Relaxation cavityless optical bistability is studied when a semiconductor i
s exposed to light quanta with an energy exceeding the transition energy an
d the free-electron relaxation time depends on temperature. The numerical a
nalysis of dynamic equations for temperature and free-electron density demo
nstrates that 11 regimes of light-semiconductor interaction are possible. T
he regimes are classified in terms of the features of temperature-intensity
characteristic curves, namely, by the number and arrangement of instabilit
y and quasi-stability segments and by the presence or absence of bistabilit
y. It is found that both the upper and the lower branch of a bistable chara
cteristic curve may be unstable, which results in spontaneous switchings be
tween the respective states. Similarly, if the upper state is unstable and
the lower state is stable, a small perturbation of the parameters (free-ele
ctron temperature and density) near the former causes the transition to the
oscillatory regime. If the upper state is unstable and a small perturbatio
n of the lower (stable) state excites a damped oscillation, spontaneous swi
tchings result if the fluctuating temperature exceeds some critical value f
or the lower state. (C) 2000 MAIK "Nauka/Interperiodica".