Reliability investigation of implanted microwave InGaP/GaAs HBTs

In this paper, we report the fabrication and characterisation of C-doped InGaP/GaAs microwave HBTs using a planar self-aligned technology based on O+/H+ or O+/He+ implant isolation schemes. We observed current gain variations with emitter/base geometries in the H+ implanted HBTs while no such variation was observed in the He+ implanted transistors. This latter phenomenon is characterised by a current gain increase in the smaller device and this was attributed to a decrease of the hole concentration in the base, caused by the formation of CH complexes in the C-doped GaAs base region. We therefore recommend the use of O+/He+ implant scheme for the fabrication of reliable high performance C-doped base HBTs.