Subcircuit Modeling of Dual Channel MOS-HEMTs Using Standard ASM-HEMT

In this article, we present a physics-based subcircuit model for a dual-channel MOS-High Electron Mobility Transistor (DC-MOS-HEMT), developed within the industry standard advanced SPICE model (ASM)-HEMT framework. In contrast to a typical MOS-HEMT, a DC-MOS-HEMT features two channels; an upper channel defined between the Al2O3/GaN layer and a lower channel formed between the AlN/GaN layers. A subcircuit approach has been presented using two coupled transistors connected in parallel to mimic the dual channel behavior. To incorporate the effect of channel separation on the threshold voltage of the device, a separate threshold voltage model has been developed for the upper and lower channels. The screening effect on the lower channel due to the charge carriers in the upper channel is modeled using an effective gate voltage for the lower channel. The impact of the intermediate GaN layer thickness on the charge density profile of the upper and lower channels is also investigated. The proposed model accurately captures the two humps observed in the transfer ${I}-{V}$ and capacitance–voltage ( ${C}-{V}$ ) characteristics, including two peaks observed in the transconductance. The dual channel behavior has been modeled and validated with experimental data, including continuous wave (CW) and pulsed measurements.