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The authors propose a simple direct wet etching method to texture the indium-tin-oxide (ITO) p-contact layer of GaNbased light-emitting diodes (LEDs). It was found that high density ITO nanorods with average diameter of 140 nm and average height of 120 nm were formed after the LED samples were immersed in a solution consists of HCl (30%), FeCl3 (30%) and de-ionised water (40%) for 2 min at room temperature. It was also found that output power of the LEDs with 2 min direct wet etching was 21% higher than that of conventional LEDs. Furthermore, it was found that such enhancement should be attributed to the enhanced photon extraction from the front surface of the LED chip. [ABSTRACT FROM AUTHOR]

This study reports the development of GaN-based light-emitting diodes (LEDs) with Ni/Ag (1 nm±0.2 nm/ 100 nm±2 nm) layers underneath an insulating layer of SiO2. The results of this study confirm the thermal stability of a Ni/ Ag mirror with reflectance of 90.6±1.5% following thermal annealing at 500°C for 5 min. This approach achieves far superior current spreading and prevents the absorption of light through the use of an opaque p-pad electrode. With 20-mA current injection, the output power of the LED with SiO2/Ni/Ag layers was 6.5 and 12.1% greater than that of LEDs with and without a SiO2 layer, respectively. Furthermore, the 20-mA forward voltage increased only slightly from 3.03±0.01 to 3.05±0.01 V for LEDs with SiO2/Ni/Ag layers. Good reliability is also achieved for LEDs with SiO2/Ni/Ag layers. [ABSTRACT FROM AUTHOR]

The growth of quaternary AlInGaN epitaxial layer on GaN/sapphire substrates by metalorganic chemical vapour deposition is reported. It was found that AlInGaN layers were grown three dimensionally with rough surface at low temperatures and transferred to smooth two-dimensional growth at 860°C. It was also found that In mole fraction in the layers decreased significantly as the AlInGaN growth temperature was increased while Al composition ratio was much less temperature dependent. Furthermore, it was found that solar-blind metal-insulator-semiconductor photodetectors with AlInGaN layer prepared at 860°C could provide us a photocurrent-to-dark-current contrast ratio of 1.93×104 and a UV-to-visible rejection ratio of 38.0. [ABSTRACT FROM AUTHOR]

ZnO epitaxial films were grown on sapphire (0001) substrates by using rf plasma-assisted molecular beam epitaxy. Metal–semiconductor–metal (MSM) photodetectors with Iridium (Ir) electrodes were then fabricated. It was found that Schottky barrier heights at the non-annealed and 500°C-annealed Ir/ZnO interfaces were around 0.65 and 0.78 eV, respectively. With an incident wavelength of 370 nm and 1 V applied bias, it was found that the maximum responsivities for the Ir/ZnO/Ir MSM photodetectors with and without thermal annealing were 0.18 and 0.13 A/W, respectively. From transient response measurement, it was found that time constant τ of the fabricated photodetectors was 22 ms. For a given bandwidth of 100 Hz and 1 V applied bias, we found that noise equivalent power and corresponding detectivity D* were 6×10-13 W and 1.18×1012 cm Hz0.5/W, respectively. [ABSTRACT FROM AUTHOR]

Nitride-based high power flip-chip near-ultraviolet (UV) light emitting diodes (LEDs) with a reflective mirror are fabricated by depositing Al onto a Si submount. It is demonstrated that the Al layer coated onto a Si submount can effectively reflect downward emitting photons for flip-chip LEDs. Although the operation voltage of the proposed LEDs is slightly increased, it is found that the output power is at least 30% higher than that of conventional LEDs. It is also found that flip-chip near-UV LEDs are more reliable than conventional non-flip-chip LEDs. [ABSTRACT FROM AUTHOR]

Thin InGaN epitaxial layers and GaN-based light-emitting diodes (LEDs) on conventional and vicinal cut sapphire substrates are prepared. It is found that indium atoms are distributed much more uniformly in the samples prepared on vicinal cut sapphire substrates. It is also found that stronger electroluminescence intensity can be achieved without the band-filling effect of localised states from the LEDs with vicinal cut sapphire substrate. With 20 mA current injection, it is found that 44% electroluminescence intensity enhancement can be achieved by using the 1° tilted sapphire substrate. [ABSTRACT FROM AUTHOR]

GaN-based metal-insulator-semiconductor (MIS) two-dimensional electron gas ultraviolet (UV) photodetectors with sputtered SiO2 insulation and passivation layers were fabricated. With a 5 V applied bias and 35 mW deuterium lamp irradiation, it was found that the photocurrent to dark current contrast ratio was 2.1×104 for the MIS photodetector with passivation. It was also found that UV to visible rejection ratio of such MIS photodetector with passivation was more than three orders of magnitude, while the responsivity was 0.144 A/W with a 5 V applied bias and a 350 nm incident light wavelength. Such a result was found to be much larger than those observed from the metal-semiconductor-metal photodetector and the MIS photodetector without passivation. [ABSTRACT FROM AUTHOR]

GaN-based indium‐tin-oxide (ITO) light emitting diodes (LEDs) with p-GaN, n+-short period superlattice (SPS) and nanostructured silicon contact layers were fabricated. It was found that surface of the ITO LED with nanostructured silicon layer was very rough. It was also found that 20 mA forward voltages measured from ITO LEDs with p-GaN, n+-SPS and nanostructured silicon contact layers were 6.01, 3.25 and 3.26 V, respectively. Compared with ITO LED with n+-SPS, it was found that output power of ITO LED with nanostructured silicon contact was 17% larger. Furthermore, it was found that ITO LED with nanostructured silicon contact was more reliable. [ABSTRACT FROM AUTHOR]

ZnSe-based white light emitting diodes (LEDs) were homoepitaxially prepared on ZnSe substrates by molecular beam epitaxy. It was found to be possible to simultaneously observe the greenish-blue emission at 483 nm originating from the epitaxial layer and the weaker ZnSe substrate-related orange emission centred at around 595 nm. It was found that the emission wavelength of the LED and the measured chromaticity coordinate were almost independent of the injected current. It was also found that the turn-on voltage and the 20 mA operation voltage of the fabricated LED were 2.25 and 4 V, respectively. [ABSTRACT FROM AUTHOR]