Abstract

Recent dramatic progress in research on InGaN based light emitters has led to the commercialisation of high brightness blue and green LEDs and announcements of room temperature lasers with lifetimes measured in thousands of hours. By altering the indium fraction the InGaN band-gap can be varied between 2.0 and 3.4eV and the tendency of the indium to segregrate leads to fluctuations of the band gap within any layer of InGaN. We show that light emission arises from the recombination of excitons strongly localised in deep potential wells associated with indium rich regions of the active region. An investigation of these localised excitons using absorption and luminescence spectroscopies applied to InGaN single quantum wells in commercial LEDs provides important insights into the mechanics of the light emission.

© 1998 IEEE