11.9 W Output Power at S-band from 1 mm AlGaN/GaN HEMTs

We present radio-frequency (RF) power results of GaN-based high electron mobility transistors (HEMTs) with total gate widths (Wg) up to 1 mm. The AlGaN/GaN epi-structures are MOVPE-grown on 2-inches semi-insulating (s.i.) 4H-silicon carbide substrates. The HEMTs have been fabricated using an optimized process flow comprising a low-power Ar-based plasma after ohmic contact metallization, cleaning of the AlGaN surface prior to the Schottky gate metallization using a diluted ammonia (NH4OH) solution, and passivation of the AlGaN surface using a silicon nitride layer deposited by plasma enhanced chemical vapor deposition. We will show that the best RF power performance has been achieved by HEMTs with iron-doped GaN buffer layers (GaN:Fe). Devices with a total gate width of 1 mm yielded a maximum output power of 11.9 W at S-band (2 - 4 GHz) under class AB bias conditions (VDS = 40 - 60 V, and VGS = -4.65 – - 4.0 V).