Impact of intrinsic defects on excitation dependent carrier lifetime in thick 4H-SiC studied by complementing microwave photoconductivity, free-carrier absorption and time-resolved photoluminescence techniques

Abstract

Photoexcited carrier dynamics in 1014–1018 cm−3 density range was investigated by using complementary optical and microwave techniques. Bulk lifetime decrease from 4 μs to 460 ns with excitation and its increase with temperature were observed in bulk n-type 4H-SiC crystal. The latter data and modeling of excitation-dependent hole capture with subsequent electron capture provided the trap position at EV + 0.19 eV and electron (hole) lifetimes of 360 ns (100 ns), correspondingly, at high excitation conditions. Lifetime increase with temperature was observed due to the trap thermal activation and reduction of electron capture cross section. The trap origin was discussed in terms of silicon vacancy related and titanium point defects. Photoluminescence spectra in 24–300 K range revealed bound exciton luminescence and nitrogen-aluminum donor-acceptor pair band, which time-resolved and excitation dependent dynamics was analyzed.