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Herein, the characteristics of AlN epilayers grown directly on hole‐type patterned sapphire substrate (HPSS) by hydride vapor‐phase epitaxy (HVPE) are reported. To investigate the effect of HPSS, the threading dislocation densities (TDDs) of AlN films grown simultaneously on HPSS and flat sapphire substrate (FSS) are analyzed by transmission electron microscopy. The corresponding TDD is measured to be 4.38 × 108 cm−2 for the AlN sample grown on HPSS, which is significantly lower than the value of 1.48 × 109 cm−2 on the FSS. The usability of the AlN/HPSS template for deep ultraviolet (DUV) light‐emitting diodes (LEDs) is proven by growth of AlGaN‐based LED structure emitting at 278 nm with single peak emission in a metal‐organic chemical vapor deposition reactor. The light output power of flip‐chip LED grown and fabricated on AlN/HPSS template is enhanced by a factor of 1.25 when compared with LED on AlN/FSS template at 350 mA injecting current. These results suggest that the high‐quality AlN template grown on properly designed HPSS by HVPE can make a significant contribution toward the realization of highly efficient nitride‐based DUV‐LEDs. [ABSTRACT FROM AUTHOR]

In this paper, comparison between back-illuminated p-i-n AlGaN-based ultraviolet photodetectors (UV-PDs) with and without an n-AlGaN inserted layer is carried out. The results show that the introduction of n-AlGaN interlayer significantly reduces the dark current of AlGaN-based UV-PDs. The mechanism involved is clarified and can be attributed to the role of n-AlGaN interlayer which depletes to isolate the leakage paths generated by dislocations of AlGaN material. Besides, it also greatly improves the spectral performances of the p-i-n AlGaN-based UV-PDs, which can be related to the additional built-in electric fields introduced by n-AlGaN inserted layer that contribute to separate and transport the photon-generated carriers. [ABSTRACT FROM AUTHOR]

The fabrication and characterization of GaN/Al0.1Ga0.9N visible-blind ultraviolet double heterojunction phototransistors (DHPTs), grown by low-pressure metal organic chemical vapor deposition on sapphire substrates were reported in this paper. The fabricated DHPTs with a 150-μm-diameter active area exhibited very low dark currents below 1pA up to a bias voltage of 3 V. High ultraviolet-to-visible rejection ratios of 1.9 × 104 and 1.2 × 102 were obtained at the bias voltages of 2 and 4 V, respectively. Optical gain as high as 1.6 × 103 was achieved. [ABSTRACT FROM AUTHOR]

AlN layers have been grown on 200 nm period of nanopatterned Si (111) substrates by cantilever epitaxy and compared with AlN layers grown by maskless lateral epitaxial overgrowth (LEO) on micropatterned Si (111) substrates. The material quality of 5-10 µm thick AlN grown by LEO is comparable to that of much thinner layers (2 µm) grown by cantilever epitaxy on the nanopatterned substrates. Indeed, the latter exhibited root mean square (RMS) roughness of 0.65 nm and X-ray diffraction full width at half-maximum (FWHM) of 710 arcsec along the (0002) reflection and 930 arcsec along the (10-15) reflection. The corresponding room temperature photoluminescence spectra was dominated by a sharp band edge peak. Back emission ultra violet light emitting diodes (UV LEDs) were fabricated by flip chip bonding to patterned AlN heat sinks followed by complete Si (111) substrate removal demonstrating a peak pulsed power of ∼0.7 mW at 344 nm peak emission wavelength. The demonstrated UV LEDs were fabricated on a cost effective epitaxial structure grown on the nanopatterned Si substrate with a total thickness of 3.3 µm. [ABSTRACT FROM AUTHOR]