| In this dissertation, the growth of III-Nitride based ultraviolet (UV) emitters by molecular beam epitaxy has been addressed. These devices can find applications in optical data storage, solid-state lighting, and in biological detection. A significant part of the research involved materials development, as there are several major scientific and technological hurdles that must be overcome in order to produce commercially viable devices.; For emission in the wavelength region 330 nm to 350 nm, the devices were designed as electrically-injected light emitting diodes (LEDs). Each layer of this structure was individually optimized to improve the materials properties. To overcome the difficulties in p-type doping, a new growth regime has been explored which led to films with hole concentrations of up to 2 x 10 18/cm3. Multiple quantum wells (MQWs) were grown along polar and non-polar directions to understand the effects of the presence of built-in polarization fields. It was found that these detrimental effects are minimized for ultra thin wells. Use of an Indium flux as a surfactant was found to substantially improve the luminescence properties of bulk Aluminum Gallium Nitride (AlGaN) alloys and MQWs. UV-LEDs grown under these optimized conditions show an optical power output of 0.75 mW at 340 nm and 4.5 mW at 350nm.; For emission in the wavelength region below 270 nm, due to the difficulty of doping AlGaN alloys with high Aluminum Nitride (AlN) mole fraction, edge or vertical emitting electron beam-pumped laser structures have been developed. Since it is difficult to cleave III-Nitrides deposited onto C-plane sapphire, edge emitting laser structures using a Graded-Index Separate Confinement Heterostructure (GRINSCH) based geometry have been deposited onto A-plane sapphire using a novel AlN buffer layer. An AlGaN bulk film or a set of AlN/AlGaN MQWs is used as the active region. For use in these devices, the growth of high Al content AlGaN was optimized to reduce the deep-level luminescence. In the vertically emitting geometry, highly reflecting AlGaN based distributed Bragg reflectors were used as end mirrors. Electron-beam pumping of a bulk 70% AlGaN alloy in a single-pass surface mode excitation has demonstrated the onset of stimulated emission at 270 nm. |
