Base transport factor and frequency response of transistor lasers

Abstract

We report on a charge control analysis that relates the characteristic time constants of a three-port laser made of a quantum-well (QW) heterojunction bipolar transistor (HBT) to the electronic gain of the device. For this purpose, we take into account the linear variation of the base transport factor α with the HBT base current. Our approach enables us to obtain QW capture time, base recombination lifetime, and base transit time in terms of the experimental values of base current and of the transistor laser (TL) design parameters such as base width, QW width, and QW location. Whereas the base recombination lifetime is calculated to be a fraction of a nanosecond, the QW capture time is found to be of the order of a picosecond or less. The time constants obtained from our model are used to successfully reproduce the TL experimental optical frequency response.