Negative transconductance effect in p-GaN gate AlGaN/GaN HEMTs by traps in unintentionally doped GaN buffer layer*

Abstract

We investigate the negative transconductance effect in p-GaN gate AlGaN/GaN high-electron-mobility transistor (HEMT) associated with traps in the unintentionally doped GaN buffer layer. We find that a negative transconductance effect occurs with increasing the trap concentration and capture cross section when calculating transfer characteristics. The electron tunneling through AlGaN barrier and the reduced electric field discrepancy between drain side and gate side induced by traps are reasonably explained by analyzing the band diagrams, output characteristics, and the electric field strength of the channel of the devices under different trap concentrations and capture cross sections.