Abstract
The capabilities of X-ray diffuse scattering (XRDS) method for the study of microdefects in semiconductor crystals have been overviewed. Analysis of the results has shown that the XRDS method is a highly sensitive and information valuable tool for studying early stages of solid solution decomposition in semiconductors. A review of the results relating to the methodological aspect has shown that the most consistent approach is a combination of XRDS with precision lattice parameter measurements. It allows one to detect decomposition stages that cannot be visualized using transmission electron microscopy (TEM) and moreover to draw conclusions as to microdefect formation mechanisms. TEM-invisible defects that are coherent with the matrix and have smeared boundaries with low displacement field gradients may form due to transmutation doping as a result of neutron irradiation and relaxation of disordered regions accompanied by redistribution of point defects and annihilation of interstitial defects and vacancies. For GaP and InP examples, a structural microdefect formation mechanism has been revealed associated with the interaction of defects forming during the decomposition and residual intrinsic defects. Analysis of XRDS intensity distribution around the reciprocal lattice site and the related evolution of lattice constant allows detecting different decomposition stages: first, the formation of a solution of Frenkel pairs in which concentration fluctuations develop, then the formation of matrix-coherent microdefects and finally coherency violation and the formation of defects with sharp boundaries. Fundamentally, the latter defects can be precipitating particles. Study of the evolution of diffuse scattering iso-intensity curves in GaP, GaAs(Si) and Si(O) has allowed tracing the evolution of microdefects from matrix-coherent ones to microdefects with smeared coherency resulting from microdefect growth during the decomposition of non-stoichiometric solid solutions heavily supersaturated with intrinsic (or impurity) components.
Highlights
Among the problems faced by the technologies of semiconductor single crystals with preset properties that are determined mainly by the structural perfection and homogeneity of the crystals, there are important issues relating to the origins and properties of microdefects in their crystal lattice as well as microdefect study and nondestructive control methods
In ion implanted tungsten single crystals, this method revealed and allowed studying 3 nm radius dislocation loops of vacancy and interstitial type [8] which are almost irresolvable in transmission electron microscopy (TEM) images
Analysis of the results showed that the X-ray diffuse scattering (XRDS) method is a highly sensitive and information valuable tool for studying early stages of solid solution decomposition in semiconductors
Summary
Among the problems faced by the technologies of semiconductor single crystals with preset properties that are determined mainly by the structural perfection and homogeneity of the crystals, there are important issues relating to the origins and properties of microdefects in their crystal lattice as well as microdefect study and nondestructive control methods. Hereinafter we will consider microdefects to be local violations of crystal lattice periodicity caused by clusters of point defects (intrinsic or impurity), dislocation loops or dispersed phase precipitates having submicron or micron sizes. All these violations are first type defects [1] by their effect on X-ray diffrac-. We will dwell upon more detailed aspects of the problem in question: capabilities of the XRDS method paired with precision lattice parameter measurements on a diffractometer with a laboratory-grade X-ray source for the study of microdefects in semiconductor single crystals
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