Theoretical and experimental identification of Si DX centers and deep levels in n-type Al0.85Ga0.15N

Deep-level transient spectroscopy (DLTS), steady-state photocapacitance (SSPC), and deep-level optical spectroscopy (DLOS) were employed to investigate trap states in metal-organic chemical vapor deposition-grown Al0.85Ga0.15N with differing silicon concentrations. DLTS measurements revealed two electron traps with emission energies of 0.42 and 0.55 eV in both samples. The DLTS signals exhibited clear temperature dependence, which was consistent with capture barriers of 0.23 and 0.33 eV for the 0.42 and 0.55 eV traps, respectively. The concentrations of these traps were found to be significantly higher in the heavily doped sample, suggesting that both traps were Si related. These experimental findings are in good agreement with theoretical predictions for both vertical and horizontal silicon DX centers, suggesting that the traps observed in DLTS are most likely associated with Si DX centers. Additionally, DLOS measurements identified three additional traps with energy levels at EC − 1.66, EC − 2.42, and EC − 5.29 eV. However, the SSPC-measured trap concentrations were more than an order of magnitude lower than the 0.42 eV level, indicating the importance of reducing the likely Si DX centers.