GaN RF HEMT Reliability: Impact of Device Processing on I-V Curve Stability and Current Collapse

We present an extensive analysis of the impact of passivation and gate foot etching on the reliability and trapping behavior of gallium nitride HEMTs for RF applications. The study is based on high-temperature reverse bias (HTRB) experiments and temperature-dependent drain current transient analysis. Three wafers are analyzed, differing in gate foot etching and passivation. We demonstrate that: (i) gate foot etching and passivation significantly impact on the stability of the gate-leakage characteristics during HTRB stress; (ii) best stability is obtained through the use of low pressure chemical vapor deposition (LPCVD); (iii) current transient measurements reveal the presence of two trapping processes, E
1
and E
2
. While E
1
is found to be semiconductor-related, the time constant of trap E
2
strongly depends on the processing parameters and significantly increases in presence of optimized gate-foot etch and passivation. The results presented in this paper provide information for the optimization of advanced GaN RF devices.