The study of Be and Mg ion implantations in GaN
In this study, both undoped and p-type GaN films are implanted by Mg ions with 55keV and Be ions with 40 keV. The films are then annealed at a temperature range between 600 oC and 1050 oC. Below 800 oC, the lattice structure with the GaN films are difficult to restore. Due to the intrinsic limits of the lamp and sample holder, common rapid thermal annealing (RTA) system can not exceed 1000 oC. The implanted samples are finally annealed in a furnace to obtain the permitted value of resistivity in the Hall measurement. Before thermal annealing, the Atomic Force Microscopic (AFM) measurement is intended to investigate the outside damages on the GaN surface, and the X-Ray diffraction (XRD) measurement is taken to realize the inner GaN stress caused by the introduced ions. Subsequently, the ion distributions in the GaN films are understood by the Secondary Ions Mass Spectroscope (SIMS) measurement. Furthermore, the Fourier Transform Infrared Ray (FTIR) experiments are proceeded to investigate the acceptor-hydrogen complexes in the GaN films, and to observe the activation in the implanted layers, the optics measurements of the implanted undoped samples are taken. In the end of the study, the Hall measurements of the implanted samples after thermal annealing are performed. The electrical behavior of implanted samples conforms to the dependence between the annealing temperature and sheet resistivity. Structural and electrical characterizations of the GaN thin films after thermal annealing show that induced defects in the GaN films dominate over implant doping effects.
|Appears in Collections:||Thesis|