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 (VK) 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 VKin 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.