Ultraviolet (UV) light-emitting diodes (LEDs) with an InGaN multi-quantum-well (MQW) structure were fabricated on a patterned sapphire substrate (PSS) using a single growth process of metalorganic vapor phase epitaxy. In this study, the PSS with parallel grooves along the 1120 sapphire direction was fabricated by standard photolithography and subsequent reactive ion etching (RIE). The GaN layer grown by lateral epitaxy on a patterned substrate (LEPS) has a dislocation density of 1.5 × 10 8 cm −2 . The LEPS-UV-LED chips were mounted on the Si bases in a flip-chip bonding arrangement. When the LEPS-UV-LED was operated at a forward-bias current of 20 mA at room temperature, the emission wavelength, the output power and the external quantum efficiency were estimated to be 382 nm, 15.6 mW and 24%, respectively. With increasing forward-bias current, the output power increased linearly and was estimated to be approximately 38 mW at 50 mA.

Analysis of parasitic cyan luminescence occurring in GaInN blue light-emitting diodes J. Appl. Phys. 112, 074512 (2012) Gallium nitride-based light-emitting diodes with embedded air voids grown on Ar-implanted AlN/sapphire substrate Appl. Phys. Lett. 101, 151103 (2012) Analysis of the external and internal quantum efficiency of multi-emitter, white organic light emitting diodes

Determination of deeplevel parameters by a new analysis method of isothermal capacitance transients J. Appl. Phys. 69, 3072 (1991); 10.1063/1.348569 Refinements in the method of moments for analysis of multiexponential capacitance transients in deep level transient spectroscopy Transient capacitance methods were used to analyze traps occurring in unintentionally doped n-type GaN grown by hydride vapor-phase epitaxy. Studies by deep-level transient spectroscopy (DLTS) and isothermal capacitance transient spectroscopy indicated the presence of three majority-carrier traps occurring at discrete energies below the conduction band with activation energies (.eV) AEl=O.264+0.01, AE2=0.580t0.017, and AE3 =0.665+0.017. The single-crystal films of GaN were grown on GaN formed by metal-organic chemical-vapor deposition and on sputter-deposited ZnO; a similar deep-level structure was found in both types of samples. Pulse-width modulation tests using DLTS to determine the capture rates of the traps showed that the capture process is nonexponential, perhaps due to the high trap concentration. The origins of the deep levels are discussed in light of secondary-ion-mass-spectroscopy analysis and. group theory results in the literature.304

Semipolar (11 22) GaN was achieved by controlling anisotropic growth rates in a maskless r -plane patterned sapphire substrate. Upon optimizing the growth conditions, the growth rate of the GaN layer on etched c-plane-like sapphire was much higher than that on other planes such as the original r -plane sapphire. Singularly ( 1122)-oriented GaN was confirmed when GaN was grown on only the c-plane-like sapphire sidewall. The control of the anisotropic growth rate is useful for growing nonpolar and semipolar layers using maskless patterned substrates.

A {20-21} GaN layer was grown from a c-plane-like sapphire sidewall of a {22-43} patterned sapphire substrate according to the epitaxial relationship between c-GaN and c-sapphire despite {20-21} GaN is not growing on {22-43} sapphire. The as-grown {20-21} GaN layer had an m- and {10-11} facet structure. To improve the {20-21} GaN layer, a wide-terrace was attempted. The defects in the GaN layer were clustered on the m-facets, resulting in a dislocation density of less than 5.6 × 105/cm2 on the {10-11} facets. The {20-21} GaN layer had an excellent photoluminescence spectrum indicating a small number of defects.