Optical gain and loss processes in GaInAs/InP MQW laser structures

The experimental determination of unsaturated optical gain in GaInAs/InP multiple-quantum-well heterostructures is reported. A pronounced step-like line shape of the optical gain spectra is observed, directly reflecting the two-dimensional (2-D) nature of the carrier system. An excellent description of all experimental data is obtained by applying a microscopic theory for the radiative recombination processes. From detailed line shape analyses, two-dimensional carrier densities up to 11×10² cm^-2 and internal absorption coefficients up to 1000 cm^-1 at room temperature are derived. A steep decrease of the differential quantum efficiency above 240 K reveals the importance of intervalence band absorption in quantum-well (QW) lasers. Auger processes are quantitatively investigated in 2-D lasers. The threshold behavior of QW lasers is discussed using the experimentally determined absorption and recombination coefficients, and an optimization of the threshold current density with respect to the number of wells is given