Shubnikov-de Haas - like oscillations in the vertical transport of semiconductor superlattices

Abstract

Oscillations in the vertical magneto-transport of a GaInAs-AlInAs superlattice were observed and explained as being the modulation of miniband properties. We explain that such a modulation is due to the Landau levels of the highly Si n + doped regions. It is shown that phase and amplitude of these oscillations are dependent on the angle between electric and magnetic elds. This phenomenon is thus similar to the Shubnikov -de Haas e ect in bulk materials, even though the active region of the superlattice is not intentionally doped. Very highly doped three-dimensional regions were grown on each side of the superlattice to allow for the process of Ohmic contact formation.The electronic structure of semiconductor superlattices gave rise to the concept of minibands and minigaps of energy 1 . Due to the newly engineered periodicity, electrons can undergo Bloch oscillations via Bragg reection. Very high-frequency oscillator devices, with superlattices comprising their active regions, have exhibited such behavior. Frequencies as high as 60 GHz with GaAs-AlAs superlattices have recently been reported 2 . GaAs-Ga 1,x Al x As superlattices were often studied in the past, but such materials have been replaced in recent y ears by equivalent GaIn 1,x As xAlIn 1,y As structures, which are more attractive for application in telecommunication devices.Transport properties of superlattices have been extensively studied. There are basically two di erent congurations available for studying transport in superlattices: i when carriers are moving parallel to the layers; or ii when they are moving perpendicular to the layers. Parallel transport properties of superlattices are more frequently studied because in this case better facilities exist for sample processing.Furthermore, very important properties like negative di erential conductance due to negative e ective mass of superlattices occur in the vertical transport regime. Sibille and co-workers observed the negative di erential velocity 3 e ect in undoped short period GaAs-AlAs superlattices. Studying miniband conduction of slightly n + doped superlattices, they then directly observed the bulk-like regime of negative di erential conductance 4 .Superlattices in presence of a magnetic eld applied parallel to the layers have already been studied in detail 5, 6 . E ects such as negative magneto-resistance and in-plane redistribution of electron energy were observed. The in uence of interface uctuations on the vertical miniband transport properties of superlattices has also been observed with the help of a magnetic eld applied in the plane of the layers 7 . E ects of miniband conduction are usually well explained by a semi-classical approach, based on the solution of the Boltzmann transport equation.When the magnetic eld is parallel to the current, no classical e ect is expected to modify the miniband transport properties. However, oscillations of magnetoresistance corresponding to the magneto-phonon e ect have been observed for GaAs-Ga 1,x Al x As superlattices 8, 9 . Such an e ect corre...

Calculation of vertical and horizontal mobilities in InAs/GaSb superlattices

“…However, vertical mobilities are not measured routinely since their measurement requires nonstandard and indirect experimental techniques such as the geometric magneto-resistance. 11,12 Indeed, what is known about vertical mobility is often inferred indirectly from fitting current-voltage data. 13 Here we develop the necessary formalism for the calculation of low-temperature vertical and horizontal mobilities and specialize it to the case of InAs/GaSb SLs.…”

Vertical transport in InAs/GaSb superlattices: model results and relation to in-plane transport

“…However, the value of vertical mobility is not measured routinely, as it requires nonstandard and indirect experimental techniques such as geometric magneto-resistance. 3 Indeed, what is known about vertical mobility is inferred indirectly from fitting current-voltage data. 4 In this situation, it is worthwhile to develop a transport model to infer the value of vertical mobility from knowledge of an experimentally measured horizontal mobility.…”