Quantum Well Saturation Effect on the Reduction of Base Transit Time in Light-Emitting Transistors

Abstract

In this paper, we demonstrate the improvement of cutoff frequency of the light-emitting transistor (LET) due to quantum well (QW) band-filling phenomenon (i.e., saturation) along with the carrier capturing and escaping processes in the base region. Through microwave measurement followed by small-signal model analysis, we observe that the base transit time, τ t , of the LET is reduced evidently from 90 to 20 ps when the collector current density increases from 2.43 to 34.9 kA/cm 2 . The reduction of τ t via saturation effect can be explained by the electroluminescence spectrum and thermionic emission theory of QW.