TE DOPING WITH DIMETHYLDITELLURIDE DURING ORGANOMETALLIC VAPOR-PHASE EPITAXY OF GAAS

Dimethylditelluride has been used as a dopant source for GaAs epilayers grown by atmospheric pressure organometallic vapor phase epitaxy. The highest electron concentration obtained, n = 2.7 X 10(19) cm(-3), appears to be the highest electron concentration ever obtained in VPE GaAs consistent with mirror-like morphology. The electron and Te concentrations are virtually the same, as determined by SIMS, CV, and Hall effect. Electron concentrations are routinely obtained above 1 X 10(19) cm(-3) over a range of growth temperatures and low V/III ratios of 5-10. The relationship between electron concentration and dopant mole fraction, group V mole fraction, growth temperature and growth rate have been studied. A model of Fermi-level pinning at the surface is consistent with the observed Te incorporation. Excellent morphology combined with high electron concentration requires the use of high growth rates, r(g) greater than or equal to 6 mu m/h. We have extended the measured mobility vs electron concentration curve to n = 3.3 X 10(19) cm(-3). Our results also indicate that the highest Te concentrations obtained are in excess of the solubility limit.