GaN HEMT With Convergent Channel for Low Intrinsic Knee Voltage

When the gated channel region of a GaN high-electron-mobility transistor (HEMT) is configured into multiple sub-channels in parallel and separated by embedded isolating patterns, the effective resistance of the access regions could be reduced, and consequently, the knee voltage (V
_K
) of the transistor could be lowered. In this work, each sub-channel is defined as a convergent funnel-like shape, with its width gradually shrunk from the source side to the drain side. Different from conventional channels with uniform width under the entire gate, the funnel-shaped-channel could converge electrons as they transport from source side to drain side, which facilitates electrons' acceleration toward saturation velocity under a smaller drain-to-source bias, leading to a reduced intrinsic V
_K
in the gated channel. Thus, more desirable I-Vcharacteristics and more balanced performance enhancement in RF linearity and power added efficiency are achieved at a low supply voltage, making the convergent-channel HEMT attractive for power amplifiers in mobile terminals.