysis of GaAs growth by cold-wall metalorganic-chloride vapor phase epitaxy Hitoshi Ikeda, Kenichi Saitoh, Yoshitugu Hasegawa, Akinori Koukitu and Hisashi Seki Department of Applied C/iconstrv. J~acnltvof Technology, Tokyo finn erlity of Agrcnltiue and ]echinologs, Koi~anei, IOk)o I~4,Japan
A thermodynamic analysis of cold wall MO chloride VPE growth of GaAs using triethylgallium and AsCI is described. The behavior of the equilibrium Partial pressures shows features ol both the chloride VP[ and the MOVPE systems. Fhe calculated growth rate is compared with the experimental data reported previously. The experimental growth rate as a function 01 the input partial pressure 01 TEG. the reciprocal of substrate temperatures and the input III V ratio are well explained by the thermodynamic model
1. Introduction Recently, we have reported the growth of GaAs using triethylgallium (TEG) and AsCI in a coldwall reactor [1].We call this method the cold-wall MO-chloride VPE. In the method, AsCl~is used as the arsenic source, instead of fatally toxic AsH which is used currently as the arsenic source in metalorganic vapor phase epitaxy (MOVPE). The reactor for the cold-wall MO-chloride VPE is almost the same as that for conventional MOVPE. Consequently, we can expect the same advantages as those of MOVPE. For example, it will have similar suitability for large-scale production and versatility as MOVPE, but without the use of hazardous source materials. In addition, it will be possible to grow aluminum-containing materials which are difficult to grow in chloride VPE. In previous papers [2,3], we have shown that thermodynamics provides useful information for the understanding of vapor phase epitaxy. While these studies clarified the thermodynamic characteristics of MOVPE, molecular beam epitaxy (MBE) and atomic layer epitaxy (ALE), those of the cold-wall MO-chloride VPE have not been studied yet. The purpose of this paper is to de-
with the experimental data. In order to calculate the equilibrium partial pressure, a previously developed computation method [41 has been applied to the growth system of the cold-wall MO-chloride VPE. It will be shown that the main features of the growth rate are explained by using the equilibrium model.
2. Calculation procedure The growth rate study on the cold-wall MOchloride VPE has shown that mass transport is the rate-determining step in the overall process [1]. This fact indicates that the rate of reaction is controlled simply by the rate of arrival of the growing species at the vapor solid interface. Under these conditions, we can assume that chemical equilibrium is established at the vapor solid interface, because the rate of chemical reaction is considered sufficiently high compared to the arrtval rate of reactants. The input TEG i’. decnmpnsed irreversihly according to the following homogeneous reaction near the vapor solid interface [5]: Ga(C,H.~)3(g)—s Ga(g) + 3 C7H4(g)
scribe a thermodynamic analysis of the cold-wall MO-chloride VPE and to compare the results 0022 0248 91 $03.50
1991
Elsevier Science Publishers By. All rights reserved
+
~H,(g). (1)
H. Ikeda et al
212
Thermodynamic anal~its of GaAs grovoh hi cold is all MO C hi/omide VPI
Since the input TEG is decomposed completely and the reverse reaction does not proceed, the ethylene (C,H4) in the products is considered as the inert gas in the present analysis. The following 9 Species arc chosen as the necessary vapor species in analysing the vapor growth of GaAs: GaCI, GaCl5, Ga, As4, As~, AsCl~,HCI, H~and C)H4. Other species which might possibly exist in the reaction system, Cl2, C2H4CI,. etc. were neglected. The chemical reactions which connect all the species at the vapor solid interface are: 2 GaCI(g) + ~As4(g) + H7(g) 2 GaAs(s) + 2 HCI(g),
(2)
2 Ga(g) + 2 HCI(g) GaCI(g) + 2 HCI(g)
(3) (4)
where ~ is the input partial pressure of TEG. Eq. (12) expresses the total pressure of the sys tem. Eq. (14) expresses that the deposition oceurs in the ratio of I to I for group Ill and group V elements. The equilibrium partial pressures at the va por solid interface can be obtained from the solution of the above simultaneous equations. The calculations were carried out by using a method similar to that developed previously [4]. The values of the equilibrium constants were the same as those in our previous papers [4.61,except that of eq. (II) [7].
3. Results and discussion
As 4kb/ ( \
‘~
2 GaCI(g) + H,(g), GaCI5(g) + l-I,(g),
As 2kb’’ ( ~\
(S\‘ ‘
AsCl~(g)+ ~H~(g)
.~As4(g)+ 3 HCI(g).
