Superlattices and Microstructures, Vol. 22, No. 2, 1997 High-field transport in superlattices: observation of the Stark-cyclotron resonance Luca Canali†, Fabio Beltram‡ Scuola Normale Superiore and Istituto Nazionale per la Fisica della Materia, I-56126 Pisa, Italy Marco Lazzarino, Lucia Sorba§ Laboratorio TASC dell’Istituto Nazionale per la Fisica della Materia, I-34012 Trieste, Italy (Received 15 July 1996) Electron transport in heterojunction superlattices under intense electric and magnetic fields is investigated. In the case of parallel fields, current resonances are shown for particular ratios of electric and magnetic fields satisfying the Stark-cyclotron resonance (SCR) condition. At SCR the potential drop per period is an integer multiple of the magnetic quantization energy and elastic tunneling transport between Landau levels belonging to neighboring wells becomes possible. Unambiguous demonstration of SCR in an appropriately tailored GaAs/AlGaAs superlattice is given for transitions involving up to four Landau-level index change. In the case of orthogonal electric and magnetic fields, a substantial suppression of the miniband current is reported. This is due to the magnetic-field induced localization of superlattice electronic states. c  1997 Academic Press Limited Semiconductor superlattices (SLs) have been the system of choice for the study of quantum transport in periodic potentials since their introduction in the seventies [1]. Transport in the high electric-field limit was analyzed both theoretically [2] and experimentally [3] leading to the demonstration of negative differential conductance (NDC) for fields exceeding a critical electric field F c = ¯ h /ed τ , where d is the SL period and τ is the momentum relaxation time. This NDC stems from the field-induced localization of miniband states predicted by Wannier [4] and demonstrated experimentally by Mendez et al. [5]. In fact, for fields larger than F c , eigenvectors of a periodic system (supposed 1D for simplicity) are the so called Wannier– Stark states, localized over the Wannier-length L W = /eF , where  is the miniband dispersion. The corresponding eigenvalues form a ladder: E ν = E 0 − eFd ν , where ν = 0, ±1,... is the well-number index. Here we want to discuss the case where an additional intense magnetic field is applied along the SL growth † Present address: Applied Physics Department, Lorentzweg 1, 2628 CJ Delft, The Netherlands. ‡ and Laboratorio TASC dell’INFM, I-34012 Trieste, Italy. § Also with CNR-ICMAT, Montelibretti, Roma, Italy. 0749–6036/97/060155 + 05 $25.00/0 sm960303 c  1997 Academic Press Limited