Current Gain Enhancement at High-Temperature Operation of Triple-Quantum-Well Heterojunction Bipolar Light-Emitting Transistor for Smart Thermal Sensor Application

In this article, we present an investigation into the amplification characteristics of triple-quantum-well heterojunction bipolar light-emitting transistors (TQW-HBLETs or TQW-HBTs or TQW-LETs) at varying ambient temperatures. Our analysis involves a modified charge-control model that integrates the idea of thermionic emission of electrons from the TQWs, which are strategically positioned within the base region of HBTs. Both experimental measurements and simulations demonstrate that the minority carrier within the TQWs acquires greater energy at higher operating temperatures, facilitating its rapid escape from the TQWs due to a reduced escape time. Interestingly, this phenomenon leads to a distinct augmentation in the current gain, contrary to the conventional behavior observed in HBTs. Specifically, we observed a remarkable increase in current gain of approximately 200%, when the operating temperature of TQW-HBTs is elevated from 25 °C to 85 °C. Notably, the experimental findings align consistently with the outcomes obtained through simulations. Consequently, our study presents a compelling case for the application of light-emitting transistors (LETs) in the design of cutting-edge smart thermal sensors, illustrating their promising potential in the front end of such systems.