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Pulsed Laser Deposition of High Quality ZnTe Films Intended for Creating Low-Dimensional Semiconductor Heterostructures |
Viktor K. Savchuk 1, Bohdan K. Kotlyarchuk 1, Rostyslav I. Lesyuk 1, Maciej Oszwaldowski 2 |
1. Institute of Applied Problems of Mechanics and Mathematics (IAPMM), 3B Naukova Str., Lviv 79060, Ukraine |
Abstract |
Rapid progress in developing the producing technologies of semiconductor structures during the last years has enabled researchers to create structures with low-dimension scales (a few nanometers). In this case, the quantum properties of current carriers in such semiconductor structures play key role for determination of their main parameters. Such semiconductor heterostructures can be designed from semiconductor thin films with submicron thickness. However, the principal limitations of the traditional technologies do not enable the growing of semiconductor heterostructures with: a detailed control of the stochiometrical composition; high crystalline quality at a significantly lowered substrate temperature; narrow and well-defined profiles between separate films. Moreover, the ratio “cost/efficiency” is the main technological impediment to progress in the development of technological methods, in the creation of future generations of the elemental base for nanoelectronics, and in the production of atom/molecule scale components. One of the motivations of this research is the development of effective, low-cost and competitive growth technology on the basis of the Pulsed Laser Deposition (PLD) method. It enables to produce a low-dimensional semiconductor heterostructures with the arrays of quantum dots. Such heterostructures can be based on the II-VI semiconductor thin films, where the electron-phonon interaction in three- and two-dimensions is three orders of magnitude stronger than seen in III-V semiconductor heterostructures. Among heterostructures based on II-VI semiconductor compounds, ZnTe/CdTe heterostructure has great potential applications to the realization of efficient lightemitting diodes (LEDs) and photodetectors (PDs), which can operate at higher temperatures in the spectral regions from visible to far-infrared. The ZnTe/sapphire systems can be used in future as complicant substrates for the deposition of CdTe films with submonolayer thickness with the purpose of creating the arrays of quantum dots. Therefore, investigation of the PLD technological conditions with the purpose of growing the high quality ZnTe films on sapphire substrates were carried out. We established that in depending on deposition conditions, PLD method allows to grow the ZnTe films with the rate up to 103 A/sec. Such high instantaneous deposition rates also create an “effective vacuum” of a few orders of magnitude lower. This effect assists in protection of the growing films from impurity by atoms of residual gas of vacuum chamber. We testified that deposition rate is important process parameter, which has great influence on the film properties through the nucleation growth stages. The films were characterized by X-Ray Diffraction (XRD) technique, optical absorption studies, Transmission Electron Diffraction (TEM), the surface morphology and roughness was analyzed by atomic force microscopy (AFM). The thickness of the films was in the range of 0.3-1.5 µm. These XRD analysis and TEM images confirm the decisive influence of the substrate temperature on the quality of crystalline structure of films deposited by PLD method. From XRD measurements was determined the optimal substrate temperature that allows to grown the textured ZnTe thin films. From the optical absorption measurements it was observed that the band gap increased from 2.30 eV – 2.70 eV as the grain size decreased from 100 nm – 20 nm. The surface morphology of ZnTe films deposited at different deposition conditions was examined by AFM. |
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Presentation: Poster at Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth, by Viktor K. SavchukSee On-line Journal of Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth Submitted: 2007-01-12 16:20 Revised: 2009-06-07 00:44 |