An electrochemical etching based on oxalic acid was developed for use in the chemical lift-off of GaN epitaxial structures. It was shown that only the Si-doped n-GaN layer was etched away, while the p-type and undoped GaN layers were not etched at all. The etch rate and the remaining structure were analyzed for various doping concentrations and etching voltages. A lateral etch rate of 12 μm/min was achieved under 60 V for n-type doping concentration of 8×1018 cm−3. This doping selective etching was used to lift-off a GaN epitaxial layer patterned into 300×300 μm2 squares.

Surgery in patients who had Duchenne muscular dystrophy with scoliosis improved function and decreased the rate of deterioration of forced vital capacity compared with patients treated conservatively. However, the muscle power and forced vital capacity decreased in both groups.

A GaN air bridge was fabricated by electrochemical etching and was used as a template for the regrowth of an InGaN quantum well ͑QW͒. Raman spectroscopy confirmed that the GaN membrane on the air bridge relieved part of its compressive strain, and its effect on the InGaN growth was studied. A -photoluminescence ͑PL͒ measurement showed a large blueshift of band-to-band emission for the QW grown on the air bridge. The small residual strain reduced the indium fluctuation during the growth of the InGaN QW and resulted in a low defect density and low activation energy of emission intensity. As a result, the QW grown on the air bridge had a better internal quantum efficiency as measured by temperature-dependent PL.GaN and its related materials opened a new era of light emitting diode ͑LED͒ technology after the realization of blue and green emissions. Presently, GaN-based LEDs are widely used in lighting, automobiles, and display backlights. In spite of the success of high brightness LEDs, GaN has suffered from inherent drawbacks, including the lack of lattice-matched substrates with good thermal and electrical conductivities. Primarily, GaN-based devices are grown on sapphire substrates, and mismatches of the lattice constant and thermal expansion coefficient between GaN and sapphire cause compressive stress in an epitaxially grown GaN layer. 1 The accumulated strain could cause detrimental strain relaxation and defect generation when combined with the growth of highly strained InGaN. 2 An InGaN quantum well ͑QW͒ is primarily used as an active region of blue and green LEDs; however, its growth behavior is quite complicated due to factors including the large lattice mismatch in the GaN-InN system and high indium vapor pressure at the growth temperature. 3 In addition, there have been reports that buffer layers below the active region with different levels of strain could affect the indium incorporation and result in different emission wavelengths. 4,5 For example, Nanhui et al. demonstrated improved optical quality with a strain-controlled buffer layer. 6 Therefore, in this study, we considered what would occur if InGaN QWs were grown on a totally different type of substrate and buffer layer.A GaN air bridge is a freestanding membrane made by deep undercut etching. Due to its flexibility, it removes a portion of the stress in GaN grown on a sapphire substrate. The quality of the epitaxial layer grown on the air bridge is of great concern in electronic and optical device applications. There have been interesting studies on the characterization of InGaN QWs embedded in GaN membranes detached by laser lift-off ͑LLO͒. 7,8 Yu et al. observed a partial reduction in compressive strain and piezoelectric fields of pregrown InGaN QWs after LLO, 7 and enhanced cathodoluminescence efficiency was reported for a similar structure by Li et al. 8 However, no study has been conducted on the luminescence properties of InGaN QWs grown on a GaN air bridge membrane. It gives a better understanding of the InGaN growth mechanism and better co...

A self-formed and ordered anodized aluminum oxide (AAO) nano pattern has generated considerable interest in both scientific research and commercial application. However, the interpore distance obtainable by AAO is limited by 40–500 nm depending on electrolyte and anodizing voltage. It's believed that below-30 nm AAO pattern is a key technology in the fabrication semiconductor nano structures with enhanced quantum confinement effect, so we worked on the reduction of interpore distance of AAO with a novel electrolyte. AAO nano patterns were fabricated with mixed H2SO4 and H3PO4 as an electrolyte for various voltages and temperatures. The interpore distance and pore diameter of AAO were decreased with reduced anodizing voltage. As a result, an AAO nano pattern with the interpore distance of 27 nm and the pore diameter of 7 nm was obtained. This is the smallest pattern, as long as we know, reported till now with AAO technique. The fabricated AAO pattern could be utilized for uniform and high density quantum dots with increased quantum effect.