Formation of Embedded Nitride Semiconductor Nanocrystals.

Ion Implantation;Gallium Nitride;Indium Nitride;Nanocrystal;Ion Beam Synthesis;Materials Science and Engineering;Physics;Engineering;Science;Physics

Wood, Adam W.Uher, Ctirad ;

University of Michigan

关键词: Ion Implantation;    Gallium Nitride;    Indium Nitride;    Nanocrystal;    Ion Beam Synthesis;    Materials Science and Engineering;    Physics;    Engineering;    Science;    Physics;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/91523/adamww_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

In this thesis, the formation, phase selection, and spatial positioning of GaAs:N(InAs:N) nanocomposite layers produced by N-implantation, focused ion beam (FIB)irradiation, and rapid thermal annealing (RTA) of GaAs (InAs) were investigated.To examine nanocrystal formation mechanisms, the influence of annealingtemperature and annealing time on phase formation in GaAs:N were examined. For RTAtimes of 30 s, we observed the nucleation of zincblende (ZB) GaN at temperatures of 650to 900ºC. For furnace anneal (FA) times of 10 min, wurtzite (WZ) GaN nucleation wasobserved for anneal temperatures as low as 650ºC. In the case of InAs:N, for RTA at500-550ºC ZB InN nanocrystals were nucleated. However, RTA temperatures of 600ºCled to the nucleation of WZ InN nanocrystals with a larger average diameter. Theseresults indicated the key role of annealing time and temperature on crystallite nucleation.A TTT diagram was developed for GaN nucleation in ion-implanted GaAs. The TTTdiagram provides an annealing schedule for the selective formation of ZB and WZ GaN.The formation mechanisms for nucleation of ZB and WZ GaN (InN) wereinvestigated and a thermodynamic model for the preferential nucleation of the ZB phasewas proposed. ZB nanocrystals had a higher density of low-energy surface planes, whichdrove the adoption of the ZB phase for sufficiently small nuclei. We demonstrated thefirst nucleation of ZB and WZ InN in InAs using ion-implantation followed by thermalannealing.Finally, a new process for simultaneous nanostructuring and phase selection,termed ;;directed matrix seeding,” was demonstrated. Broad-area N+ implantation ofGaAs followed by rapid thermal annealing led to the formation of nanocrystals at thedepth of maximum ion damage. With additional irradiation using a Ga+ focused ionbeam, selective lateral positioning of the nanocrystals within the GaAs matrix wasobserved in isolated regions of increased vacancy concentration. Following rapid thermalannealing, the formation of zincblende GaN was observed in the regions of highestvacancy concentration. The directed matrix seeding process offers a method for preciselycontrolling the phase and spatial location of embedded nitride nanostructures in a varietyof host materials.