Eqilibrium Analysis of the TMGa-TMA1-AsH 3 -H 2 Mocvd Epitaxial Growth System
- PDF / 385,815 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 93 Downloads / 156 Views
EQILIBRIUM ANALYSIS OF THE TMGa-TMA1-AsH 3 -H 2 MOCVD EPITAXIAL GROWTH SYSTEM HYUK J. MOON AND THOMAS G. STOEBE Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195 BRIAN K. CHADWICK United Epitaxial Technologies, Inc., 19545 N.W. Von Neumann Drive, D4/210, Beaverton, OR 97006 ABSTRACT The thermodynamic equilibrium state of the Ga-Al-As-C-H system was determined theoretically by means of an iterative equilibrium constant method. This method of calculation Is presented and discussed. With very little operator input, the program is capable of computing the partial pressures of the gas-phase species present in the equilibrated system. In these calculations the system was considered to be saturated with solid-phase A1GaAs and included 58 plausible gas-phase intermediates which evolved from the initially present gas species; trimethylgallium, trimethylaluminum, arsine, and hydrogen. Temperature and total system pressure ranges investigated were 750-1100 K and 0.1 atm-1.0 atm, respectively. The effects of temperature and pressure variations, in addition to effects caused by changes in the appropriate atom ratios, have been delineated. The properties of this equilibrated system are compared with those from recent thermodynamic research efforts on AlGaAs systems consisting of only gaseous constituents. INTRODUCTION Several important compound semiconductor epitaxial layer growth techniques have been introduced, some of which are currently being employed for the production of device quality materials; among these are Liquid Phase Epitaxy (LPE), Vapor Phase Epitaxy (VPE), Metalorganic Chemical Vapor Deposition (MOCVD), Molecular Beam Epitaxy (MBE), etc. MOCVD has demonstrated the ability to grow high quality epitaxial layers, however, understanding and controlling the numerous parameters associated with the MOCVD processes is difficult. Thermodynamic analyses provide useful information needed for additional understanding of the MOCVD growth process. It has been shown that thermodynamic analyses can help predict alloy compositions and maximum growth rates in MOCVD systems [1,21. Although epitaxial growth by MOCVD is generally regarded as a kinetically controlled process, since the rates of chemical reactions at the growth surface are high compared to the arrival rate of reactants to the growth surface, we may assume that a near-thermodynamic equilibrium is established at the growth surface. This study is intended to delineate the chemical thermodynamic equilibrium state of an MOCVD system when saturated with undoped AlGaAs solid. Han and Rao 131 have used the iterative equilibrium constant method to compute the equilibrium state of the Ga-As-H-Cl VPE growth system. Rao [41 and Chadwick [5] have described the iterative approach in detail for other systems. Chadwick [61 has used the iterative equilibrium constant method to describe the equilibrium state of a system with undoped GaAs Mat. Res. Soc. Symp. Proc. Vol. 131.
1989 Materials Research Society
124
solid. A similar analysis was p
Data Loading...
