AlGaN/GaN HEMTs on diamond substrate with over 7W/mm output power density at 10 GHz

Record RF performance of AlGaN/GaN high electron mobility transistors (HEMTs) on a diamond substrate with over 7 W/mm output power density at 10 GHz is reported. It is achieved along with the peak power-added-efficiency over 46% and power gain over 11 dB for 2 × 100 μm gate-width HEMTs at 40 V drain bias. Device wafers are prepared by first removing the host Si (111) substrate and nitride transition layers beneath the channel, depositing a 50 nm dielectric onto the exposed GaN buffer, and finally growing 100 μm of a chemical vapour deposition diamond onto the dielectric adhering to the epitaxial AlGaN/GaN. This approach enables the active GaN channel to be brought within 1 μm of the diamond substrate. Test HEMTs are fabricated using a dielectrically defined 0.25 μm gate length process.