Current Gain Enhancement of Heterojunction Bipolar Light-Emitting Transistors Using Staircase InGaAs Quantum Well

In this article, we propose heterojunction bipolar light-emitting transistors (HBLETs) with a staircase quantum well (QW) into the base region and investigate the temperature-dependent current gain of HBLET under different substrate temperatures. Our measured experimental results indicate a significant increase in current gain of approximately 73.23% at the base current,
${I} _{B}$
= 0.2 mA, and base-to-collector voltage,
${V} _{\text {CE}}$
= 2 V, as the temperature of HBLET is increased from 25 °C to 85 °C. This behavior is opposite to that of conventional heterojunction bipolar transistors (HBTs) and is primarily attributed to electrons escaping from the InGaAs QW more quickly at higher temperatures. We propose a modified charge-control model based on QW thermionic emission theory to analyze this unique temperature-dependent current gain phenomenon. The experimental results are consistent with the simulation results, and thus, this study suggests that HBLETs have the potential for design the front end of smart thermal sensors.