A Novel Technique for GaN HEMT Trap States Characterisation

A newly investigated measurement approach to analysing the effects of long-term memory effects in wide band-gap semiconductor radio-frequency (RF) transistors is presented. This approach utilises a combination of hybrid-active load-pull and time-domain waveform measurement analysis, whilst adopting a novel measurement technique for initiating charge trapping-based transients in a gallium nitride (GaN) HEMT transistor. Switching actively between two load impedances with theoretically common power amplifier (PA) performance characteristics, a step function in the dynamic drain-voltage (vd) is initiated, whilst minimising gate-voltage and average drain-current variation. In isolating the step function to the drain side of the device only it is possible to extract dependencies of the RF drain-voltage on trap states in the transistor such as those that may occur when subjected to dynamic traffic in in-the-field applications. The measurement technique has shown the potential for extracting both time-constant and charge-trapping magnitude parameters for comparison with traditional pulse-IV characterisations for the purpose of modelling memory in GaN transistors.