THE EXTRA DIFFERENTIAL GAIN ENHANCEMENT IN MULTIPLE-QUANTUM-WELL LASERS

By accounting for the unavoidable thermal population of injected carriers in the optical confining layers we find that the use of multiple quantum wells (MQW) as active region actually leads to an extra increase in differential gain. Specifically, the maximum differential gain increases with the number of wells in the quantum-well structures. The transparency current density in the MQW structures does not scale as the number of quantum wells. These conclusions are at variance with presently accepted theory and of major implications for the design of high-speed, low-threshold semiconductor lasers.