Unrelaxed State in Epitaxial Heterostructures Based on Lead Selenide

Arif Pashaev,Megi Enukashvili,Vladimir Zlomanov,Omari Davarashvili,Revaz Gulyaev,Zaira Akhvlediani

doi:10.4236/jmp.2012.36068

Arif Pashaev, Megi Enukashvili + Show 4 more

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https://doi.org/10.4236/jmp.2012.36068

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Abstract

The work deals with the epitaxial PbSe layers grown on the KCl substrates by the method of “hot-wall” molecular epitaxy over the range of layer thicknesses of 20 - 2000 nm. Special emphasis is put on the values of elastic deformations that could be generated and frozen in epitaxial layers with the aim of influencing their energy spectra and optical properties. The maximum deformation at layers tension made up 57% of the initial mismatch between the layer and the substrate (ε = Δa/a = 0.015). In such a solid-state structure effective “negative” pressure is realized, which is justified by increase in the tangential lattice constant and the forbidden gap width. This width correlates with the tangential lattice constant (deformation) and corresponds to certain values of definite frequencies of direct electron transitions across the forbidden gap.

Highlights

Semiconductor layers at mismatch with the substrate >0.01 are a promising field of the physics and materials science of semiconductors.In epitaxial heterostructures, the strained state depends on the lattice mismatch and the difference between the thermal coefficients of expansion of the substrate and the epitaxial layer
At the thickness of 20 nm, the deformation ε makes up 57% of the initial mismatch of PbSe with the KCl substrate
Thin strained PbSe layers were grown on the KCl substrates by the method of “hot-wall” molecular epitaxy

Summary

Introduction

Semiconductor layers at mismatch with the substrate >0.01 are a promising field of the physics and materials science of semiconductors.In epitaxial heterostructures, the strained state depends on the lattice mismatch and the difference between the thermal coefficients of expansion of the substrate and the epitaxial layer. In the result of the shift of energetic bands and subbands because of deformations in strained layers the forbidden gap width changes In this connection, narrow-gap IV-VI semiconductors, characterized by a significant relative change of the forbidden gap under elastic stress, are of interest [1]. If the layers of IV-VI semiconductors are grown on the substrates with a larger lattice constant under the conditions of their stretching, and not contracting, by the substrate, i.e. under the conditions of effective “negative” pressure, the forbidden gap width may increase significantly. When such layers are doped with Cr, In, Yb, the shift of their levels to the depth of the forbid-

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Discussion

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