Negative capacitance in GaN/AlGaN heterojunction dual-band detectors

A study of trap states in n+-GaN∕AlGaN heterostructures using electrical, thermal, and optical analyses is reported. Capacitance-voltage-frequency measurements showed negative capacitance and dispersion, indicating interface trap states. Infrared spectra identified three impurity related absorption centers attributed to shallow Si-donor (pinned to the AlGaN barrier), N-vacancy/C-donor, and deep Si-donor (pinned to the GaN emitter) impurities with corresponding activation energies of 30.8±0.2, 125±1, and 140±2meV, respectively. The shallow Si-donor impurity had a relaxation time of 155±9μs, while the C-donor/N-vacancy and deep Si-donor impurities appear to behave as a single trap state with a relaxation time of 1.77±0.05μs. Multiple analysis techniques allowed the determination of the activation energies of these impurity related centers and the study of the effects of trap states on the electrical behavior of the detector.