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-absorption bleaching due to the dominance of conduction-band filling over bandgap renormalization. In this letter, we show that the presence of electron traps can act to reverse this behavior so that photoexcitation results in an absorption increase in these same semiconductors. We associate this photo-induced absorption with bandgap renormalization caused by photoexcited holes that remain after the electrons have become trapped. We develop a dynamic model that predicts the wavelength dependence of photo-induced absorption and accurately describes the measured nonlinear-absorption recovery of low-temperature-grown InGaAs/InAlAs multiple quantum wells. (C) 2000 American Institute of Physics. [S0003-6951(00)03813-4].