Effect of In implantation and annealing on the lattice disorder and nano-mechanical properties of GaN

Abstract

The effect of 700keV In implantation and subsequent annealing on GaN was studied by Rutherford Backscattering spectroscopy, Raman spectroscopy and nanο-indentation as a function of the ion fluence (F) ranging from 5×1013 to 1×1016cm−2. Symmetry allowed and disorder activated Raman scattering peaks were analyzed using the spatial correlation model, allowing their assignment to phonon branches of crystalline GaN or defects and the estimation of the corresponding phonon coherence length (L). The L values decrease abruptly at a critical fluence of approximately 2×1014cm−2. After a slight increase in the nano-hardness (H) and reduced elastic modulus (Er) values at low implantation fluences, they exhibit a steep reduction. These variations are accompanied by changes in the shape of the load–displacement curves, which are indicative of elasto-plastic behavior up to a critical F, whereas they approach the ideal plastic behavior at higher fluences. Annealing at 1000°C of the sample implanted with 1×1015ions/cm2 results in efficient recovery of its structural and nano-mechanical properties. However, annealing of specimens implanted at higher fluences causes partial recovery that starts mainly from the transition region between the heavily damaged and the underlying undamaged GaN. The highly correlated behavior of L, H and Er on the implantation fluence implies a common origin of the studied effects.