Deep Level Effects and Hot-Electron Reliability in Scaled GaN HEMTs

Carbon-related defects, introduced as doping or due to contamination during MOCVD growth, can induce dispersion effects and threshold voltage instability in GaN-based HEMTs. Back-barriers, consisting of wider bandgap materials, are adopted in order to separate channel electrons from C -doped buffers, and to reduce short-channel effects; however, trapping at GaN/back-barrier interface may still be present. Deep level effects in different 'bufferless' HEMTs technologies are discussed on the basis of case histories.