Temperature-Dependent RF Characterization of GaN-Based K-Band to V-Band IMPATT Diodes

High-gain GaN impact-ionization avalanche transit-time (IMPATT) diodes have been fabricated and experimentally characterized. The devices feature a “Hi-Lo” doping profile design; temperature-dependent reverse $I$ – $V$ measurement verified impact ionization avalanche as the dominant breakdown mechanism. IMPATT operation was confirmed, with reflection gain observed between 19.3 and 50.1 GHz using pulsed bias conditions of −175 V and current density of 7.6 kA/cm 2 . Apeak reflection gain of 1.97 dB was observed around 30.8 GHz. On-wafer S-parameter measurements revealed a large negative differential resistance (NDR) of $- 992~\Omega $ , comparable to state-of-the-art Si IMPATT diodes. The RF output power density is projected to be 40.3 kW/cm 2 at 35 GHz. The short-pulse on-wafer S-parameter-based measurement technique used here facilitates direct extraction of device impedance, providing insights into the optimal impedance matching of the peripheral resonant circuit and the appropriate operating frequency. Temperature-dependent characterization shows that the avalanche frequency has a much stronger dependence on current density rather than bias voltage. Therefore, biasing with a current source is preferred compared to a voltage source for stable operation in applications. The maximum operating frequency is found to increase at higher temperatures, possibly due to a decrease in the series resistance associated with the anode’s p-contact resistance. These devices are promising for high-power, high-efficiency K-band to V-band signal generation across a broad temperature range.