  Electron and phonon transient temperatures are analyzed in the case of
nondegenerate semiconductors. An analytical solution is obtained for
rectangular laser pulse absorption. It is shown that thermal diffusion is the
main energy relaxation mechanism in the phonon subsystem. The mechanism depends
on the correlation between the sample length and the electron cooling length in
an electron subsystem. Energy relaxation occurs by means of the electron
thermal diffusion in thin samples (), and by means of the electron-phonon
energy interaction in thick samples (). Characteristic relaxation times are
obtained for all the cases, and analysis of these times is made. Electron and
phonon temperature distributions in short and long samples are qualitatively
and quantitatively analyzed for different correlations between the laser pulse
duration and characteristic times.
