INFLUENCE OF HYDROGEN RADICALS ON THE REDUCTION OF CARBON INCORPORATION INTO CHEMICAL BEAM EPITAXIAL GAAS

In order to investigate the influence of hydrogen radicals (H.) on carbon incorporation into chemical-beam epitaxial GaAs, H. generated by flowing H-2 through a hot tungsten filament was intentionally introduced into a trimethylgallium (TMGa)-AsH3 (cracked at 850 degrees C) and a TMGa (or metal Ga)-trisdimethylaminoarsine (TDMAAs) system. In the case of the TMGa-AsH3-H. system, the residual carbon concentrations, measured by secondary ion mass spectrometry, in epitaxial layers grown at 490 degrees C rapidly decreased along with an increase in the H-2 flow rate in a low-flow region, and saturated at around 1 x 10(18) cm(-3) in a higher flow region. On the other hand, carbon incorporation (6 x 10(17) Cm-3 at 490 degrees C) in TMGa-TDMAAs was less than that in TMGa-AsH3. Since no residual carbon over the detection limit ((1-2) x 10(17) cm(-3)) was detected in metal Ga-TDMAAs, the carbon in TMGa-TDMAAs was clarified as having been derived from TMGa. However, the introduction of H. did not reduce the carbon incorporation in TMGa-TDMAAs. Influence of injected H. on the carbon reduction is discussed in relation to the adsorption of uncracked H-2 and surface species derived from TDMAAs on a growing surface.