Étude et réalisation de Transistors Bipolaires à Hétérojonction InP/GaAsSb/InP reportés sur substrat hôte pour application à la puissance

摘要

This thesis is focused on study, fabrication and characterization of heterojunction bipolartransistors (HBT) where GaAsSb-based active layers are transferred to a host substrate. Thegoal of this study is to provide the basis of the transistor design for power and high speedapplications.The simulation allowed to introduce, for transferred-substrate transistors, the concepts ofthermal drain taking advantage of the metal layer used by the transferred substratetechnique. It has been shown that on a substrate of poor thermal conductivity as Pyrex, thetransferred substrate technique leads to a reduction of the thermal resistance of more than30%. On a substrate of high thermal conductivity this reduction factor is as high as six.Based on these concepts, HBT fabrication technology on transferred substrate layers byanodic bonding has been developed. The fabrication of double mesa HBTs has beendemonstrated. Two difficulties have been identified in the fabrication process for highspeedHBTs.Electrical characterizations have allowed to attribute the excess of base current usuallyobserved in InP/GaAsSb heterojunctions to the antimony contents in the InP emitter layer.The absence of antimony in the emitter layer when it is grown before the base layer, as inthe case of transfered-susbtrate HBTs, cancel this parasitic effect and leads to transistorsexhibiting current gain which are independent of the collector current.On the other hand, the heating effects on the HBT electrical characteristics have beensystematically studied in order to provide guidelines in the HBT design for powerapplications. Thanks to its type II heterojunction, GaAsSb/InP HBTs present a thermoelectriccoefficient much smaller (better themal stability) than HBT using type I heterojonctions.The minority electron lifetime in GaAsSb:C is limited by Auger-type recombinations. As aresult the GaAsSb-based HBTs have a temperature constant current gain on a wide temperaturerange.All these electrical properties demonstrate that the transfered-substrate InP/GaAsSb HBTshave much better electrical and thermal stability than other HBTs. Therefore they have alarge potential for power applications.