Semiconductor superlattice interference filter design

The quantitative analogies that have been previously established [J. Appl. Phys. 65, 814 (1989)] between electron wave propagation in semiconductors and optical wave propagation in dielectrics may be used to translate thin‐film optical device designs into semiconductor superlattice device designs. The procedure for this direct mapping is also described in the above reference. The resulting designs, however, have compositions that are not constrained to be within a usable compositional range and they have layer thicknesses that are not constrained to be integer multiples of a monolayer thickness. In the present work, a systematic design procedure is presented that includes these required practical constraints. This procedure is then applied to the design of Ga_1−xAl_xAs superlattice narrow interference filters. For pass kinetic energies in the range of 0.14–0.20 eV, compositions (values of x) and numbers of monolayer thicknesses needed to produce quarter‐wavelength layers are calculated. The detailed design of an example narrow bandpass (15.4 meV) filter with a pass electron energy of 0.20 eV is presented.