(Invited) AlGaN/GaN HEMT Reliability and Trap Detection Using Optical Pumping

Abstract

Changes in the drain current that correspond to charge trap energies in the band-gap of AlGaN/GaN High Electron Mobility Transistors (HEMTs) were measured when illuminated by below band-gap light. The energy of the applied wavelength of light affects the trapping and de-trapping of carriers within the band-gap, providing an indicator of trap densities. These changes were compared on HEMTs with gate lengths of 0.14 & 0.17 µm, before and after electrically stressing under on-state (VG = 0 V), off-state (VG =-5 V), and typical operating conditions (VG = -2V) indicating a change in trap density as a result of electrical stressing. Changes in trap densities were minimal after both off-state and on-state stressing but significant trap creation in the range EC¬-0.4-0.6 eV were observed in HEMTs exhibiting gradual degradation during stressing. Energy levels corresponding to these values in the literature have been suggested to correlate GaN and NGa substitutional defects, as well as GaI interstitials.