Hole-induced transient bandgap renormalization: A mechanism for photo-induced absorption in defect-engineered semiconductors

In semiconductors, photoexcitation often results in a transient band edge-a bsorption bleaching due to the dominance of conduction-band filling over ba ndgap renormalization. In this letter, we show that the presence of electro n traps can act to reverse this behavior so that photoexcitation results in an absorption increase in these same semiconductors. We associate this pho to-induced absorption with bandgap renormalization caused by photoexcited h oles that remain after the electrons have become trapped. We develop a dyna mic model that predicts the wavelength dependence of photo-induced absorpti on and accurately describes the measured nonlinear-absorption recovery of l ow-temperature-grown InGaAs/InAlAs multiple quantum wells. (C) 2000 America n Institute of Physics. [S0003-6951(00)03813-4].