PICOSECOND DYNAMICS OF QUANTUM STRUCTURE CARRIERS MEASURED BY TIME-RESOLVED PHOTOINDUCED INTERSUBBAND ABSORPTION

A novel interband-pump intersubband-probe technique is developed in or der to study the dynamics of photogenerated carriers and excitons in G aAs/AlGaAs superlattices by time resolved photoinduced absorption. The photogenerated population reaches a thermal distribution a few picose conds after the excitation. The time dependence of the intersubband ab sorption strength and its time resolved excitation spectra yield a mea sure for the time it takes for that population to cool first to the la ttice temperature and then to radiatively decay. The first time is rou ghly 70-100 ps depending on the excess energy with which the photogene rated carriers are created. The second is on a sub-nanosecond scale an d depends linearly on the lattice temperature.