Nonpolar m-plane GaN films have been grown by metalorganic vapor-phase epitaxy on patterned a-plane sapphire substrates (diameter: 3 in.) without dielectric masks made of materials such as SiO 2 . The m-plane GaN layer had a smooth and transparent surface over the entire area of the substrate. Furthermore, the epitaxial relationships between the m-plane GaN film and the patterned a-plane sapphire substrate were as follows: ½0001 GaN k ½0001 Sapphire and ½11 20 GaN k ½10 10 Sapphire . The full width at half maximum values of the X-ray rocking curves for ( 1010) GaN along ½11 20 GaN and ½0001 GaN were found to be 396 and 565 arcsec, respectively.

SynopsisThe dynamic recrystallization behavior of austenite in an 18-8 stainless steel and an 18 Ni maraging steel was studied mainly by microstructural observations of the specimens which were water-quenched immediately after the tensile deformation to various strains at temperatures ranging from 800 to 1200 °C and at strain rates of 10'3 10-~ s-1, The changes in austenite grain size and hardness at room temperature due to the dynamic recrystallization were also studied.The deformation conditions for the occurrence of dynamic recrystallization in both steels were made clear as a function of deformation temperature (T), strain rate (~) and strain (e). Dynamic recrystallization takes place under the deformation conditions with Z (Zener-Hollomon parameter) less than the critical value of Z~. Z~ increases as the amount of strain given by the hot deformation is increased or the initial austenite grain size is decreased. The addition o f Cr seems to have the retarding e ffect on the occurrence of dynamic recrystallization of austenite. The dynamically recrystallized grain size (D) is determined only by the deformation condition z, and does not depend on the strain and the initial grain size. D is decreased with increase in Z. The room temperature hardness of dynamically recrystallized austenite in 18-8 stainless steel and the martensite formed from the dynamically recrystallized austenite in 18 Ni maraging steel is higher than that of conventionally heat-treated specimens. However, such an increment of hardness due to dynamic recrystallization is not so large.

The fabrication of a blue m-plane GaInN light emitting diode (LED) grown on an m-plane GaN layer grown on a 3-in. patterned sapphire substrate is reported. The output power of the LED was approximately 3 mW at the wavelength of 461 nm, a driving current of 20 mA, and a forward voltage of 3.5 V. This is the first report of nonpolar or semipolar blue LEDs grown on hetero-substrates with milliwatt scale output power.

Improving current injection into r- and m-planes of nanowires (NWs) is essential to realizing efficient GaInN/GaN multiple quantum shell (MQS) NW-based light-emitting diodes (LEDs). Here, we present the effects of different p-GaN shell growth conditions on the emission characteristics of MQS NW-LEDs. Firstly, a comparison between cathodoluminescence (CL) and electroluminescence (EL) spectra indicates that the emission in NW-LEDs originates from the top region of the NWs. By growing thick p-GaN shells, the variable emission peak at around 600 nm and degradation of the light output of the NW-LEDs are elaborated, which is attributable to the localization of current in the c-plane region with various In-rich clusters and deep-level defects. Utilizing a high growth rate of p-GaN shell, an increased r-plane and a reduced c-plane region promote the deposition of indium tin oxide layer over the entire NW. Therefore, the current is effectively injected into both the r- and m-planes of the NW structures. Consequently, the light output and EL peak intensity of the NW-LEDs are enhanced by factors of 4.3 and 13.8, respectively, under an injection current of 100 mA. Furthermore, scanning transmission electron microscope images demonstrate the suppression of dislocations, triangular defects, and stacking faults at the apex of the p-GaN shell with a high growth rate. Therefore, localization of current injection in nonradiative recombination centers near the c-plane was also inhibited. Our results emphasize the possibility of realizing high efficacy in NW-LEDs via optimal p-GaN shell growth conditions, which is quite promising for application in the long-wavelength region.

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