Control of radiative base recombination in the quantum cascade light-emitting transistor using quantum state overlap

The concept of the quantum cascade light-emitting transistor (QCLET) is proposed by incorporating periodic stages of quantum wells and barriers in the completely depleted base–collector junction of a heterojunction bipolar transistor. The radiative band-to-band base recombination in the QCLET is shown to be controllable using the base–collector voltage bias for a given emitter–base biasing condition. A self-consistent Schrödinger–Poisson Equation model is built to validate the idea of the QCLET. A GaAs-based QCLET is designed and fabricated. Control of radiative band-to-band base recombination is observed and characterized. By changing the voltage across the quantum cascade region in the QCLET, the alignment of quantum states in the cascade region creates a tunable barrier for electrons that allows or suppresses emitter-injected electron flow from the p-type base through the quantum cascade region into the collector. The field-dependent electron barrier in the base–collector junction manipulates the effective minority carrier lifetime in the base and controls the radiative base recombination process. Under different quantum cascade region biasing conditions, the radiative base recombination is measured and analyzed.