Defect analysis of degraded InGaP/GaAs HBTs

The reliability of InGaP/GaAs HBTs has been investigated widely. In order to understand the degradation mechanism, degraded HBTs were analysed in TEM and the diffusion behaviour of elements was investigated with EDXS. Dislocations were observed having their origin in the base emitter junction. Similarities with dislocations in degraded LEDs and LDs were observed. Indium diffusion out of the emitter can be detected, whereas dislocations in the emitter seem to block the out diffusion of indium. No carbon precipitations were found in the base-emitter junction area of the degraded HBTs.