Growth and characterization of NpN heterojunction bipolar transistors with In0.03Ga0.97N and In0.05Ga0.95N bases

The material and device characteristics of InGaN/GaN heterojunction bipolar transistors (HBTs) grown by metalorganic chemical vapor deposition are examined. Two structures with different p-InxGa1−xN base region compositions, xIn=0.03 and 0.05, are presented in a comparative study. The higher indium content base is expected to provide improvements in device performance via its higher p-type doping efficiency and lower bulk resistivity. However, the DC gain for both devices is the same at ∼37. The tradeoffs involved with using higher indium composition in the base for NpN HBTs are investigated by atomic force microscopy, Hall-effect measurement, and device characterization.