Sequential mechanism of electron transport in the resonant tunneling diode with thick barriers
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ICS OF SEMICONDUCTOR DEVICES
Sequential Mechanism of Electron Transport in the Resonant Tunneling Diode with Thick Barriers N. V. Alkeeva^, S. V. Averina, A. A. Dorofeevb, P. Vellingc, E. Khorenkoc, W. Prostc, and F. J. Tegudec aInstitute
of Radio Engineering and Electronics, Russian Academy of Sciences (Fryazino Branch), pl. Vvedenskogo 1, Fryazino, Moscow oblast, 141190 Russia ^e-mail: [email protected] bPulsar Research Institute, Moscow, 105187 Russia cSolid State Electronics Department, Gerhard-Mercator-University, 47057 Duisburg, Germany Submitted June 6, 2006; accepted for publication June 15, 2006
Abstract—A frequency-dependent impedance analysis (0.1–50 GHz) of an InGaAs/InAlAs-based resonant tunneling diode with a 5-nm-wide well and 5-nm-thick barriers showed that the transport mechanism in such a diode is mostly sequential, rather than coherent, which is consistent with estimates. The possibility of determining the coherent and sequential mechanism fractions in the electron transport through the resonant tunneling diode by its frequency dependence on the impedance is discussed. PACS numbers: 73.40.Gk, 85.30.Mn DOI: 10.1134/S1063782607020212
1. INTRODUCTION Recently, interest in semiconductor mesoscopic structures has significantly increased [1]. First of all, this circumstance is caused by the development of semiconductor technology allowing the fabrication of structures with sizes on the order of a few and tens of nanometers. In such structures, the electron de Broglie wavelength exceeds the structure size, and the transport of electrons is mainly controlled by their wave properties, which results in a large variety of new effects [1]. These effects disappear if the dephasing time of the electron wave function is much shorter than the electron transit time through a structure. The study of mechanisms of carrier transport in mesoscopic structures is an important fundamental problem. One mesoscopic structure is the resonant tunneling diode (RTD) suggested for the first time by Esaki and Tsu [2]; this is one of the first nanoelectronic devices [3]. It consists of a narrow-gap semiconductor layer, i.e., quantum well (QW), arranged between two semiconductor layers (barriers) with a wider band gap. These layers are in turn arranged between layers (spacers) of a lightly doped narrow-gap semiconductor followed by heavily doped emitter and collector layers. One or several size-quantization levels arise in the QW. As a bias voltage is applied, the current through the RTD flows only when the emitter contains electrons which can resonantly (i.e., with conservation of energy and transverse momentum) be tunneled to the QW level and further to the collector. The RTD features a very fast response; e.g., it is known that its nonlinear proper-
ties are retained up to ~10 THz [4]. The RTD has other unique properties: in particular, it is the only nanoelectronic device operating at room temperature, and its current–voltage (I–V) characteristic contains negative differential conductance (NDC) portions. Initially [2],
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