AlGaN/GaN Microwave Switch With Hybrid Slow and Fast Gate Design

We present a novel approach to reduce the off-state capacitance of microwave transistor switches. The new design includes a “slow gate” layer, which allows for complete depletion of the channel in the source-drain region, thus reducing the gate-channel capacitance. Due to very high impedance at high frequencies, the “slow gate” shunting effect and its own capacitance contributions are negligibly small. This novel approach is validated by demonstrating an AlGaN/GaN single-pole double-throw switch with the “slow gate” layer formed by InGaN film. The new gate design decreases the insertion loss of the fabricated switch by approximately 0.5 dB and increases the isolation by approximately 5 dB.