No abstract

In this letter, we show that explosive crystallization can occur sequentially along the same laser scan line either from the liquid phase or in the solid phase. Which phase dominates depends on the laser scan speed, the proximity of the a-Si melting isotherm, and the magnitude of the ’’thermal kick’’ provided by fluctuations in laser power or at localized regions of higher absorption.

High mobility electron gases and modulationdoped field effect transistors fabricated in Si/Si1−x Ge x by rapid thermal chemical vapor deposition Formation of βSiC at the interface between an epitaxial Si layer grown by rapid thermal chemical vapor deposition and a Si substrate Chemical vapor deposition has been applied to the fabrication of a relaxed SiGe buffer on (100) Si substrates. Our structures consist of a O%-x% graded layer and a uniform Si 1 -",Ge x capping layer, with x between 32% and 52%. First, the variation of the threading dislocation density with grading rate has been determined. Our results clearly show an abrupt transition between two domains: steep gradings correspond to a high dislocation density, and smooth gradings to low dislocation densities. Second, the surface morphology has been studied at different steps of the buffer fabrication. In addition to the classical (110) crosshatch morphology, we report for the first time (1OO)-oriented undulations. This new morphology, only found on steep gradings, is attributed to a Stranski-Krastanov growth mode caused hy large surface strains. Finally, we propose a new picture of the role of the grading: a steep grading, with a large surface strain, induces very undulated growths; in this case, small dislocation loops and a high density of threading dislocation are generated. Our calculations allow us to derive a simple criterion: grading rates lower than 137% Gel j-Lm will guarantee a relaxation of the low mismatched type. Following this, very low threading dislocation densities (l0 3 cm -2) were indeed achieved.

Thin metallic silicide films epitaxially grown on Si(111) and their role in Si-metal-Si devices

Impurity segregation in explosively crystallized a-Si presents two different behaviors depending on whether the intermediate liquid phase in the explosive process is large or narrow. This confirms the theories already published. In other words, a-Si explodes in a way similar to a-Ge. a-Si, however, presents a specific type of explosive crystallization explained by its higher nucleation rate with respect to a-Ge.