Electron and hole traps in GaN p-i-n photodetectors grown by reactive molecular beam epitaxy

GaN p-i-n photodetectors grown on sapphire by reactive molecular beam epitaxy have been characterized by measurements of room-temperature current-voltage (I-V), temperature-dependent capacitance (C-V-T), and deep level transient spectroscopy (DLTS) under both majority and minority carrier injection. Due to what we believe to be threading dislocations, the reverse I-V curves of p-i-n photodetectors show typical electric-field enhanced soft breakdown characteristics. A carrier freeze-out due to the de-ionization of Mg-related deep acceptors has been found by C-V-T measurements. Three electron traps, B (0.61 eV), D (0.23 eV), and E1 (0.25 eV) and one hole trap, H3 (0.79 eV) have been revealed by DLTS measurements. The photodetectors with lower leakage currents usually show higher responsivity and lower trap densities of D and E1.