Resonant injection quantum well lasers

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Abstract
The efficient capture of injected electrons by quantum wells is important for minimizing the threshold currents of quantum well lasers. This is especially true for thin wells, where the electrons may not spend enough time in the wells to lose energy and fall into the confined lasing level. Since the band-gap enhancement is greatest for thin wells, it is highly desirable to design structures for which the electron density in the well region is as high as possible, thus maximizing the probability of scattering and decay into the lasing level. Here, we investigate theoretically several related structures for which the incoming electrons encounter a resonance in the quantum well region, producing an enhanced electron density there. This is achieved by adding a thin high alloy concentration barrier adjacent to the well, and by choosing the alloy concentrations outside the barrier to line up the incoming electrons with a higher resonance in the well. Calculations for the GaAs-GaAlAs case demonstrating the effect are shown. An order of magnitude increase in the electron density in the well, as compared to the simple quantum well, is achieved.