We report on a deep UV light-emitting diode over sapphire substrate with AlGaN multiple-quantum-well active region. Pulsed atomic-layer epitaxy deposited low-defect AlN/AlGaN buffers and an optimized active layer design yielded a sharp quantum-well emission peak at 287 nm and very little long-wave secondary emission. For a 100 μm×100 μm unpackaged device, a power of 27 μW at 20 mA dc and a peak external quantum efficiency of 0.1% at 100 mA pulse pumping were measured. Flip-chip packaging should increase these numbers nearly by a factor of 3.
We report for the first time on the RF performance of a low-threshold AlGaN/GaN metal–oxide–semiconductor heterostructure field transistor (MOSHFET) with zirconium dioxide as the gate dielectric. Low gate leakage current of 5×10-7 A/mm2 and a threshold voltage which was only 1 V higher than that of an HFET were achieved. The RF power of these devices at 2 GHz was 14.32 W/mm at 50 V drain bias.
We report on the strain reduction in AlGaN layers grown on porous GaN (P-GaN) by metalorganic chemical vapor deposition (MOCVD). The P-GaN was obtained by ultraviolet radiation-enhanced electroless wet chemical etching of thick hydride vapor phase epitaxial grown GaN (HVPE-GaN) templates over (001) sapphire substrates. By optimizing the growth conditions, lateral growth of AlGaN was enhanced resulting in air-bridge formation between the P-GaN and the AlGaN layers. X-ray diffraction studies showed significant strain relaxation in AlGaN layers primarily due to the strain sharing between P-GaN and the AlGaN layers. This allowed us to grow crack-free good optical quality layers with thickness exceeding the critical limits for AlGaN deposition on the conventional MOCVD GaN or HVPE-GaN. The obtained results demonstrate the potential of this approach for the development of efficient ultraviolet light emitters.
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