Comparison of mid-infrared laser diode active regions

The development of mid-infrared interband diode lasers has been hindered by factors such as Auger recombination and intervalence band absorption, which become increasingly important at longer wavelengths. A number of structures have been proposed in which the effects of these processes are reduced. The maximum gain per unit volumetric current density can be used as a figure of merit for comparing different active region materials. Using this figure of merit, we compare a series of structures with band gaps near 0.3 eV (i.e., wavelengths near 4 microns). The figure of merit is obtained from gain spectra calculated using superlattice Kp theory and a combination of calculated and measured recombination rates. We show that devices based on active regions incorporating type-I InAsSb/AlInAsSb or InAsSb/InAsP quantum wells should have room temperature threshold currents 7-13 times smaller than those of devices based on bulk InAs. However, devices using type-Il superlattice active regions should have room temperature threshold currents that are a factor of 3-4 times smaller than those of the type-I quantum wells. The figure of merit can also be used to determine the optimal thickness of the active region as a function of waveguide loss and optical mode width