Electron microscope investigation of damage structure in gallium-arsenide bombarded with neon ions

Abstract

Transmission electron microscopy studies of thin films of gallium arsenide have shown that the surface regions become non-crystalline (i.e. amorphous) after bombardment at 21 °C with Ne²⁰ ions of energies between 40 and 100 keV. This effect occurs after ion doses of about 1 × 10¹⁵ ions cm⁻¹ and the damaged material recrystallizes onto the underlying single crystal in an apparently epitaxial manner during post-bombardment annealing at temperatures between 270 °C and 300 °C. Annealing at temperatures up to ∼700°C in an inert atmosphere causes growth of dislocation loops which result from the initial damage structure. These dislocations have not been studied in detail due to the occurrence of complicating structure which results from the dissociation of GaAs at temperatures above ∼400 °C. GaAs which was bombarded with ∼3 × 10¹⁶ 60 keV Ne²⁰ ions cm⁻² while held at different temperatures between 35° and ∼200 °C contained a dense network of dislocations and dislocation loops, but did not become amorphous. However, bombardment at 40 °C with 10¹⁷ 60 keV Ne²⁰ ions cm⁻² did produce an amorphous surface phase.