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OMVPE growth of GaInP
648
Journal of Crystal Growth 62(1983) 648—650 North-Holland Publishing Company
PRIORITY COMMUNICATION
OMVPE GROWTH OF GatnP C.C. HSU, R.M. COHEN and G.B. STRINGFELLOW University of Utah, Salt Lake Cits’, Utah 84112. USA Received 30 May 1983
Excellent photoluminescent quality Ga In 1 -- P with x 0.5 has been grown epitaxially on GaAs substrates using OMVPE. The source materials used were trimethylgallium. trimethylindium and phosphine in an H2 ambient. At the optimum temperature of 625°C and a V/Ill ratio of 40, high photoluminescence efficiency and narrow half-widths were obtained.
Ga~In1~Phas been studied as a material for visible LEDs and injection lasers for more than a decade [1,2]. The alloy with x 0.5 is latticematched to the GaAs substrate and has a band gap of 1.9 eV. High quality Ga0 51n() 5P alloys have been grown by the conventional liquid phase epitaxy (LPE) [1—5] and chloride vapor phase epitaxy (VPE) [6—81techniques. Only Yoshino et al. [9] have reported on the organometallic vapor phase epitaxial (OMVPE) growth of Ga~In1~P in a low pressure reactor using triethylgallium (TEGa), triethylindum (TEIn) and phosphine. In this work, we report improved results using tnmethylindium (TMIn) and trimethylgallium (TMGa) with phosphine, in an atmospheric pressure reactor. The simple horizontal reactor has a cross section offor2 the cm group high by cmgroup wide. VSeparate tubes III 5and reactantsinlet are
composition control and homogeneity in Ill/V alloys. As a result several groups [9,13] have adopted the use of low pressure OMVPE reactors. In this way the gasses flow through the reactor so fast that they do not have sufficient time for the polymer forming reactions to occur before they reach the heated substrate. An alternate approach has been to use non-polymer-forming adducts as In sources [15,16]. In our experience, TMIn is much less likely to participate in polymer forming reactions than TEIn. Thus we have adopted the use of TMIn in an atmospheric pressure reactor with good results. We have been able to grow InP at temperatures between 550 and 700°Cwith excellent morphology and photoluminescence (PL) efficiency. The doping 3level is found to be in the the growth low 1014efficiency to l015 range. In addition, cm (growth rate/TMIn molar flow rate) is found to
used. IR from a focussed lamp is used to heat the graphite susceptor [10]. The plumbing is all stainless steel with welded joints where practical, automatic flow controllers on all lines, and air actuated bellows valves throughout. The reactor is operated at I atm pressure. OMVPE growth results for In containing cornpounds [11—l3] and alloys [14], indicate that TMIn and especially TEIn react with AsH 3 or PH3 in the gas phase upstream from the substrate to produce a nonvolatile polymer on the reactor walls. This resulted in very low growth rates and very poor
be high, 6.9 x l0~p.m/mole, as compared to 4.5 X 102 p.m/mole using TEIn in a low pressure reactor [13]. This value of growth efficiency is based on a TMIn vapor pressure of I Torr at 17°C as measured in our laboratory [17]. Stringfellow [18] has tabulated the growth efficiency from published results for many systems. A value of 6.9 x i03 p.m/mole indicates a complete absence of the
0022-0248/83/0000--0000/$03.00
©
parasitic reaction to form polymers on the reactor walls upstream from the substrate. Ga~In1~P with x~0.5, the GaAs latticematching composition, has been grown using an
1983 North-Holland
C.C. Hsu et a!.
