Photoluminescence and Excitation Studies of Semiconductors

A photolummescence (PL) study of Be and Au ion-implanted GaN is pre­ sented GaN samples were implanted and selectively annealed prior to excita­ tion by a HeCd laser The resulting luminescence was dispersed by a grating spectrom eter and detected using a photomultiplier tube Be is proposed to form a shallow acceptor in GaN and is thus critical to device development and performance From analysis of the PL spectra, a shallow level appears consistently following an annealing procedure It has been observed th a t Au impurities m Si introduce centres near the middle of the bandgap which act as very effective lifetime killers A PL study of the effect of Au impurities m GaN is presented A series of bands occur in the region 1 5eV to 2 4eV with peaks at 1 7eV and 2 3eV A parallel aspect of the work involved the development of a photolu­ mmescence excitation (PLE) spectroscopy system with the ultim ate aim of investigating im purity centres m doped GaN The PLE system consisted of a tunable laser source, existing photolummescence equipment and a computer control / acquisition system PLE is used to investigate the below bandgap optical characteristics of emission bands and levels Prelim inary results using this equipment on well characterised ruby samples are presented along with a study of Be and Au defects m GaN