Simulation on the effect of non-uniform strain from the passivation layer on AlGaN/GaN HEMT

High electron mobility transistors (HEMTs) based on the III-nitride material system have attracted interest for high-frequency electronic components operating at high-power levels. Nitride based HEMTs can achieve power, bandwidth and efficiency levels that exceed the performance of Si, GaAs or SiC based devices. At present, a major limitation of nitride HEMTs is their failure to achieve reliability on par with Si-LDMOS or GaAs pHEMT devices. The development of SiNx passivation layers have largely mitigated the gate lag effect, however, this passivation layer introduces an additional strain that forms a non-uniform polarization induced charge. Furthermore, this excess strain can locally relax the film eliminating the piezoelectric induced charge in addition to forming defects that act as electron traps.