Journal ArticleGax In1−xAs lattice matched to the InP substrate (x=0.47) has been grown by organometallic vapor phase epitaxy using trimethylindium (TMIn) and trimethylgallium (TMGa) as the group III sources and AsH3 as the As source. In a simple, horizontal, atmospheric pressure reactor, the GaInAs growth proceeds without visible evidence of parasitic prereaction problems. The process yields homogeneous, reproducible GaInAs with a high growth efficiency and a solid/vapor In distribution coefficient of nearly unity. Most importantly, several layers with room-temperature electron mobilities of approximately 10 000 cm2/Vs and carrier concentrations of approximately 1015 cm−3 have been produced. The 4-K photoluminescence shows a narrow (4-5 meV) band-edge emission peak and a low-intensity band acceptor peak at ~18 meV lower energy. Surface morphologies are routinely featureless as observed by high magnification interference contrast microscopy

Kuo, C.P.

Stringfellow, Gerald B.

English

The University of Utah: J. Willard Marriott Digital Library

Downloaded 10 Oct 2007 to 155.97.12.90. Redistribution subject to AIP license or copyright, see http://apl.aip.org/apl/copyright.jspOrganometallic vapor phase epitaxial growth of high purity GalnAs using trimethylindium c. P. Kuo, J. S. Yuan, R. M. Cohen, J. Dunn, and G. B. Stringfellow Departments of Materials Science and Engineering and Electrical Engineering, University of Utah, Salt Lake City, Utah 84112 (Received 16 November 1983; accepted for publication 19 December 1983) GaxlnI_xAs lattice matched to the InP substrate (x = 0.47) has been grown by organometallic vapor phase epitaxy using trimethylindium (TMln) and trimethylgallium (TMGa) as the group III sources and AsH3 as the As source. In a simple, horizontal, atmospheric pressure reactor, the Gain As growth proceeds without visible evidence of parasitic prereaction problems. The process yields homogeneous, reproducible GalnAs with a high growth efficiency and a solid/vapor In distribution coefficient of nearly unity. Most importantly, several layers with room-temperature electron mobilities of approximately 10 000 cm2 /V s and carrier concentrations of approximately 1015 cm- 3 have been produced. The 4-K photoluminescence shows a narrow (4-5 meV) band-edge emission peak and a low-intensity band acceptor peak at ~ 18 me V lower energy. Surface morphologies are routinely featureless as observed by high magnification interference contrast microscopy. PACS numbers: 68.55. + b, 73.60.Fw, 78.55.Ds, 68.60. + q GalnAs lattice matched to the InP substrate is one of the most promising new semiconductor materials. High electron mobility and peak velocity 1-3 and the ability to fab-ricate modulation-doped structures with InP4 make this al-loy ideal for ultrahigh-speed devices. The band gap of 0.75 e V (1.65 Jim) is ideal for the fabrication of detectors for fiber-optic systems operating in the optimum wavelength range of 1.3-1.5 Jim. s It has now been demonstrated that very high quality G!lo.47 111053 As can be grown with excellent properties by liquid phase epitaxy (LPE),6.7 hydride vapor phase epitaxy (HVPE),6.8 AsCl3 VPE (CIVPE),9 molecular beam epitaxy (MBE),10 and organometallic VPE (OMVPE).4.6 By each of these growth techniques, high room-temperature electron mobilities of;;;. 10 000 and 77 K electron mobilities of greater than 40000 cm2/Vs have been reported. OMVPE appears to be a promising technique for many applications requiring the growth of large quantities of ho-mogeneous, high quality material with multiple abrupt changes in composition and doping. II However, early re-sults indicated severe problems with gas phase reactions oc-curring upstream from the substrate, leading to low growth efficiency and inhomogeneous alloy composition. Such problems have been observed using various combinations of reactants; triethylgallium (TEGa) and triethylindium (TEln), 12 trimethylgallium (TMGa) and TEIn, 13 and TMGa and trimethylindium (TMln).I4 Duchemin and cowork-ers,4.IS have resorted to low pressure growth using TEGa and TEln group III sources. This has resulted in the only OMVPE grown Gao.47 Ina 53 As with electron mobilities of ;;;. 