R. Duer et al., TIME-RESOLVED PHOTOINDUCED INTERSUBBAND ABSORPTION - A NOVEL AND POWERFUL WAY OF STUDYING THE DYNAMICS OF QUANTUM STRUCTURE CARRIERS, Solid-state electronics, 40(1-8), 1996, pp. 555-559
A novel interband-pump intersubband-probe technique is developed in or
der to study the dynamics of photogenerated carriers and excitons in s
emiconductor superlattices by lime resolved photoinduced mid-infrared
absorption. Using variable energies for both pump and probe, the measu
red photoinduced transients yielded the photoinduced absorption spectr
a at different excitation energies, the excitation spectra at differen
t probe energies and both at varying delay times. We conclude from the
se measurements that a resonantly photogenerated excitonic population
reaches thermal distribution within a few picoseconds of the excitatio
n, much slower than photogenerated carriers with excess energy. We fin
d that it takes roughly 0.1 ns for the photogenerated population to eq
uilibrate with the lattice temperature, and that this time depends on
the excess energy by which the photogenerated population in created. A
fter thermal equilibrium with the lattice is reached, the excitonic po
pulation decays on a sub-nanosecond time scale which is linearly depen
dent on the lattice temperature.