Abstract
In this study, energy band-pass filters composed of superlattice resonance tunnelling structures are proposed. Based on the analogy between electron waves propagating in superlattice structures and electromagnetic waves travelling in transmission lines, the method developed for designing a coupled cavity filter in microwave engineering can be adopted to provide a first-cut design of energy band-pass filter to fulfil specific requirements. The governing equations are derived, and can be used to convert the parameters determined by the microwave technique to the physical dimensions of the quantum well structure. Then, adjustments are made such that the physical dimensions are integer multiples of the monolayer thickness, resulting in a change of the central energy of the pass-band. The potentials of the quantum well are fine tuned to compensate the shift of the centre energy. Designs of Butterworth single-cavity, Butterworth three-cavity and Chebyshev three-cavity energy band-pass filters are presented. The important feature of this energy band-pass filter is that the stop-band of this filter can be very wide so that spurious responses from out-of-band electrons can be reduced.