New thermometry and trap relaxation characterization techniques for AlGaN/GaN HEMTs using pulsed-RF excitations

This paper presents new microwave characterization techniques to (1) estimate the internal device operating temperature and (2) extract the trap relaxation time-constants in AlGaN/GaN HEMTs. The operating temperature of the device under CW large-signal RF operation is obtained using isothermal pulsed-IV/RF measurements with increasing substrate temperatures. The trap capture and emission times are measured by monitoring the time relaxation of the transient bias drain current in pulsed-IV when a train of large-signal pulsed-RF excitations is applied and removed respectively. Illumination is further verified to accelerate the emission process confirming the trapping activity and identifying trap energy levels. In addition, it is verified that higher RF load impedances for the same biasing, strongly increase the trapping as the instantaneous drain voltage reaches higher peak values.