Drain E-Field Manipulation in AlGaN/GaN HEMTs by Schottky Extension Technology

The proposed hybrid Schottky-ohmic drain structure is analyzed in detail for AlGaN/GaN power high-electron mobility transistors on the Si substrate. Without any additional photomasks and process steps, the hybrid drain design can alter the electric field distribution to improve the breakdown voltage V_BK. In addition, it provides an additional current path to achieve zero onset voltage and reduce the ON-resistance. It was found that the Schottky extension L_ext is critical to V_BK, R_ON, and also the current collapse phenomena of the transistors. The extended Schottky electrodes for optimized transistor characteristics are investigated, and the physics behind are discussed. With an L_ext ~ 2-3 μm, V_BK can be improved up to 60% with an R_ON degradation below 3%.