Integration of top-side low-temperature diamond on AlGaN/GaN RF HEMT for device-level cooling

Self-heating and related degradation in performance and reliability are serious concerns in realizing higher output power density in microwave power amplifiers. We demonstrated the integration of polycrystalline diamond on a fully fabricated metal-polar Schottky-gated AlGaN/GaN microwave transistor for the device-level cooling solution. The thermal budget of the diamond integration process is carefully optimized so as not to degrade the electrical performance of the device. Gate resistance thermometry measurement performed on a 1 × 200 μm2 device showed an average 111 °C lower channel temperature from 488 °C for the devices with diamond at 24 W/mm power dissipation than those without diamond. The gate leakage current of the device increased only by 4.8 times with the optimized diamond growth process. An extrinsic Ft/Fmax of 23/33 GHz was measured on devices with diamond compared to 23/36 GHz on devices without diamond. Diamond integration and gate leakage current modeling were also discussed on a 10-finger HEMT.