On The Influence Of Implant Isolation And Base Contact Abnormalities On The Performance And Reliability Of InGaP/GaAs HBTs

J. Levinson, M. J. Abou-Khalil and L. R. Williston
Nortel Networks
 
We studied the effect of both the separation between the emitter and the ion-implant isolation, and the surface roughness beneath the base contact on the performance and reliability of our InGaP/GaAs HBTs. We used a set of devices with four different separations (ð) between the emitter and the isolated region. We demonstrate that decreasing the separation d gives rise to periphery base currents and causes a significant drop in device lifetime. For the base contact, we show that degradation in semiconductor surface quality beneath the deposited p-ohmic metal can cause collector leakage currents, which we relate to localized spikes through the collector layer.