Cathodoluminescence and electrical anisotropy from α and β dislocations in plastically deformed gallium arsenide

Abstract

Infrared cathodoluminescence (IR-CL) micrographs were taken of surfaces perpendicular (II2) and parallel (021) to the bend axis [II2] of n-type GaAs single crystals bend at 700°C in four-point bending to introduce α (Ga) and β (As) dislocations. At the bend center, light and dark checkered patterns associated with dislocations could be observed only in the IR-CL micrographs but not by optical, standard infrared, or secondary electron emission microscopy. No significant changes related to the type of dislocation (α or β) or dislocation density were observed either in the IR-CL peak half-width or peak position at E=1.411 eV. However, decreases of 40−70% in the relative IR-CL intensity were observed in the bend samples containing predominantly α or β dislocations. To study electrical anisotropy in the deformed samples, Hall measurements as a function of temperature were made of sections cut parallel and perpendicular to the [II2] bend axis to eliminate effects due to point defects and impurities. The results indicate that relative to the unbent control sample, the conductivity and mobility of sampples with dislocations oriented parallel to the current direction were slightly enhanced, while decreases of 50−60% were noted when the dislocations were aligned perpendicular to the current direction. When oriented in the parallel mode, an increase in conductivity and mobility was noted from both types of dislocations, with the samples containing β dislocations showing a larger increase than those with α dislocations. In contrast, when the dislocations were oriented in the mobility than thoise with β dislocations. The observed electrical anisotropy is discussed in the light of current models describing specular (or difuse) electron scattering dislocations.