| III-nitride photonic devices offer benefits such as UV/blue emission, large band offsets of InN/GaN/AlN heterostructures allowing novel quantum well (QW) device design, and inherently high emission efficiencies. Furthermore, due to their mechanical hardness and larger band gaps, III-nitride based devices may operate at much higher temperatures and voltages/power levels and are expected to provide much lower temperature sensitivities. These are crucial advantages for many applications.; New physical phenomena and properties are expected to dominate as the device size scales down. The micro-size light emitters offer benefits over edge-emitters such as the ability to create arrays of individually controllable pixels on a single chip, enhanced quantum efficiency, and greatly reduced lasing threshold. Micro and nano photonic structures and devices based upon III-nitride wide band-gap semiconductors were designed, fabricated and characterized. Individual microdisk blue-light-emitting diodes (mu-LEDs) of varying diameters from 5 to 20 mum have been fabricated from InGaN/GaN quantum wells (QW).; Ultraviolet near-field scanning optical microscopy (UV-NSOM) and near-field spectroscopy have been employed to study the optical properties of AlGaN/GaN quantum-well submicron waveguides.; Nanofabrication and characterization of photonic crystals (PCs) with diameter/periodicity as small as 70/150 nm on III-nitride materials has been achieved. An unprecedented maximum optical power enhancement factor of 20 was obtained under optical pumping from PCs on InGaN/GaN MQW. Under current injection, optical power enhancement factors of 2.9, 2.5 and 1.63 were obtained for PC-LEDs at 299 nm UV, 333 nm UV and 460 nm blue emission wavelengths, respectively. Transient responses of III-nitride UV PC-LEDs were measured by pico-second time-resolved electroluminescence (EL) spectroscopy. We have achieved 4-fold enhancement in modulation speed of UV LED by PC formation. The carrier recombination lifetime tauQW of the LED and the surface recombination velocities S of nitride materials were measured.; Polarization resolved electroluminescence (EL) studies of III-nitride blue and UV LEDs were performed. It was found that transverse electric (TE) polarization dominates in the InGaN/GaN MQW blue LEDs. (lambda = 458 nm), whereas transverse magnetic (TM) polarization is dominant in the AlInGaN QW UV LEDs (lambda = 333 nm). This emission property makes nitride UV emitters unique and has direct consequences for its performance. New device design architectures are suggested for overcoming the problems associated with it. |
