A study of isotype photosensitive heterostructures (intrinsic oxide)- n -InSe prepared by long-term thermal oxidation
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A Study of Isotype Photosensitive Heterostructures (Intrinsic Oxide)–n-InSe Prepared by Long-Term Thermal Oxidation Z. D. Kovalyuk^, O. N. Sydor, V. N. Katerinchuk, and V. V. Netyaga Frantsevich Institute for Problems in Materials Science, Chernivtsi Branch, National Academy of Sciences of Ukraine, Chernivtsi, 58001 Ukraine ^e-mail: [email protected] Submitted January 15, 2007; accepted for publication January 29, 2007
Abstract—Long-term (for 24–120 h) oxidation of n-InSe crystals in air brings about the formation of a potential barrier, while variation in the conditions of thermal oxidation affects the electrical and photoelectric parameters of the obtained structures. The behavior of current–voltage characteristics for the heterostructures consisting of intrinsic oxide and n-InSe is caused by superposition of the diffusive and shunting currents. Variations in the photosensitivity spectra are related to the formation of the oxide phases such as In2O3 and In2(SeO4)3. It is established that the heterostructure consisting of intrinsic oxide and n-InSe is a structure of the semiconductor– insulator–semiconductor type. PACS numbers: 72.10.Jv, 72.40.+w, 73.40.Ty, 81.65.Mq, 85.60.Dw DOI: 10.1134/S1063782607090096
1. INTRODUCTION
2. EXPERIMENTAL
Laminar crystals of the III–IV group, to which indium monoselenide belongs, attract the attention of researchers first of all in view of the features of their chemical structure. Weak van der Waals coupling of layers makes it possible to easily obtain wafers of these compounds with an arbitrary thickness and with a practically ideal specular surface. These wafers do not require any additional treatments and, therefore, from the practical viewpoint, represent useful objects for the fabrication of heterostructures. Indium selenide (Eg ≈ 1.2 eV) still remains an attractive material for use in high-efficiency photoconverters [1]. It is well known [2] that an alternative method of formation of the potential barrier in the p-InSe crystals consists in thermal oxidation of the substrates in air; this method is simple and inexpensive, in contrast to the traditional method of formation of semiconductor structures. The photoelectric parameters of these heterostructures are also affected profoundly by the conditions of oxidation [3–5]. However, publications concerned with studies of the barrier-formation processes in isotype structures that consist of intrinsic oxide and n-InSe have appeared only recently [6, 7].
We used n-InSe with the concentration of majority charge carriers ~2 × 1013 cm–3 and the charge-carrier mobility of ~400 cm2/(V s) at 300 K as the substrate material. The heat treatment was carried out in the same way as in [4]. As a result, homogeneously colored layers were formed on the wafers’ surfaces; coloring of the layers was governed by the duration of oxidation and indicated that the oxide thickness was different. The maximum thickness of the film was ~0.35 µm. In order to reduce the effect of the series resistance, the thic
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