No abstract

The carrier recombination rate in GaAs-AlGaAs single quantum well layers is investigated using a small-signal technique for carrier densities from 1017 to 1019/cm3. For carrier densities up to mid 1018/cm3, the inverse of the differential carrier lifetime, 1/τd, increases linearly with the carrier density. The differential rate, however, saturates at higher carrier densities and remains nearly constant for carrier densities higher than 1019/cm3. The deviation from the bulk recombination behavior is due to a portion of the injected carriers populating the semicontinuum states where the rate for the radiative transition is much smaller. The experimental data indicate that the runaway increase of threshold current with decreasing cavity length commonly observed in the short-cavity lasers is mainly due to the loss of carrier confinement at high carrier densities rather than due to fast carrier-depleting processes, such as Auger recombination.

A new scheme of energy storage in single-quantum-well semiconductor lasers is analyzed. This scheme involves the storage of the majority of injected carriers in the continuum states of the surrounding bulk material, in which the carrier density is diluted and the higher-order carrier-density-dependent recombination processes are much smaller. This allows the inversion level to build up to a much higher level during the pumping stage of Q switching. The possibility of using indirect-band-gap semiconductors for carrier storage is also proposed.