(6)
The equilibrium partial pressures of gaseous species over GaAs are shown in figs. I and 2. In the first figure, the tnput partial pressure of ‘lEG (P~)is set to the same partial pressure as that of the thermodynamic analysis of MOVPE process .
.
The equilibrium equations for these reactions are as follows: K1
P~(I/P(~(IP~,’Pit,.
(7)
K
P~,(P~/P(~~
(8)
K~ PG( I ~P1 /P(;( I P~
(9)
P11~5x10
100
.
III V
=
3
-
C2H4
-
K4
~atm H2
(10) (11)
P.~,/~A~,’ 1’A~4’ti( /P~ ~Pt~2
-
10
K, From the conservation constraint we have
-
As 2
i
+
Pfl
+
J(,~ç~ + Py,
+
P~~
1,
+
+
[(P~~,
i
+
~
(4PA, +
+
~
X (P11~~ + 2 Pit
~lEG
p(
~tt4’
~A,cI
+
~t t( I
+P11(~j
-
10
10
-
(13)
P~,,)
+
)
+
(12)
P(,,(i+3P~(i+3P\,(I
B
‘A~
PA~(i)j
15
500 ~.
GaCI3
-
(14) i~ -
-
I
600 100 Temperature °C
Fig I. The equilibriumtensperatule. partial pressures as
800 a function
of
H. Ikeda ci al.
/
Thermodynamic analy.os of GaAs growth by cold-wall MO chloride VPE
[2,3,8] for comparison. An interesting feature in
T = 650°C
these figures is that the partial pressures of GaCI, HCI, C2H4 and Ga are involved in the same figure. The former two species are the major vapor species in the chloride VPE system and the
10
U
213
P0° = 5x 10”~atm
_______________________________
H2
-
-
GaC
MOVPE system. Consequently, the cold-wall
latter twoinspecies dentally, MO-chloride the VPE present are system observed system, showscommonly C7H4 both features is anininert the of the chloride VPE and the MOVPE systems. Incigas and the partial pressure of Ga is low. If we neglect these species, the general features of the equilibrium partial pressures become quite similar to those of the chloride VPE system [ô]. Therefore, the cold-wall MO-chloride VPE system is regarded as the chloride VPE system rather than the MOVPE system. In the equilibrium model described above, the growth of the epitaxial layer is controlled by diffusion of the group III elements through the boundary layer [9]. According to Shaw [101, the growth rate under the mass transport type II or
~52HcI
E
I
-
10
10
-
_GaCL1 -
Ga -
- ____________ -
-
_)~~o 10
~
it
—~~i
02
06
I
1
2
~/v
4 Ratit
iii ii
6
10
20
Fig. 3. The equilibrium partial pressures as a function of the
T = 650~C 10
~
V
=
3
input 111 V ratio.
_________________________________
0
H2
-
10
diffusion limit at constant pressure is expressed as follows:
GaCI
rwhere kg is the mass transfer coefficient, P~1 (16) is the kg(P~~ttP111), input partial pressure of the group III element, and P~~1 is the equilibrium partial pressure at the substrate surface. In the cold-wall MOchloride VPE system for the GaAs growth,
~::~~AS~
1 O~10
r
kg[P~uo
~kg(P~EG
(FG,c+P(,( Pc’(I).
+P~,)]
(17)
Ga
AsCI3 10 10
10 P11~ (atm)
10
Fig. 2. The equilibrium partial pressures as a function of the input partial pressure of friethylgallium.
The last equation is obtained from P~act>> + P6~).Then we find again that the coldwall MO-chloride VPE system is regarded as the chloride VPE system, though it includes C2H4 and Ga species. Ftg. 3 shows the equtltbrium partial pressures over GaAs as a function of the 111/V ratio. At Ill/V 4, a drastic change of the partial pressures is seen. This is a remarkable feature gener-
214
H. Ikeda ci al.
Thermodynamic analprs of GaAs growth hi cold wall MO-chloride UPI
ally obtained in the cold-wall MO-chloride VPE system using AsCl~ as a chloride source. The broken line in the figure shows the vapor pressure of the liquid gallium. Therefore, we would have the deposition of a gallium droplet if the Ill/V ratio is larger than 4. Fig. 4 shows a comparison between the calculated growth rate and the experimental data. The experimental data are from our previous paper [I]. In the calculation of the growth rate, the value of k I’ was determined to be 2.77 X i0~ atm by adjusting to the experimental data of P~ 1.13 x 10 atm. It is seen that the agreement between the calculated and experimental growth rate is quite good. In fig. 5, a similar comparison is shown for the temperature dependence of the growth rate. Good agreement is obtained between the calculated and experimental growth rates, in the temperature range where the growth rate is nearly independent of deposition temperature. Therefore, we can conclude that mass transport is the rate-determining step in this temperature range. On the other hand, the experimental growth rate deviates from the calculated values at high tem-
/ I
•
0
/ ExperImental
—
/ /~
•
-
E
/
-
-
/ /0
0
5
.
