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. (c) 2005 Elsevier Ltd. All rights reserved.