Ion implantation damage in gallium arsenide crystals.

Crystal damage produced by ion implantation in (110) cut gallium arsenide single crystals has been investigated using X-ray diffraction, reflection high energy electron diffraction (RHEED) and electron microscopy. Various ions were employed, Post bombardment annealing was carried out to remove damage from the crystals. Damage-depth profiles of tellurium and cadmium, and room temperature implanted specimens were measured. Annealing of these specimens without protection was carried out to study damage removal. The results proved to be very complicated, including the decomposition of the gallium arsenide, the formation of beta gallium oxide and gallium telluride, and the occurrence of preferred orientation and twinning in gallium arsenide. Comparisons were made with the annealing behaviour of ball-milled gallium arsenide using X-ray diffraction line broadening. The effects of various types of mechanical damage associated with specimen polishing of the gallium arsenide single crystals were also examined. Damage of single crystal gallium arsenide due to tellurium implantation at high temperature was studied using RHEED. The changes in the effects of annealing behaviour of implanted specimens with protective layers of silicon nitride, aluminium and native oxides were also studied. The observations obtained from RHEED were found to be in agreement with those from Rutherford Back Scattering (RBS) experiments. The formation of the dislocation loops of tellurium and tin implanted specimens were studied using transmission electron microscopy (TEM). Some correlations of defects with the electrical properties of the implanted layers were described. Some work was also carried out using mainly X-ray diffraction methods to study damage due to nitrogen implantation into sputtered tantalum thin films (500 A). The effects of post-bombardment annealing were investigated. After implantation, tantalum nitride (TaN) was formed. This recrystallised with increasing annealing temperatures. The formation of TaN was associated with changes in resistivity of the tantalum film