What is the double heterostructure theory?
The double heterostructure is a concept where a thin layer of a smaller-bandgap semiconductor is sandwiched between two layers of a larger-bandgap semiconductor. This creates a potential well that confines both electrons and holes to the middle layer, increasing their recombination probability and thus light emission. At the same time, the larger-bandgap cladding layers have a lower refractive index, so they act as a waveguide for the emitted light. The beauty of the heterostructure lies in its simplicity: by choosing materials with matching lattice constants, like GaAs and AlGaAs, we can grow defect-free interfaces. This idea, which I first proposed in 1963 and demonstrated with my team in 1970, made possible the first continuous-wave laser diodes at room temperature. It is a perfect example of how fundamental physics—band theory, quantum confinement, and waveguiding—can be harnessed for revolutionary technology.
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