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 it is found that the use of MQW's (multiple quantum wells) as active regions actually leads to an extra increase in differential gain. Specifically, the maximum differential gain increases with the number of wells in the QW structures. The transparency current density in the MQW structure does not scale as the number of QWs. These conclusions are at variance with presently accepted theory and have major implications for the design of high-speed, low-threshold semiconductor lasers.