10000 cm2/Vs reported until now. Other groups have de-veloped adduct group III sources, such as TMln-TEP 16 and TMln-TMP 17 (TEP and TMP refer to triethyl and trimethyl phosphorus), which do not react upstream from the sub-strate to form In-containing polymers on the reactor walls. Since these adducts have low vapor pressures, this necessi-tates a slightly more complex apparatus, with all parts of the reactor downstream from the adduct source being heated to avoid condensation of the adduct on the walls. IX In addition, no high electron mobility GaOA7 In053 As has been reported to date. Recently, the growth of In-containing Ill/V com-pounds and alloys using TMln at one atmosphere pressure has been reinvestigated. Possibly because of the higher puri-ty of todays TMln, two groups have independently found that no predeposition problems are observed. Sacilotti et al. I ,! and Hsu et al. 20 have reported the growth of InP with electron mobilities of approximately 3500 cm2/Vs, as com-pared with the highest values of > 5000 cm2 /V s reported for growth using TEln in a low pressure system.4 Ga0 .47 In053 As alloys have also been successfully grown using TMln by Sa-cilotti et al. 21 and by Kuo et a/. I2 In the former case no mobil-ity values were reported. Kuo et al. I2 reported low values of electron mobility due to the high doping level of 3 X 1017 cm- 3 . In this letter we describe the growth and properties of the first high purity Gaa.47 Ino.53 As to be grown by OMVPE at atmospheric pressure using TMln, TMGa, and AsH,. Room-temperature electron mobilities of ~ 10 000 cm2 /V s have been obtained repreatedly. The 4-K photolumines-cence (PL) shows a single, sharp, near-band-edge emission peak with a much less intense peak at ~ 18 me V lower ener-gy. The featureless surface morphology and sharp x-ray dif-fraction peaks (within the resolution limits of conventional x-ray measurements) are also indicative of the excellent ho-mogeneity and high structural quality of the material. The atmospheric pressure, horizontal, IR heated OMVPE system used in this study was described previous-ly.l2 The solid TMln (obtained from Alpha/Ventron) was held in a temperature controlled bath at 10 °C and the TMGa was held at - 11.5 dc. The purified H2 flow rates through the two sources were 120 sccm and 0.9 sccm, respec-tively. The AsH3 (diluted to 10% in H2) flow rate was 60 sccm. These conditions give a growth rate of 0.05 Jim/min. The (I (0) oriented InP substrates were prepared using a 4-min 5: I : I A etch prior to introduction into the reactor. 550 Appl. Phys. Lett. 44 (5), 1 March 1984 0003-6951/84/050550-03$01.00 © 1984 American Institute of Physics 550 Downloaded 10 Oct 2007 to 155.97.12.90. Redistribution subject to AIP license or copyright, see http://apl.aip.org/apl/copyright.jspPreliminary results IZ indicated that good morphology GIIo.47 1110.53 As could be obtained only at low growth tem-peratures of below 550 DC, presu1Dably due to P loss from the substrate during heat-up in the Hz + AsH3 atmosphere. Even though the PL is found to be strong under such condi-tions, it is apparently due to recombination through the car-bon acceptor level rather than to free and bound exciton recombination. The 300-K electron mobility was also found to be less than 3500 cmz /Vs. The impurity contamination was found to decrease with increasing growth temperature, but the surface morphology was found to deteriorate. To solve this problem, a two-step growth procedure was adopt-ed. First, a very thin (- 1000 A.) layer of GIIo.47 In053 As is grown at a temperature of 540 DC. Then, the temperature is rapidly increased to 650 DC where the 1-2-Jlm Gao.47 In053 As layer is grown. This results in reproducibly excellent results. For a series of 20 runs, every surface was