Excitonic and electron-hole contributions to the spontaneous recombination rate of injected charge carriers in GaAs-GaAlAs multiple quantum well lasers at room temperature

The spontaneous recombination rate at room temperature of GaAs-GaAlAs multiple quantum well lasers is investigated at carrier densities of 2×1017–1.7×1018 cm−3 using the small-signal electroluminescence technique. A monomolecular, partly excitonic, and a bimolecular term contribute to the recombination rate R(n)=An+Bn2, where A and B are 2.08×108 s−1 and 1.5×10−10 cm3 s−1, respectively, for a well width Lz =7.5 mm. The radiative and nonradiative contributions to the linear recombination term, A=1/τr+1/τnr, are determined as τr =8 ns and τnr =12 ns from the dependence of the spontaneously emitted light power on the injection current density. In addition the carrier density dependence of the internal quantum efficiency is reported and ηi is found to be close to unity. The results demonstrate that even at fairly high excitation levels, excitonic enhancement of radiative recombination in high quality multiple quantum well structures is an important factor.