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We compare the optical properties and device performance of unpackaged InGaN/GaN multiplequantum-well light-emitting diodes (LEDs) emitting at ~430 nm grown simultaneously on a high-cost small-size bulk semipolar (112 2) GaN substrate (Bulk-GaN) and a low-cost large-size (1122) GaN template created on patterned (1012) r-plane sapphire substrate (PSS-GaN). The Bulk-GaN substrate has the threading dislocation density (TDD) of ~105 cm-2-106cm-2 and basal-plane stacking fault (BSF) density of 0 cm-1, while the PSS-GaN substrate has the TDD of ~2 x 108 cm-2 and BSF density of ~1 x 10³ cm-1. Despite an enhanced light extraction efficiency, the LED grown on PSS-GaN has two-times lower internal quantum efficiency than the LED grown on Bulk-GaN as determined by photoluminescence measurements. The LED grown on PSS-GaN substrate also has about two-times lower output power compared to the LED grown on Bulk-GaN substrate. This lower output power was attributed to the higher TDD and BSF density. [ABSTRACT FROM AUTHOR]

With a view to supporting the development of ultra-violet light-emitting diodes and related devices, the compositional, emission and morphology properties of Si-doped n-type AlxGa1-xN alloys are extensively compared. This study has been designed to determine how the different AlxGa1-xN crystal orientations (polar (0001) and semipolar (11–22)) affect group-III composition and Si incorporation. Wavelength dispersive x-ray (WDX) spectroscopy was used to determine the AlN mole fraction (x ≈ 0.57–0.85) and dopant concentration (3 × 1018–1 × 1019 cm−3) in various series of AlxGa1-xN layers grown on (0001) and (11–22) AlN/sapphire templates by metalorganic chemical vapor deposition. The polar samples exhibit hexagonal surface features with Ga-rich boundaries confirmed by WDX mapping. Surface morphology was examined by atomic force microscopy for samples grown with different disilane flow rates and the semipolar samples were shown to have smoother surfaces than their polar counterparts, with an approximate 15% reduction in roughness. Optical characterization using cathodoluminescence (CL) spectroscopy allowed analysis of near-band edge emission in the range 4.0–5.4 eV as well as various deep impurity transition peaks in the range 2.7–4.8 eV. The combination of spatially-resolved characterization techniques, including CL and WDX, has provided detailed information on how the crystal growth direction affects the alloy and dopant concentrations. [ABSTRACT FROM AUTHOR]

InxGa1−xN/GaN multiple quantum well structures (x = 0.13 and 0.18) embedded into p–i–n diodes on (20 2 ¯ 1 ¯ ) and (20 2 ¯ 1) oriented GaN substrates were investigated by electroreflectance, photocurrent, and electroluminescence. Transition energies in absorption and emission experiments were measured as a function of the polarization orientation of light and applied bias voltage. The results were analyzed by a perturbation theoretical model to determine polarization fields. For the (20 2 ¯ 1 ¯ ) sample (x = 0.18), the flatband voltage is found at + 1 V corresponding to a polarization field of − 458 kV / cm. For the (20 2 ¯ 1) sample (x = 0.13), the polarization field is estimated to be ≈ + 330 kV / cm at flatband voltage higher than turn-on voltage of this light emitting diode. [ABSTRACT FROM AUTHOR]

Abstractauthoren InGaN multiple quantum well light-emitting diodes (LEDs) were grown on chemically-mechanically polished (11 [ABSTRACT FROM AUTHOR]