found to be mirror smooth to the naked eye and to have no observable features upon examination at high magnification using interference contrast microscopy. The degree oflattice match and structural perfection of the layers were investigated using conventional x-ray dif-fraction measurements. The (400) diffraction results are il-lustrated by the examples shown in Fig. 1. These samples were chosen because the substrate and epilayer peaks could be readily distinguished. Other samples are so closely lattice matched that the epilayer and substrate peaks are indistin-guishable. Typically, Lta(/ao<2X 10- 3. It is seen that the diffraction peaks from the substrate are nearly the same width as those from the substrate. Both are within the resolu-tion limit of the conventional x-ray diffractometer. A sample 4-K PL spectrum obtained at an excitation intensity of approximately 10 W /cm2 from the 4880-A. Ar laser line is shown in Fig. 2. The spectrum is dominated by the narrow peak at 0.8138 eV which has a half-width of 4.5 meV. This is very similar to the peak observed by Goetz et al. 6 in high quality LPE and OMVPE GlIo47 In053 As, which #126 (400) 63 28 # 127 (400) ~l (12 epl sub tl1 ( 2 ) i j I 63 64 28 FIG. I. 1400) x-ray diffraction spectra for two samples of Gain As grown on InP substrates. These samples were chosen because substrate and epilayer peaks could be clearly distinguished. 551 Appl. Phys. Lett. Vol. 44. No.5. 1 March 1984 w U Z w ~ Z ~ :0 <5 o &= 0.8138 eV I ~~~~ __ ~~~ __ ~~~~~ __ ~ __ ~ __ -L~.~ 1.50 1.51 1.52 1.53 1.54 1.55 1.56 1.57 1.58 1.59 1.60 1.61 A IlL m) FIG. 2. Liquid helium temperature photoluminescence spectrum for a sam-ple of Ga" 47 Ino 5' As grown on an InP substrate. The excitation intensity was \0 W fcm'. The detector was a Ge pin cooled to 77 K. is attributed to a combination of several free and bound exci-ton peaks which cannot be resolved. Goetz et a/. found the PL peak to occur at 0.808 eV for precisely lattice-matched layers. For a series of runs made under conditions specified above, the position of this peak was found to vary between 0.807 and 0.817 eV, which is a variation in composition of only Ltx = ± 0.004. This indicates the remarkable degree of composition control obtained using this process. A small peak is observed at approximately 0.018 e V lower energy than the main peak. The results of Goetz et al. 6 indicate that this may be due to Zn. Pearsall et al. 23 reported the Zn ionization energy to be 19 me V from hole freeze-out experiments. A peak located at an energy 40--45 meV below the main peak is also sometimes observed. A notable feature of these spectra is the absence of any carbon related peak. Apparently the carbon concentration in G<L In As -047 0.53 grown using trim ethyl source materials is low for growth temperatures of 650 DC. Earlier results l2 indicated that at 540 DC, carbon was a major source of contamination. As will :> ..... N E ~ >->- 10 4 :::; ;i; 0 ::i' z 0 '" >-u UJ -' UJ 2xl0 3 ~ 60 100 200 300 400 T (OK) FIG. 3. Electron mobility vs temperature for several samples of Ga,'.47 Inol3 As grown on semiinsulating InP substrates at temperatures of 650·C (0 ••• 6 . • ) and 540·C (0). Kuo eta/. 551 Downloaded 10 Oct 2007 to 155.97.12.90. Redistribution subject to AIP license or copyright, see http://apl.aip.org/apl/copyright.jspbe seen, this is consistent with the electrical properties of the layers grown at 540·C in contrast with those grown at 650·C. The electrical properties of these undoped GauA7 Ina.53 As layers, which are all 1.0--2.0!lm thick, are summarized in Fig. 3. The carrier concentrations are repro-ducibly approximately 1015 cm- 3. The 300-K mobilities range from 7500 to 10 000 cm2/Vs, and the 77-K mobilities are in the range from 30 000 to 40 000cm2/Vs. The tempera-ture dependence of mobility is qualitatively as expected for a combination of optical phonon and ionized impurity scatter-ing. It should be noted that these are the first room-tempera-ture electron mobilities in the 10 000-cm2/Vs range to be reported for layers grown using TMIn, either by itself or in adduct form. The GaOA7 Ino53 As layers grown at 540·C have lower mobilities. As seen in Fig. 3, they show the T - 1/2 temperature dependence previously attributed to scattering by carbon in GaAs and AIGaAs samples. 