Transient absorption spectra of a modulation-doped Ga0.47In0.53As/Al0.48In0.52As multiple quantum well structure measured by picosecond infrared pulses

Abstract

Intersubband and intrasubband scattering of hot electron-hole pairs is studied with picosecond infrared pulses. The carrier distribution function is derived directly from the transient absorption spectra after selective excitation of carriers to the n=1 and 2 subbands. Band filling of the n=1 conduction band results in a strong bleaching of the corresponding interband absorption and in large changes of the refractive index. An absorption change due to the population of the n=2 subbands is not detected, indicating their fast relaxation within less than 3 ps. The hot plasma cools by LO phonon emission on a time scale of several tens of picoseconds.