Observing Electroluminescence from Yellow Luminescence-Like Defects in GaN High Electron Mobility Transistors

Abstract

A yellow band electroluminescence (EL) characteristic, which might be attributed to the same origin as the yellow luminescence (YL) defects, was observed in GaN high electron mobility transistors (HEMTs) at room temperature. The YL-like defect origin has been tentatively confirmed by comparing EL and photoluminescence (PL) results. To further explore the properties of YL-like EL centers, EL dependence on the drain-to-source and gate-to-source voltage were investigated. The direct comparison between the EL and temperature distribution images from the same GaN HEMT suggests that two distinct EL emission mechanisms exist at the off-state breakdown. The other type of EL emission at off-state is attributed to carrier intravalley transition due to hot carrier generation by impact ionization at localized breakdown sites. This type of hot carrier induced light emission was observed at on-state and off-state operations. The YL-like emission was shown to have a stronger electric field than the hot carrier induced emission.