Role of rate window, transient time, and reverse bias field on the deep levels of LT-GaAs by field effect transient spectroscopy

Abstract

We have investigated the effect of rate window, transient time, and reverse bias field on the deep levels in molecular beam epitaxy (MBE) grown, Si-doped, low temperature (LT) GaAs by field effect deep level transient spectroscopy (FEDLTS). As far as we know, this is the first successful paper on LT-GaAs investigated by FEDLTS. The applied rate window (R=t2/t1) ranged from 5 to 8 with interval 1, transient time from 5 to 50 s, and reverse bias field from −0.5 to −4×105 V/cm. The capacitance transients (CT) were recorded from 70 to 380 K at temperature intervals of 0.5, 1, or 2 K and analyzed by modulating function waveform analysis. The CT were relatively strong marked by very short growth time (∼5 s). At the measurement transient time greater than 5 s, the CT began to deteriorate showing no further resolution. On the other hand, the FEDLTS spectra were quite dense due to a large number of overlapping deep levels which were found to be very sensitive to the selection of rate window, measurement transient time, and reverse bias electric field. LT-GaAs was found to posses as many as nine electron trap levels in contrast to five deep trap levels observed in MBE-grown, Si-doped, high temperature GaAs studied earlier.