  The principal mechanisms of Auger recombination of nonequilibrium carriers in
semiconductor heterostructures with quantum wells are investigated. It is shown
for the first time that there exist three fundamentally different Auger
recombination mechanisms of (i) thresholdless, (ii) quasi-threshold, and (iii)
threshold types. The rate of the thresholdless Auger process depends on
temperature only slightly. The rate of the quasi-threshold Auger process
depends on temperature exponentially. However, its threshold energy essentially
varies with quantum well width and is close to zero for narrow quantum wells.
It is shown that the thresholdless and the quasi-threshold Auger processes
dominate in narrow quantum wells, while the threshold and the quasi-threshold
processes prevail in wide quantum wells. The limiting case of a
three-dimensional (3D)Auger process is reached for infinitely wide quantum
wells. The critical quantum well width is found at which the quasi-threshold
and threshold Auger processes merge into a single 3D Auger process. Also
studied is phonon-assisted Auger recombination in quantum wells. It is shown
that for narrow quantum wells the act of phonon emission becomes resonant,
which in turn increases substantially the coefficient of phonon-assisted Auger
recombination. Conditions are found under which the direct Auger process
dominates over the phonon-assisted Auger recombination at various temperatures
and quantum well widths.
