Stress Analysis of Strained Superlattices.
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Stress Analysis of Strained Superlattices. R. Peleshchak State Pedagogical University, 24 Franko str., 82100 Drohobych, Ukraine H. Khlyap University of Technology, E.-Schroedinger str. 56, D-67663 Kaiserslautern, Germany, and 8tate Pedagogical University, 24 Franko str., 82100 Drohobych, Ukraine ABSTRACT The latest successful development of smart technologies, in particular, molecular-beam epitaxy technique and pulse-laser deposition method, made it possible to manufacture optoelectronic active elements based on semiconductor materials with sufficient mismatch of the lattice parameters. This problem is of special interest for preparing photosensitive devices with strained superlattices. The paper focuses on the analysis of charge carriers behavior in mechanically strained superlattices based on semiconductor materials from A2B6 and A4B6 (ZnSe, ZnTe and PbS) playing an important role in the optoelectronics design. Computational modeling is settled on the solution of one-dimensional Schroedinger equation. INTRODUCTION The development and improvement of novel growth technologies (in particular, molecular-beam epitaxy) have made it possible to produce extremely high-quality epitaxial interfaces, not only between lattice-matched semiconductors, but even between materials which differ in lattice constant by several percent. Such a lattice mismatch can be accommodated by uniform lattice strain in sufficiently thin layers [1]. The resulting so-called “pseudomorphic” interface is characterized by an in-plane lattice constant which remains the same throughout the structure. These strains can cause profound changes in the electronic properties, and therefore provide extra flexibility in device design. Knowledge of the discontinuities in valence and conduction bands at semiconductor interfaces is essential for the analysis of the properties of any heterojunction. Our paper aims to analyze photoluminescent and electric field-induced properties of the heterostructures PbS/ZnSe, PbS/ZnTe taking into account strain and deformation phenomenon occurred under the growth of the structures. EXPERIMENTAL DETAILS The investigated PbS/ZnSe and PbS/ZnTe heterostructures were grown by the MBE technology of lead sulfide films on the (110)-oriented ZnSe and ZnTe wafers of 1 mm thickness with a substrate temperature Ts = 540 K (the vacuum level in the effusion cell was estimated to be about 10-9 Torr). The thickness of PbS films was about 1 µm. The mismatch of lattice parameters of contacting materials was estimated to be about 4%. The main parameters of the contacting materials are presented in the Table 1. Some elastic values for the materials are presented in the Table 2. The first experimental results were obtained under the photoluminescence investigations according to the method [2] in order to clarify the dimensions of the region where the elastic and deformation effects make considerable contribution. The investigated structures (as a model the superlattice PbS/ZnSe was selected) were illuminated from the side of the substrate
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