Optical properties of wide bandgap III-nitride- and zinc oxide-based epilayers, alloys, and heterostructures

Scope and method of study. The optical properties of the III-Nitrides and ZnO were studied using a variety of spectroscopic experimental techniques. The semiconductor samples studied included epilayers, bulk crystals, alloys, and heterostructures. A large variety of picosecond and nanosecond laser systems as well as continuous wave light sources were used to optically excite the samples in this study. The sample emission was detected with photomultiplier tubes, CCD cameras, and optical multichannel analyzers in conjunction with spectrometers.; Findings and conclusions. The binding energy for intrinsic excitons in GaN was determined. The effect of strain on these excitons was studied. The optical properties of InGaN alloys were investigated. The characteristics of AlGaN and InGaN alloys as a function of pressure were studied. The dynamical behavior of photoexcited carriers in AlGaN/GaN double heterostructures was explained. The stimulated emission from AlGaN/GaN separate confinement heterostructures was studied as a function of the excitation wavelength. A comparison of the emission from highly-excited (In,Al)GaN thin films and heterostructures was performed. The results obtained suggest that the group-III Nitrides and ZnO are excellent candidates for the development of ultraviolet optoelectronic devices. Several important optical parameters are provided, which are critical for understanding and designing efficient devices.