/
OM VPE growth of GainP
H2 flow rate through the TMIn, held at 17°C,of 150 sccm, an H2 flow rate through the TMGa, held at 12°C,of 3 seem, a flow rate of 10% PH3 diluted in H2 of either 100 or 300 seem and a total H 2 flow rate of 2 liters/mm. The growth temperature was found to be the most important growth parameter for obtaining good morphology and PL quality, providing that high V/Ill ratios and proper substrate preparation procedures were used. The (100)GaAs substrates were etched in 6: 1: 1 H2S04, H202, H20 just prior to introduction into the reactor. Using these conditions a typical growth rate for Ga0 51n0 5P was 5 p.m/h. Extremely smooth surfaces, as examined by high resolution Nomarski interference contrast microscopy, were obtained only at substrate temperatures of between 600 and 650°C.The composition —
-
649
was found to be virtually independent of growth temperature, as shown in fig. 1. The composition was also found to be uniform to within a few 2 substrate percent over the approximately 2 cm area. These observations support the contention that little, if any, parasitic In predeposition occurs. The PL intensity is found to be strongly dependent on substrate temperature, as shown in fig. 2. The optimum temperature appears to be approximately 625°C,where the PL intensity is cornparable to the best InP observed in our laboratory. The PL half-width also indicates that the best quality material is grown in the temperature range of 600 to 650°C. The room temperature PL halfwidths of 41 meV are considerably better than those reported by Yoshino et al. [9] and are close to the 38 meV (1.5 kT) observed in lowly doped
CamP
i0~
4
$
4
~I0-
IO~-
200-
160
.~E
-
10
-
____
575
600
625
650
615
Growth Tempera lure (DC) Fig. 1. Ga~In1 ~P composition, x, and 300 K photoluminescerice half-width versus growth temperature. Other experimental conditions were fixed at values given in the text.
515
I
I
I
600
625
650
615
Growth Temperature 1C) Fig. 2. Photoluminescence intensity (relative scale) measured at 300 K versus substrate temperature for Ga~ln1~P with x 0.5.
650
CC. Hsu ci a!.
/
OMVPE growth of GaInP
InP [19]. The best LPE Ga0 5In05P layers have PL half-widths of 37—45 meV [3—5].The best reported chloride VPE Ga05In05P half-width is 45 meV [6], although for GaInAsP alloys, 38 meV halfwidths have been reported [8]. The observation that as the half-width increases, the PL intensity decreases is similar to results observed in chloride VPE systems [7]. The second important growth parameter is the V/Ill ratio in the input gas stream. In fig. 3 the PL intensity and half-width are both plotted versus V/Ill ratio. Minimum values of approximately 40 are necessary to achieve the best surface morphology, PL intensity, and PL half-width. Under the optimum growth conditions, the carrier 3 and conthe centration is approximately lOIS cm room temperature electron mobility is on the order of 1000 cm2/V. s. In conclusion, the OMVPE growth of InP and Ga 05In05P using TMIn, TMGa and PH3 has
The authors gratefully acknowledge the support of Instrument for this TheGeneral continued interest Corporation of Ted Larsen and work. L.R. Hill are particularly appreciated.
References [1] G.B. Stringfellow. J. AppI. Phys. 43 (1972) 3455. [21G.B. Stringfellow, P.F. Lindquist and R.A. Burmeister, J. Electron. Mater. 1(1972) 437.
ID C
[3] H. Kawanishi, M. Hiraoka, K. Yoshioka, K. Nishio. T. Nakagomi. and S. Tanaka, Electron. Letters 18 (1982) 385. 141 H. Asai and K. Oe. J. Appl. Phys. 53 (1982) 6849. I
T;
/ / /
62
C
1 , 6o~
/
102
IO~
been successfully carried out in a simple, atmospheric pressure reactor with no evidence of parasitic In prereaction problems. The optimum conditions for the growth of Ga0 5In0 5P lattice-matched to the GaAs substrate are found to include a V/Ill ratio of 40 (or larger) and a growth temperature of between 600 and 650°C. The resultant Ga~5In05Phas a perfectly smooth surface morphology. high PL intensity (comparable to high quality InP) and the narrowest room temperature PL half-width reported to date for OMVPE grown material.
