The 25‐Year Disruptive Path of InP/GaAsSb Double Heterojunction Bipolar Transistors

The year 2022 marks two anniversaries of broadly different significance: the 75th anniversary of the transistor invention, and the 25th since I initiated work on InP/GaAsSb double heterojunction bipolar transistors (DHBTs). Having been asked to provide a personal account of my work with transistors, it is thus fitting that I focus InP/GaAsSb DHBTs. This contribution begins by recounting a student's rather improbable interest in semiconductors due to how the topic was (and continues) to be taught to engineering students. Once interest in heterojunction transistors developed, it proved difficult for me to enter the field. After unexpected career developments led me to return to academia at a young age, I sought an original research topic: I settled on an alternative way to make InP-based DHBTs that would in principle solve many problems encountered when the traditional GaInAs alloy is used as a base layer. The article next describes the phenomenal progress of InP/GaAsSb DHBTs over the last 25 years: from a laboratory oddity in 1997 to a commercial product by 2004; from an unknown heterojunction system to THz transistors and record-breaking mixed-mode integrated circuits by 2022. The importance of human factors and of the good fortune in research is addressed. In closing, I provide remarks on the general nature of the response to disruptive technological innovation.