—
Experimental Calculated
5
4
o
PnEG 15x10 atni tatm PA 1CI1 3,7500 mit TttalFlow:550m1
1 1.0
11 1000
Fig.
~.
12 T (K)
13
Comparison between the experimental and calculated
growth rates as a function of the reciprocal of temperature.
peratures. The surface morphology of the grown layers became hazy under these conditions. This may he attributable to the premature deposition of theofmetalorganic compound or the wall deposition GaAs. Finally, a comparison for the effect of the
Tni :650 C ~/V:4 Total Flow: 550m1 mm
/
‘ .
.
/ 0
// 0
/
/
0
.
larger than 4. Although some difference is oh served between the experimental and calculated growth rates, the general features of the experimental data are well explained by the calculation. The observed difference between the experimen tal and calculated growth rates is probably due to the fact that TEG is not sufficiently saturated in H gas in the experiment.
E
/
0
—
0/
.
-
I
o ~~
~ ~ 10
‘
500
I
I
tnput parttal pressure ratto between TEG and AsC1 5 on the growth rate is shown in fig. 6. The broken line in the calculated curve indicates that the deposition of a gallium droplet would he observed in the range because the Ill/V ratio is
Calculated
/ -~
I
/
• 10
100
Temperature ( C) 650 600 550
10
4atni
)
15
20
Pncu the ) xlO Fig. 4. Comparison between experimental and calculated growth iates as a function of the input partial pressure of triethylgallium
4. Conclusions A thermodynamic analysts of the cold-wall MO-chloride VPE growth of GaAs using triethyl-
H. Ikeda et al.
8
/ Thermodynamic analysis of GaAs growth by cold-wall MO-chloride VPE
I
0 0 —
-~
•
0
Acknowledgement
0 .
PxscI3 :2.51x10 4atm Tsuh :650 C Total Flow : 550 ml nile
0 0
served good agreement between the experimental and calculated growth rate shows that the reaction of the cold-wall MO-chloride VPE growth is thermodynamically controlled at vapor solid interface.
Experimental Calculated
-
5
.
.
0 0 0
-=
VPE system is regarded as the chloride VPE system rather than the MOVPE system. The ob-
—. -
215
I
I
2
4
I
I
6 8 lIE/V Ratio
References
I
10
This work was supported in part by a Scientific Research Grant-in-Aid for Priority-Area Research on “Photo-Excited Process” from the Mmistry of Education, Science and Culture of Japan.
12
Fig. 6. Comparison between the experimental and calculated growth rates as a function of the input Ill/V ratio.
[1] H. Okeda, M. Kamisawa, A. Koukitu and H. Seki, Japan. J. AppI. Phys. 29 (1990) L2149. [2] H. Seki and A. Koukitu, J. Crystal Growth 98(1989)118. [3] A. Koukitu, Y. Hasegawa, H. Seki and E. Schdnherr, J. Crystal Growth 98 (1989) ô97.
gallium and AsCl 3 has been made. The equilibrium partial pressures versus the input partial pressure of TEG, the reciprocal of substrate ternperatures and the input Ill/V ratio have been computed. The behavior of these equilibrium partial pressures shows the features of both the chloride VPE and the MOVPE systems. In particular, by paying attention to the predominant species in equilibrium, the cold-wall MO-chloride
[4] A. Koukitu and H. Seki, J. Crystal Growth 49 (1980) 325. [5] M. Yoshida and H. Watanabe. J. Electrochem. Soc. 132 (1985) 677. [6] A. Koukitu and H. Seki, Japan. J. AppI. Phys. 23 (1984) 74. [7] D.J. Kirwan, J. Electrochem. Soc. 117 (1970) 1572. [81A. Koukitu, T. Suzuki and H. Seki, J. Crystal Growth 74 (1986) 181. [9] G.B. Stringfellow, J. Crystal Growth 68 (1984) 111 [10] D.W. Shaw, in: Crystal Growth, Vol. 1, Ed. C.H.L. Goodman (Plenum, New York, 1978) p. 1.