Wavefunction Engineering

Wavefunction engineering refers to the unprecedented ability to specify the localization of carrier wavefunctions in quantum semiconductor heterostructures through control over the growth, geometry, and material composition. We have developed computational methods based on finite element and tight-binding methods which allow us to explore basic issues in quantum mechanics and also to design new devices in which specific optical or electronic properties can be optimized. Localization of carriers above barriers has opened up the spectroscopy of above barrier states whose role in designing devices is being explored. Energy levels, energy dispersion relations, optical matrix elements, nonlinear optical coefficients, and lifetimes -- all of these properties of a physical semiconductor system can be optimized in quantum wells. Our proposal of a type-II interband quantum cascade laser avoids the losses due to phonon assisted transitions in the multiple cycling of carriers. Preliminary results for four-constituent InAs/GaInSb/InAs/AlSb Type-II quantum well laser at 3.4 micron wavelength, designed by wavefunction engineering, has alread yielded record-breaking maximum operating temperatures (uptto 285K), demonstrating the efficacy of the computational modeling. Our investigation of the removal of accidental degeneracy in quantum wires of square cross-section, and the control over the optical nonlinearity in stacked quantum wires -- the checker-board superlattice -- are examples of basic and applied physics accessible via wavefunction engineering in laterally confined systems.

Click here for a PostScript version of the article by
L. R. Ram-Mohan and J. Meyer on "Wavefunction Engineering"
(Note:File size ~850Kb)

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