Inhomogeneous broadening of intersubband absorption bands of quantum well structures investigated by hole burning

Transient spectral holes are observed in the intersubband absorption band of a n-modulation-doped GaAs/AlGaAs quantum well structure with 5.9 nm wide wells. At 300 K, the widths of the holes amount to approximately 50% of the width of the roughly 7 meV wide intersubband absorption profile. Increasing inhomogeneous broadening and a decreasing homogeneous width are found with decreasing temperature. Well width fluctuations are discussed as dominant mechanism of the inhomogeneous broadening.