The influence of Al concentration and barrier width on the transmission spectra in GaAs-Al c Ga 1Àc As heterostructure is studied for two different kinds of the generalized Thue-Morse multibarrier systems (GTMS). These structures provide interesting filter properties with regard to effective band-pass or stopband (of extremely low width) circuitry. The first kind of GTMS is suitable for application as a band-pass electronic filter, while the second kind as stopband filter. High Al concentration and large barrier width result in sharp resonances in the transmission spectrum.
IntroductionSince the experimental realization of Fibonacci [1] and Thue-Morse [2] quasiperiodic superlattices (SL), their fascinating physical properties have been a subject of growing interest both from the fundamental point of view as well as for their potential device applications. The competition between localization and delocalization arising out of quasiperiodicity leads to many intriguing features affecting electron conduction like the occurrence of a highly fragmented, self-similar spectrum [3-6] and the tuning of the tunneling current [7]. The fragmentation of the SL minibands could serve as a basis for electronic filters. Fibonacci SL is reported [8] as a good electronic filter because the Fourier spectrum of the transmitted part of a Gaussian wave packet passing through the SL clearly indicates many prominent and sharp peaks. These peaks correspond to the allowed subminibands of the energy spectrum. Recent study [9] on Fibonacci multibarrier systems (FMS) also suggests the use of such quasi-periodic systems in perfect bandpass or band-eliminator (of extremely low width) filter circuitry. It is worth mentioning that most researches have considered FMSs as the archetype of quasiperiodic heterostructures with the studies on electron dynamics [10], Landauer resistance [11], dc conductance [12,13]. The importance of another quasiperiodic system, Thue-Morse multibarrier system (TMS), over FMS lies in the fact that TMS exhibits better transport