Blueshift of effective band gap in n-i-p-i doping superlattices as a function of optical excitation intensity

Abstract

It is a well-established fact that the luminescence peak arising from spatially indirect transitions (effective band gap Eeff g) of a n-i-p-i structure shifts to a higher energy when the intensity of the excitation is increased. In this article, the quantitative dependence of the effective band gap on the excitation light intensity IW is formulated and verified experimentally. Using AlGaAs based n-i-p-i samples, the plot of ln(IW) versus Eeff g gives a slope of value 4 × 10-21 eV-1 which agrees well with the theoretical value of 5.2× 10-21 eV-1. It is found that this blueshift is typically 50 meV for a doubling in the magnitude of the optical excitation intensity from 50 to 100 mW cm-2. Further, it is found that the carrier lifetime decreases exponentially with an increase in the excitation intensity from zero to 500 mW cm-2 by four orders of magnitude which also agrees well with our theoretical model. © 1998 American Institute of Physics.