DEEP-LEVEL PLANAR DOPING OF TITANIUM IN GAAS

Titanium is incorporated in GaAs by planar doping during growth interr uption of molecular beam epitaxy. Deep-level defects are studied by me asuring the capacitance and ac conductance in dependence on bias, freq uency, and temperature. We report on the first investigation of the dy namic behavior of deep electronic states at interfaces intentionally d oped with electrically active defects. Admittance versus bias spectros copy at sufficiently low frequencies is proposed as a new method to de tect deep levels exclusively at interfaces in homo- or heterojunctions . For the planar-doped titanium sheet, an intrinsic point defect level at 0.35 eV is identified in addition to the Ti2+/Ti3+ acceptor level at 0.24 eV. The incorporation of Ti is accompanied by the formation of native defects. The majority of Ti atoms is found to be electrically inactive.