/
/ / / / / V / / // // / / /
-
[5] H. Kyuragi. A. Suzuki, S. Matsumura and H. Matsunami. AppI.Nuese, Phys. Letters 37 (1980) 723. [61 C.J. A.G. Sigai. MS. Abrahams and J.J. Gannon. J. Electrochem. Soc. 7 (1973) 956. [7] A.G. Sigai, C.J. Nuese, R.E. Enstrom and T. Zamerowski, J. Electrochem. Soc. 7 (1973) 947. [8] G.H. Olsen and T.J. Zamerowski, Progr. Crystal Growth Characterization 2 (1979) 309. Yoshino, T. Iwamoto and H. Kukimoto. J. Crystal
[91J.
Growth 55 (1981) 74. [10] H. Beneking, A. Escobosa and H. Krautle, J. Electron. Mater. 10 (1981) 473. [11] H.M. Manasevit and WI. Simpson. J. Electrochem. Soc. 120 (1973) 135. [12] T. Fukui and Y. Horikoshi. Japan. J. AppI. Phys. 19 (1980) L395. [131 M. Razeghi. M.A. Poisson. J.P. Larivain and J.P. Duche-
I
80
-
~ 40
-
+
C 625~
I
I
I
I
II
20
30
40
C
V/ffl RatIo Fig. 3. Photoluminescence intensity (relative scale) and spectral half-width, both measured at 300 K, versus V/Ill ratio in the input gas stream for Ga ,In I P with x 0.5.
nsin. J. Electron. Mater. 12 (1983) 371. [14] J.P. Noad and A.J. Springthorpe, J. Electron. Mater. 9 (1980) 601. [15] K.W. Benz, H. Renz, J. Weidlein and M.H. Pilkuhn, J. Electron. Mater. 10 (1981) 185. [161 R.H. Moss and J.S. Evans. J. Crystal Growth 55(1981) 129. [171 C. Larsen and G.B. Stringfellow. unpublished results.
]18l G.B. Stringfellow. in: Semiconductors and Semimetals. to be published. [19] CC. Usu. R.M. Cohen and G.B. Stringfellow, to be published.
Journal of Crystal Growth 62(1983) 648—650 North-Holland Publishing Company
PRIORITY COMMUNICATION
OMVPE GROWTH OF GatnP C.C. HSU, R.M. COHEN and G.B. STRINGFELLOW University of Utah, Salt Lake Cits’, Utah 84112. USA Received 30 May 1983
Excellent photoluminescent quality Ga In 1 -- P with x 0.5 has been grown epitaxially on GaAs substrates using OMVPE. The source materials used were trimethylgallium. trimethylindium and phosphine in an H2 ambient. At the optimum temperature of 625°C and a V/Ill ratio of 40, high photoluminescence efficiency and narrow half-widths were obtained.
Ga~In1~Phas been studied as a material for visible LEDs and injection lasers for more than a decade [1,2]. The alloy with x 0.5 is latticematched to the GaAs substrate and has a band gap of 1.9 eV. High quality Ga0 51n() 5P alloys have been grown by the conventional liquid phase epitaxy (LPE) [1—5] and chloride vapor phase epitaxy (VPE) [6—81techniques. Only Yoshino et al. [9] have reported on the organometallic vapor phase epitaxial (OMVPE) growth of Ga~In1~P in a low pressure reactor using triethylgallium (TEGa), triethylindum (TEIn) and phosphine. In this work, we report improved results using tnmethylindium (TMIn) and trimethylgallium (TMGa) with phosphine, in an atmospheric pressure reactor. The simple horizontal reactor has a cross section offor2 the cm group high by cmgroup wide. VSeparate tubes III 5and reactantsinlet are
composition control and homogeneity in Ill/V alloys. As a result several groups [9,13] have adopted the use of low pressure OMVPE reactors. In this way the gasses flow through the reactor so fast that they do not have sufficient time for the polymer forming reactions to occur before they reach the heated substrate. An alternate approach has been to use non-polymer-forming adducts as In sources [15,16]. In our experience, TMIn is much less likely to participate in polymer forming reactions than TEIn. Thus we have adopted the use of TMIn in an atmospheric pressure reactor with good results. We have been able to grow InP at temperatures between 550 and 700°Cwith excellent morphology and photoluminescence (PL) efficiency. The doping 3level is found to be in the the growth low 1014efficiency to l015 range. In addition, cm (growth rate/TMIn molar flow rate) is found to
