Diffusion ZnTe:Sn layers with n -type conductivity
- PDF / 181,369 Bytes
- 2 Pages / 612 x 792 pts (letter) Page_size
- 114 Downloads / 238 Views
TRONIC AND OPTICAL PROPERTIES OF SEMICONDUCTORS
Diffusion ZnTe:Sn Layers with n-Type Conductivity V. P. Makhny^ and V. I. Grivul Fed’kovich National University, Chernovtsy, 58012 Ukraine ^e-mail: [email protected] Submitted November 10, 2005; accepted for publication November 28, 2005
Abstract—Layers with n-type conductivity equal to ~0.1 Ω–1 cm–1 are obtained by tin diffusion into singlecrystal ZnTe substrates. The origin of electrically and optically active centers in the ZnTe:Sn samples is discussed. PACS numbers: 66.30.Jt, 68.35.Fx, 78.55.Et DOI: 10.1134/S1063782606070062
Production and study of wide-gap II–VI semiconductor compounds that feature a unique set of physicotechnical parameters represents one of the most important challenges in optoelectronics [1]. However, the potential of practical use of these materials is often limited by difficulties related to intentional control of electrical properties of the II–VI compounds. This circumstance is mainly caused by a high concentration of uncontrolled impurities in the bulk samples of these semiconductors and also by their tendency towards self-compensation. The latter factor brings about the preferential monopolar electrical conductivity (σ) of these compounds (except for CdTe); as a result, traditional technologies for controlling the value and type of conductivity are limited in their use. The aforementioned problems were considered in detail in [2] taking into account the effect of intrinsic crystal-lattice defects on σ. An analysis of theoretical results made it possible cr to conclude that there are critical temperatures T n, p for materials with n- and p-type conductivity; the equilibrium methods of annealing at temperatures higher than cr T n, p give no way of changing the conductivity type [2]. We call attention to the fact that anomalously low cr critical temperatures ( T p ≤ 700 K) cannot provide the necessary coefficients of diffusion and solubility for acceptor impurities in the crystals of wide-gap II–VI compounds. As a consequence, it is difficult to obtain a high concentration of free holes in sulfoselenides of cadmium and zinc. At the same time, much larger values of cr cr T n, p ( T n ≈ 1200–1500 K) provide activation of diffusion processes, which is widely used for controlling the electron conductivity σn in the II–VI compounds by annealing in the presence of intrinsic and/or doping elements [3, 4]. Zinc telluride is an exception; the above methods cannot be used to attain a high electron conductivity in this material. The lowest resistivity ρn ≈ 105 Ω cm was obtained for the samples that contained
both excess zinc and the Al donor impurity [5, 6]. In this study, we managed to obtain the diffusion ZnTe:Sn layers with a much lower resistivity (ρn ≈ 10 Ω cm); we also analyzed the main electrical and optical properties of these layers. The starting zinc telluride crystals were grown by the Bridgman–Stockbarger method from the stoichiometric melt and featured the low p-type conductivity (σp ≈ 10–6 Ω–1 cm–1) in the vicinity of room temperature.
Data Loading...
