Electrical properties of isotype N + -GaSb/n 0 -GaInAsSb/ N + -GaAlAsSb type-II heterojunctions
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CONDUCTOR STRUCTURES, INTERFACES, AND SURFACES
Electrical Properties of Isotype N+-GaSb/n0-GaInAsSb/N+GaAlAsSb Type-II Heterojunctions M. A. Ahmetoglu (Afrailov)a^, I. A. Andreevb^^, E. V. Kunitsynab, M. P. Mikhailovab, and Yu. P. Yakovlevb aDepartment
of Physics, Uludag University, 16059 Gorukle, Bursa, Turkey ^e-mail: [email protected] bIoffe Physicotechnical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia ^^e-mail: [email protected]. ru Submitted May 24, 2006; accepted for publication June 7, 2006
Abstract—Band diagrams and current–voltage and capacitance–voltage characteristics of isotype N+-GaSb/n0-GaInAsSb/N+-GaAlAsSb heterostructures have been studied. Dark-current flow mechanisms have been analyzed. It is shown that a staggered type-II heterojunction can behave as a Schottky diode and its current–voltage characteristics exhibit rectifying properties over the entire temperature range 90–300 K. The thermionic-emission current predominates at high temperatures and low voltages. This current is due to thermal excitation of electrons from GaInAsSb to GaSb over the barrier at the heterointerface. A comparison of the relevant theoretical and experimental data confirmed that the tunneling charge transport mechanism plays the key role at low temperatures under both forward and reverse biases. PACS numbers: 73.40.Kp, 79.40.+z DOI: 10.1134/S1063782607020066
1. INTRODUCTION In recent years, GaSb/GaInAsSb heterostructures have been attracting researchers’ attention as promising materials for optoelectronic devices operating in the spectral range 1.5–4.8 µm. These heterostructures have been used to develop high-efficiency light-emitting diodes [1–3] and fast photodiodes [4, 5], which can be used as sensors to detect noxious industrial gases and sources of light for fiber-optic transmission lines of new generation, based on fluorite glasses with exceedingly low loss. The specific features of the band structure of type-II heterojunctions lead to localization of electrons and holes in self-aligned quantum wells on both sides of the heterointerface [6]. The electron affinity and the energy gap of the narrow-gap material vary with the composition of the Ga1 – xInxAsySb1 – y alloy, and, consequently, both staggered and broken-gap type-II heterojunctions can be formed, depending on the extent of band overlapping at the GaSb/Ga1 – xInxAsySb1 – y interface. In staggered type-II heterojunctions (x = 0.24), either the bottom of the conduction band or the top of the valence band of one semiconductor lies outside the band gap of the other material, and the band offsets have the same sign. A broken-gap type-II heterojunction is formed in the heterostructures in the case where neither the bottom of the conduction band nor the top of the valence band of the narrow-gap Ga1 – xInxAsySb1 – y alloy (x ≥ 0.80) lies within the band gap of the wide-gap material [7]. Both electrons and holes penetrate through the interface, and this gives rise to a pronounced band
bending, which hinders the given transport process.
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