22 It should be not-ed that this sample was grown using TMAs rather than AsHl • In summary, the quality of GaOA7 Ino.53 As grown by OMVPE using TMIn in an atmospheric pressure reactor is shown to be excellent with properties similar to those of the best samples produced by LPE, HVPE, CIVPE, MBE, or low pressure OMVPE using TEIn. The key growth param-eter leading to the high material quality is the relatively high substrate temperature of 650 ·C. To avoid morphological problems apparently associated with the decomposition of the InP substrate, a very thin layer of GaOA7 Ino53 As is grown at 540 ·C before the substrate temperture is increased to 650 ·C. This procedure has produced a number of epi-layers with excellent surface morphologies, narrow x-ray diffraction linewidths, 4-K PL spectra dominated by a sin-gle, narrow, exciton-related line, and room-temperature electron mobilities of -10 000 cm2/Vs. This work was supported by the Army Research Office, contract number DAAG29-83-K-OlS3. The authors wish to 552 Appl. Phys. Lett., Vol. 44, No.5, 1 March 1984 express their appreciation to Mr. Harry Jen for assisting with the van der Pauw measurements. Iy. Takeda, in GalnAsP Alloy Semiconductors, edited by T. P. Pearsall (Wi-ley, Chichester, 1982), pp. 213-241. 2M. A. Littlejohn, T. H. Glisson, and 1. R. Hauser, in GalnAsP Alloy Semi-conductors, edited by T. P. Pearsall (Wiley, Chichester, 1982), pp. 243-275. 'T. H. Windhom, 1. W. Cook, and G. E. Stillman, 1. Electron. Mater. 11, 1065 (1982). 4M. Razeghi, M. A. Poisson, 1. P. Larivain, and 1. P. Duchemin, 1. Elec-tron. Mater. 12, 371 (1983). 'Yo Matsushima and K. Sakai, in GalnAsP Alloy Semiconductors, edited by T. P. Pearsall (Wiley, Chichester, 1982), pp. 413--436. OK. H. Goetz, D. Bimberg, H. Jurgensen, 1. Selders, A. V. Solomonov, G. F. Glinskii, and M. Razeghi, J. App\. Phys. 54.4543 (1983). 71. D. Oliver and 1. F. Eastman, 1. Electron. Mater. 9, 693 (1980). "S. T. lolly, S. Y. Narayan, J. P. Packowski, and D. Capewell, SPIE Proc. 323,74 (1982). 9J. Komeno, M. Takikawa, K. Kodama, and M. Ozeki, Paper Q-6 present-ed at the Electronic Materials Confemece, Burlington, Vermont, June 22-24, 1983. IOD. Bonnevie and D. Huet, 1. de Physique C 5, 445 11982). "G. B. Stringfellow, in Semiconductors and Semimeta/s, edited by W. Tsang Ito be published). 12C. P. Kuo, R. M. Cohen, and G. B. Stringfellow, 1. Cryst. Growth (to be published). "1. P. Noad and A. J. SpringThorpe, 1. Electron. Mater. 9, 601 (1980). 14R. H. Moss (private communication). "1. P. Duchemin, 1. P. Hirtz, M. Razeghi, and M. Bonnet, Inst. Phys. Conf. Ser. 63, 89 (1981). lOR. H. Moss and 1. S. Evans, J. Cryst. Growth 55, 129 (1981). 17K. W:Benz, H. Renz, J. Weidlein, and M. H. Pilkuhn, 1. Electron. Mater. 10,18511981); K. W. Benz, H. Haspeklo, and R. Bosch, J. de Physique C 5, 393 (1982). '"A. K. Chatterfee, M. M. Faktor, R. J. Moss, and E. A. D. White, 1. de Physique C 5, 491 (1982). 19M. Sacilotti, A. Mircea, and R. Azoulay, J. Cryst. Growth 63, 111 (1983). 2[)c. C. Hsu, R. M. Cohen, and G. B. Stringfellow, 1. Cryst. Growth 63, 8 11983). "M. Sacilotti, A. Mircea, R. Azoulay, and K. Rao, Paper C-1 presented at the Electronic Materials Conference, Burlington, Vermont, June 22-24, 1983. 22G. B. Stringfellow, J. App\. Phys. 36,540 11980). 2'T. P. Pearsall, 1. Eaves, and 1. C. Portal, 1. App\. Phys. 54, \03711983). Kuo etal. 552 

Organometallic vapor phase epitaxial growth of high purity GaInAs using trimethylindium

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Organometallic vapor phase epitaxial growth of high purity GaInAs using trimethylindium

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