A THEORETICAL-ANALYSIS OF THE PICOSECOND AND SUBPICOSECOND INFRARED-ABSORPTION SPECTROSCOPY OF HOT HOLES IN GERMANIUM

We present an ensemble Monte Carlo study of the thermalization and rel axation of photoexcited heavy and light holes in gallium doped p-type germanium for doping densities of 1x10(16) and 7x10(16) cm(-3). We ana lyze recently published data obtained by picosecond excite-and-probe a bsorption spectroscopy in the mid infrared, i.e., with excitation ener gies of 124 and 136 meV, and at lattice temperatures of 30, 80, and 30 0 K. The Monte Carlo simulations contain all types of intraband and in terband hole-hole and hole-optical-phonon scatterings, as well as free -carrier-induced ionizations of neutral accepters and captures of free holes by ionized accepters. Good agreement is found between the simul ated and the measured absorption changes as functions of time. Quite g enerally it turns out that the initially created nonthermal features i n the heavy- and light-hole distribution functions persist to times of typically twice the pump-pulse duration, thereby noticeably contribut ing to the initial nonlinear response. For longer times, the practical ly thermalized distributions give absorption changes which exclusively reflect the cooling dynamics of the heavy holes. (C) 1997 American In stitute of Physics.