Ion-beam-induced Changes On Surface Morphology And Chemical Composition Of In_xGa_1-xN?0.32?x?1.0? Films

In GaN is an important group-?-nitride semiconductor material,which has been widely used for the production of electronic and optoelectronic devices,and has a unique potential for the development of the advanced solar photovoltaic device.The study of ion irradiation effects is of importance to the application of ion implantation techniques in InGa N material as well as the evaluation of radiation resistance for the In GaN-based semiconductor devices.In recent years,our group has been devoted to investigating the ion-beam-induced changes in the microstructures and optical and electrical properties of InGaN films.This thesis presents our results of the investigations on the surface morphology and chemical composition of ion irradiated In GaN.In this work,wurzite InxGa1-xN(0.32?x?1.0)films were irradiated with 5 MeV Xe ions at room temperature(RT)and 500 ?.After irradiation,the surface morphology and chemical composition of the films were investigated by optical microscope(OM),atomic force microscope(AFM),scanning electron microscope(SEM),X-ray energy dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS)and Raman spectroscopy.The effects of annealing at a high temperature(500 ?)were also investigated for the InGaN films irradiated with Xe ions at RT.The results show that:(1)when irradiated with Xe ions to 3×1013 cm-2 at RT,while there are few changes observed on the surface of Ga-rich InxGa1-xN(x<0.5)films,blisters and holes with a diameter of several microns appeared on the surface of In-rich films,which is associated with the formation of N2 bubbles in the irradiated films;(2)the extent of surface damage increased after annealing of the films at 500 ?,which is attributed to the coalescence of the smaller gas bubbles into the larger bubbles during the annealing process;(3)compared to the RT irradiation,less changes of surface morphology were induced by the 500 ? irradiation to 3×1013 cm-2,which is due to the increasing efficiency of defect annealing.However,further irradiation to 6×1013 cm-2 leads to the delamination of the In-rich films from the GaN epilayers;(4)oxidation of metallic atoms on the film surface occurred after irradiation with its extent increased with increasing x in InxGa1-xN;(5)the N atom concentration on the film surface decreased significantly for the In-rich films after irradiation,which is attributed to the formation and release of N2 bubbles.In summary,our results clearly show that the extent of surface damage of InxGa1-xN films induced by ion irradiation increases with increasing x.The results may be of importance for the application of ion beam techniques on the InGaN materials.