The transition from a nonthermal into a thermal distribution of electrons at low densities (< 10¹⁴ cm^-3) is traced on a picosecond time-scale by the time evolution of a band-to-acceptor transition in GaAs:Be. Two narrow, nonthermal electron distributions are detected during the first picoseconds originating from the heavy- and light-hole valence band, respectively. Measurements with circular polarization of excitation and luminescence confirm this assignment. The variation of their energetic peak-positions with excitation energy allows the experimental determination of the valence band dispersions for very small wave vectors near k equals 0, where only parabolic energy terms contribute to the dispersions. The results are consistent with the commonly used effective hole masses.

Date Published: 6 May 1994
PDF: 9 pages
Proc. SPIE 2142, Ultrafast Phenomena in Semiconductors, (6 May 1994);

Published in SPIE Proceedings Vol. 2142:
Ultrafast Phenomena in Semiconductors
David K. Ferry; Henry M. van Driel, Editor(s)