Effects of InGaP heteropassivation on reliability of GaAsHBTs

For the self-aligned AlGaAs/GaAs HBTs with the mesa-etched emitter, the ins tability of the surface states on the extrinsic base passivated by nitride is a major cause of the severe degradation of current gain. In this paper G aAs HBTs employing InGaP ledge emitter in order to passivate the surface of the extrinsic base and to reduce the surface states exhibited the consider able improvement of the current gain reliability with the activation energy of 1.97 eV and MTTF of 4.8 x 10(8) h at 140 degrees C. However, under the strong stress conditions InGaP/GaAs HBTs also produced the considerable deg radation. The possible origins were investigated. (C) 1999 Elsevier Science Ltd. All rights reserved.