used. IR from a focussed lamp is used to heat the graphite susceptor [10]. The plumbing is all stainless steel with welded joints where practical, automatic flow controllers on all lines, and air actuated bellows valves throughout. The reactor is operated at I atm pressure. OMVPE growth results for In containing cornpounds [11—l3] and alloys [14], indicate that TMIn and especially TEIn react with AsH 3 or PH3 in the gas phase upstream from the substrate to produce a nonvolatile polymer on the reactor walls. This resulted in very low growth rates and very poor
be high, 6.9 x l0~p.m/mole, as compared to 4.5 X 102 p.m/mole using TEIn in a low pressure reactor [13]. This value of growth efficiency is based on a TMIn vapor pressure of I Torr at 17°C as measured in our laboratory [17]. Stringfellow [18] has tabulated the growth efficiency from published results for many systems. A value of 6.9 x i03 p.m/mole indicates a complete absence of the
0022-0248/83/0000--0000/$03.00
©
parasitic reaction to form polymers on the reactor walls upstream from the substrate. Ga~In1~P with x~0.5, the GaAs latticematching composition, has been grown using an
1983 North-Holland
C.C. Hsu et a!.
/
OM VPE growth of GainP
H2 flow rate through the TMIn, held at 17°C,of 150 sccm, an H2 flow rate through the TMGa, held at 12°C,of 3 seem, a flow rate of 10% PH3 diluted in H2 of either 100 or 300 seem and a total H 2 flow rate of 2 liters/mm. The growth temperature was found to be the most important growth parameter for obtaining good morphology and PL quality, providing that high V/Ill ratios and proper substrate preparation procedures were used. The (100)GaAs substrates were etched in 6: 1: 1 H2S04, H202, H20 just prior to introduction into the reactor. Using these conditions a typical growth rate for Ga0 51n0 5P was 5 p.m/h. Extremely smooth surfaces, as examined by high resolution Nomarski interference contrast microscopy, were obtained only at substrate temperatures of between 600 and 650°C.The composition —
-
649
was found to be virtually independent of growth temperature, as shown in fig. 1. The composition was also found to be uniform to within a few 2 substrate percent over the approximately 2 cm area. These observations support the contention that little, if any, parasitic In predeposition occurs. The PL intensity is found to be strongly dependent on substrate temperature, as shown in fig. 2. The optimum temperature appears to be approximately 625°C,where the PL intensity is cornparable to the best InP observed in our laboratory. The PL half-width also indicates that the best quality material is grown in the temperature range of 600 to 650°C. The room temperature PL halfwidths of 41 meV are considerably better than those reported by Yoshino et al. [9] and are close to the 38 meV (1.5 kT) observed in lowly doped
CamP
i0~
4
$
4
~I0-
IO~-
200-
160
.~E
-
10
-
____
575
600
625
650
615
Growth Tempera lure (DC) Fig. 1. Ga~In1 ~P composition, x, and 300 K photoluminescerice half-width versus growth temperature. Other experimental conditions were fixed at values given in the text.
515
I
I
I
600
625
650
615
Growth Temperature 1C) Fig. 2. Photoluminescence intensity (relative scale) measured at 300 K versus substrate temperature for Ga~ln1~P with x 0.5.
