DIMETHYLARSINE - PYROLYSIS MECHANISMS AND USE FOR OMVPE GROWTH

The pyrolysis mechanisms of dimethylarsine (DMAsH) have been studied mass spectrometrically in an atmospheric pressure flow tube reactor. In either the D2 or He ambient, DMAsH will be converted to trimethylarsine (TMAs) at temperatures of 400-500° via a homogeneous CH3 radical chain reaction. Supplemental CH3 radicals, produced from azomethane ((CH3)2N2) pyrolysis, have resulted in a significant increase in the pyrolysis rate for DMAsH. As temperature is increased beyond 500°, the product TMAs will decompose due to hydrogenolysis in D2 and homolysis in He. At a GaAs surface, DMAsH pyrolyzes heterogeneously. The pyrolysis rate is further accelerated by the addition of trimethylgallium (TMGa). DMAsH has also been combined with TMGa to grow GaAs layers. The as-grown epilayers, at 1 atm and substrate temperatures of 570-720°, are all p-type with the net hole concentration dependent on the carrier gas. The use of N2 leads to a higher concentration as compared to that in H2. Photoluminescence spectra have indicated the acceptor to be carbon. A mechanism is developed to interpret these results based on the pyrolysis reactions determined from the kinetic studies. © 1990 The Mineral,Metal & Materials Society,Inc.