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 smallsignal 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.Index Terms-Carrier capture and escape time, light-emitting transistor (LET), quantum well (QW) saturation.