Interaction of Defects with Quantum Well States: Electrostatic-Dependent Response Time for Traps in AlGaN/GaN HEMTs

摘要

Recovery transients in high-voltage AlGaN/GaN HEMTs following both blocking voltage and ON-state stress show strong dependence on stress time. The defect time constant spectra exhibit a temperature-dependant component (TG1, E_a = 0.6 eV) and a temperature-independent component (TG2). With increased stress time and larger current collapse, the time constants for TG2 become progressively longer. The stress-time-dependent behavior of TG2 is shown to be consistent with the capture of trapped carriers in the AlGaN barrier directly by quantum well states, originating from the same defect giving rise to the 0.6 eV behavior. By modulating this alternate recombination pathway, the electric field normal to the AlGaN/GaN interface is shown to have a strong effect on reducing the response time of the trap to several orders of magnitude below its bulk response time. This demonstrates that barrier design may be utilized to tune the recovery characteristics of the HEMT.