The Mechanisms of Electron Transport in Highly Doped Al_XGa_1-XN:Si (X > 0.65)

Highly conductive contact layers are an integral aspect of modern electronics. Al_XGa_1-XN, due to its ultrawide bandgap (5-6 eV) and high breakdown voltage (10MV/cm²), is a promising material for the production of UV LEDs and high-power electronics. However, previous research shows an increase in activation energy for conduction with increasing aluminum mole fraction, making highly conducting contact layers a challenge. Therefore, this research seeks to better understand electron transport in heavily silicon doped, high aluminum content Al_XGa_1-XN (X > 0.65), specifically by monitoring the neutral donor concentration with 10 GHz electron paramagnetic resonance (EPR). Samples were doped on the order of 10¹⁸ – 10²⁰ [cm^-3] and were measured from room temperature to 4K. The temperature dependence of the neutral donor EPR spectra linewidth and intensity were measured, and statistical models were used to understand the mechanism of transport in these high Al mole fraction AlGaN samples. The results of this research indicate the presence of impurity band conduction and electron hopping as well as the presence of compensating centers.