650
CC. Hsu ci a!.
/
OMVPE growth of GaInP
InP [19]. The best LPE Ga0 5In05P layers have PL half-widths of 37—45 meV [3—5].The best reported chloride VPE Ga05In05P half-width is 45 meV [6], although for GaInAsP alloys, 38 meV halfwidths have been reported [8]. The observation that as the half-width increases, the PL intensity decreases is similar to results observed in chloride VPE systems [7]. The second important growth parameter is the V/Ill ratio in the input gas stream. In fig. 3 the PL intensity and half-width are both plotted versus V/Ill ratio. Minimum values of approximately 40 are necessary to achieve the best surface morphology, PL intensity, and PL half-width. Under the optimum growth conditions, the carrier 3 and conthe centration is approximately lOIS cm room temperature electron mobility is on the order of 1000 cm2/V. s. In conclusion, the OMVPE growth of InP and Ga 05In05P using TMIn, TMGa and PH3 has
The authors gratefully acknowledge the support of Instrument for this TheGeneral continued interest Corporation of Ted Larsen and work. L.R. Hill are particularly appreciated.
References [1] G.B. Stringfellow. J. AppI. Phys. 43 (1972) 3455. [21G.B. Stringfellow, P.F. Lindquist and R.A. Burmeister, J. Electron. Mater. 1(1972) 437.
ID C
[3] H. Kawanishi, M. Hiraoka, K. Yoshioka, K. Nishio. T. Nakagomi. and S. Tanaka, Electron. Letters 18 (1982) 385. 141 H. Asai and K. Oe. J. Appl. Phys. 53 (1982) 6849. I
T;
/ / /
62
C
1 , 6o~
/
102
IO~
been successfully carried out in a simple, atmospheric pressure reactor with no evidence of parasitic In prereaction problems. The optimum conditions for the growth of Ga0 5In0 5P lattice-matched to the GaAs substrate are found to include a V/Ill ratio of 40 (or larger) and a growth temperature of between 600 and 650°C. The resultant Ga~5In05Phas a perfectly smooth surface morphology. high PL intensity (comparable to high quality InP) and the narrowest room temperature PL half-width reported to date for OMVPE grown material.
/
/ / / / / V / / // // / / /
-
[5] H. Kyuragi. A. Suzuki, S. Matsumura and H. Matsunami. AppI.Nuese, Phys. Letters 37 (1980) 723. [61 C.J. A.G. Sigai. MS. Abrahams and J.J. Gannon. J. Electrochem. Soc. 7 (1973) 956. [7] A.G. Sigai, C.J. Nuese, R.E. Enstrom and T. Zamerowski, J. Electrochem. Soc. 7 (1973) 947. [8] G.H. Olsen and T.J. Zamerowski, Progr. Crystal Growth Characterization 2 (1979) 309. Yoshino, T. Iwamoto and H. Kukimoto. J. Crystal
[91J.
Growth 55 (1981) 74. [10] H. Beneking, A. Escobosa and H. Krautle, J. Electron. Mater. 10 (1981) 473. [11] H.M. Manasevit and WI. Simpson. J. Electrochem. Soc. 120 (1973) 135. [12] T. Fukui and Y. Horikoshi. Japan. J. AppI. Phys. 19 (1980) L395. [131 M. Razeghi. M.A. Poisson. J.P. Larivain and J.P. Duche-
I
80
-
~ 40
-
+
C 625~
I
I
I
I
II
20
30
40
C
V/ffl RatIo Fig. 3. Photoluminescence intensity (relative scale) and spectral half-width, both measured at 300 K, versus V/Ill ratio in the input gas stream for Ga ,In I P with x 0.5.
nsin. J. Electron. Mater. 12 (1983) 371. [14] J.P. Noad and A.J. Springthorpe, J. Electron. Mater. 9 (1980) 601. [15] K.W. Benz, H. Renz, J. Weidlein and M.H. Pilkuhn, J. Electron. Mater. 10 (1981) 185. [161 R.H. Moss and J.S. Evans. J. Crystal Growth 55(1981) 129. [171 C. Larsen and G.B. Stringfellow. unpublished results.
]18l G.B. Stringfellow. in: Semiconductors and Semimetals. to be published. [19] CC. Usu. R.M. Cohen and G.B. Stringfellow, to be published.