Identifying the spatial position and properties of traps in GaN HEMTs using current transient spectroscopy

• A new method for the extraction of the time constants of traps from the current transients is proposed.
• The spatial positions of two traps were identified in the AlGaN barrier layer and the GaN layer, respectively.
• The trap in the AlGaN barrier layer requires sufficient electric field to activate the trapping process
• High drain voltage accelerates the trapping processes both in the AlGaN barrier layer and the GaN layer.

Time constant spectra are extracted from current transients based on the Bayesian deconvolution and used to characterize traps in GaN high-electron mobility transistors. Two kinds of traps with different time constants in an actual device were identified in the AlGaN barrier layer and the GaN layer, respectively. In particular, the trapping process in the AlGaN barrier layer was identified at the region near the drain side under gate contact. Trapping mechanisms of both two traps are discussed. Additionally, we observe that the trap in the AlGaN barrier layer requires sufficient electric field to activate the trapping process and a high drain voltage (Vds) accelerates the trapping processes both in the AlGaN barrier layer and the GaN layer. In addition, detrapping experiments with different filling conditions were performed to confirm their spatial positions. The influence of self-heating is excluded during the experiment by keeping the power density at a very low level, and the trapping effect is the sole factor accounting for the current transients.