TRAP SIGNATURES OF AS PRECIPITATES AND AS-ANTISITE-RELATED DEFECTS INGAAS EPILAYERS GROWN BY MOLECULAR-BEAM EPITAXY AT LOW-TEMPERATURES

Despite many separate studies of the two dominant defects, i.e., As pr ecipitates and arsenic-antisite (As-Ga)-related traps, in GaAs epilaye rs grown by molecular beam epitaxy at low temperatures, they are seldo m examined simultaneously. In this letter, we report the detection of both defects in electron trap spectrum obtained by zero quiescent bias voltage transient current spectroscopy. The As precipitates appear as a broad continuum of states in the lower temperature region (<280 K) of the spectra whereas the As-Ga-related defect appears as a discrete peak at a higher temperature. The As-Ga-related trap has an activation energy of 0.65 eV and a capture cross section of 9.3 x 10(14) cm(2). It is found that the trap characteristic of low temperature GaAs is st rongly dependent on its growth temperature and the above mentioned def ects may not dominate in some cases. (C) 1996 American institute of Ph ysics.