Investigations on the effect of argon ion bombardment on the structural and optical properties of crystalline gallium antimonide

Abstract

The effects of bombardment of 250 keV argon ions in n-type GaSb at fluences 2×1015 and 5×1015 ions cm−2 were investigated by high-resolution X-ray diffraction (HRXRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). HRXRD studies revealed the presence of radiation-damaged layer (strained) peak in addition to the substrate peak. The variation in the lattice constant indicates the strain in the bombarded region. The out-of-plane (ϵ⊥) and in-plane strains (ϵ|) determined from the profiles of several symmetric and asymmetric Bragg reflections, respectively, were found to change with the ion fluence. Simulations of XRD patterns using dynamical theory of X-ray scattering (single-layer model) for the damaged layer yielded good fits to the recorded profiles. FTIR transmission studies showed that the optical density (α·d) of GaSb bombarded with different fluences increases near the band edge with increase in ion fluence, indicating the increase in the defect concentration. The density of the defects in the samples bombarded with different fluences was in the range of 3.20×1021–3.80×1021 cm−3. The tailing energy estimated from the transmission spectra was found to change from 12.0 to 58.0 meV with increasing ion fluences, indicating the decrease of crystallinity at higher fluences. SEM micrographs showed the swelling of the bombarded surface of about 0.33 μm for the fluence of 2×1015 ions cm−2, which increased to 0.57 μm for the fluence of 5×1015 ions cm−2.