Planar self-aligned microwave InGaP/GaAs HBTs using He+/O+ implant isolation

Abstract

The fabrication results of InGaP/GaAs HBTs using a planar technology are presented. The device isolation was achieved by ion implantation using oxygen and hydrogen ions. However, this combination of ions produced a new problem related to carbon acceptor passivation inside the base layer of the HBT. To avoid this situation, hydrogen was replaced with heavier and thus less diffusive helium ions. Measured characteristics of the He+/O+ implanted HBTs show no variation of current gain with device geometry and suggest that the problem related to passivation of carbon accepters inside the base has completely been resolved. The fabricated InGaP/GaAs microwave HBTs show an almost uniform cut-off frequency, fT, of about 35 GHz for an emitter area of 8×10 μm2