A number of optoelectronic threshold effects arising under intensive stimulated radiative recombination of hot dense electron-hole plasma (EHP) in a thin (~1um) epitaxial layer of GaAs has been revealed. These effects' build-up and decay time intervals are of ~10 ps or less at room temperature (which makes it possible to modulate the optical and electrical properties of semiconductor heterostructures and devices with a frequency of ~ 100 GHz). These effects are observed when the stimulated recombination emission appears in picoseconds. The emission intensity can be as high as ~108 W/cm2 and the EHP concentration can change several times by magnitude. The revealed class of optoelectronic effects has its origin in strong mutual influence between the stimulated emission and dynamical processes in dense EHP. The acquired knowledge of somewhat uncommon mechanism of changes of EHP concentration and temperature, of intensity and spectrum of stimulated emission, of the gain, transparency, band-gap width, etc. can be used for successful construction of semiconductor high-speed powerful optoelectronic devices (such as semiconductor lasers and superluminescence diodes, semiconductor light-wave converters, modulators of the optical transparency and photoconductivity7
