Model Systems for the Epitaxial Growth and Capping of GaAs
Abstract
A computer program has been written for the CVD of epitaxial GaAs and InP in a three bubbler, two boat silica glass reactor using the Ga/AsCl3/H2 and In/PCl3/H2 techniques, respectively. The data bank contains the most recent enthalpy and free energy values. The latter are in the form of polynomials and, where necessary, recalculated from heat capacity or spectroscopic data. The importance of correct enthalpy values for computing As2/As4 ratios and the concentrations of volatile silicon compounds is discussed in detail. Calculations were made by iterative approximations rather than using the minimized total Gibb's free energy method. The difference in these methods is examined. The chemistry of the transport system has been examined in stages in the high temperature source region. Three models are proposed for the flat profile reaction of HCl with the arsenic saturated source material which is covered by a crust of GaAs (or InP). In model I HCl reacts only with GaAs. In Model II a series of reactions occur resulting in constant crust throughout the growth period. Additional reactions occur when there is a temperature gradient in the source. Actual experimental data for Ga/As ratios corresponds to a combination of these models. The effect of AsCl3 input, H2-inert gas carrier mixtures and the addition of H2O, O2, and NH3 were studied. The program includes subroutines for intentional dopants. For example, the observed dependency of S- doping on AsCl3 input can be explained by the formation of Ga2S. The program also supplies information regarding supersaturation, i.e. nucleation, as well as relative rates of growth and etching of the epi layer.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1980
- Accession Number
- ADA097410
Entities
People
- Richard G. Yalman
Organizations
- Antioch College