Temperature and Bias Dependent Trap Capture Cross Section in AlGaN/GaN HEMT on 6-in Silicon With Carbon-Doped Buffer

We report on the estimation of trap capture cross section in AlGaN/GaN HEMTs as a function of bias and temperature. Conductance dispersion technique was employed to study the AlGaN/GaN interface of the devices with a carbon-doped GaN buffer grown on 6-in silicon. While a negligible shift in the threshold voltage (VTH) was observed in temperature-dependent IDS-VGS sweeps, we observed a spread in the capacitance-voltage (C-V) measurements, indicating a contribution of interface traps. When biased near depletion, G/ω versus frequency plot for AlGaN/GaN interface exhibits two peaks which correspond to a pair of trap density (Dit) and trap time constant (Tit) values. This was explained using a circuit model in conjunction with energy band diagram. The Dit and Tit values for one peak were in the range from ~ 0.3-7 × 10¹²/eV · cm² and 0.6-10 μs while for the other peak, Dit-Tit were in the range of ~0.1-35 × 10¹²/eV · cm² and ~0.06-0.3 μs at 25 °C. From the Tit values, electron capture cross section (σ) for both the traps was extracted and was found to be decreasing with increasing temperature in the range of 1.1 × 10^-20-1 × 10-19 cm² and 4.5 × 10^-20-1 × 10-17 cm² for slow traps and fast traps, respectively. A multiphonon emission effect was invoked to explain the temperature dependence of capture cross section.