Analysis of charge separation dynamics in a semiconductor junction

Abstract

Charge separation has been experimentally observed in a number of junction devices over the last decade, but there has been little theoretical analysis of the phenomena that describes the detailed dynamics of the effect. In this work, we use computer simulations to assess the ability of time-resolved photoluminescence, resonant-coupled photoconductive decay, and other experimental techniques to characterize free-carrier recombination and charge separation after an ultrafast laser pulse excites carriers in a homojunction or a heterojunction. The results indicate the experimental conditions where charge separation is likely to dominate these measurements and several experimental signatures that can be used to distinguish charge separation from free-carrier recombination. Time-resolved photoluminescence and resonant-coupled photoconductive decay measurements on Si, GaAs/ GaxIn1˛xP, and other junctions confirm and illustrate the results.