High‐power‐density InAlGaN/GaN HEMT using InGaN back barrier for W‐band amplifiers

This paper investigated the back‐barrier (BB) effect for gallium nitride (GaN)‐based high‐electron‐mobility transistors with an Fe‐doped buffer and Fe‐buffer + Indium gallium nitride (InGaN)‐BB structure. The authors found that the Fe‐doped buffer + InGaN‐BB structure was effective in reducing the off‐state leakage current compared to the Fe‐doped buffer. Secondary‐ion‐mass spectrometry measurements revealed that the segregated Fe existed with peaks at ∼2 × 1017 cm−3 around the InGaN‐BB layer. The authors believe that the negative charges which are generated by Fe effectively increased the BB effect as they exist just underneath the 2‐dimensional‐electron‐gas channel and successfully achieved a high output power operation of 4.6 W/mm at 94 GHz. The high output power density of 4.6 W/mm at 94 GHz was achieved for GaN‐HEMT using Fe‐buffer + InGaN BB structure.