MeV energy Lithium ion irradiated crystalline GaAs: an optical study

An optical study of GaAs <1 0 0>, undoped, irradiated with 50 MeV Li-ion at room temperature with a fluence ranging from 1x1011 to 1x1014 ions/cm2 using Pelletron ion beam facility of Nuclear Science Centre (NSC), New Delhi has been carried out in the spectral regions of the fundamental optical absorption and interband transition. The damage induced by the MeV ion in the surface and deep inside the semiconductor has been monitored by determining the ion fluence dependence of the optical constants: absorption coefficient (α), reflection (R), ion-irradiation induced defect density (Ns) and optical energy gap (Eg) in the spectral range 200-2500 nm. The present study reveals that the ion irradiation does not induce significant changes in the surface of a semiconductor. The fundamental optical absorption spectra are, however, greatly modified by MeV energy ion-solid interaction