Thermal properties and thermal instabilities of InP-based heterojunction bipolar transistors

We investigate the physical parameters which are critical to the understanding of the thermal phenomena in InP-based heterojunction bipolar transistors. These parameters include thermal resistance, thermal-electric feedback coefficient, current gain, and base-collector leakage current. We examine the thermal instability behavior in multi-finger HBTs, and observe for the first time the collapse of current gain in InP-based HBTs. Based on both measurement and modeling results, we establish the reasons why the collapse is rarely observed in InP HBT's, in a sharp contrast to AlGaAs/GaAs HBT's. We compare the similarities and differences on how InP-based HBT, GaAs-based HBT, and Si-based bipolar transistors react once the thermal instability condition is met. Finally, we describe the issues involved in the design of InP HBTs.