Despite the high density of threading dislocations generally found in (AlGaIn)N heterostructures, light emission efficiency such structures is exceptionally high. It has become common to attribute compositional fluctuations or even phase separation active GaInN quantum well region. The resulting localization charge carriers thought keep them from recombining nonradiatively at defects. Here, we show that random disorder not key but under suitable growth conditions hexagonal V-shaped pits...

The interplay between band gap renormalization and filling (Burstein-Moss effect) in n-type wurtzite GaN is investigated. For a wide range of electron concentrations up to $1.6\ifmmode\times\else\texttimes\fi{}{10}^{20}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ spectroscopic ellipsometry photoluminescence were used determine the dependence energy Fermi edge on density. dominating effect an density about...

InGaN quantum wells were grown by metal organic vapor-phase epitaxy on polar (0 0 0 1), nonpolar (1 0  0) and semipolar (1 0  2), (1 1  2), (1 0  1) as well (2 0  1) oriented GaN substrates. The room-temperature photoluminescence (PL) electroluminescence (EL) emission energies for different crystal orientations show large variations of up to 600 meV. following order the energy was found throughout entire range growth temperatures: < (1 1  2) = (0 0 0 1) (1 0  2). In differentiate between...

The performance characteristics of optically pumped laser heterostructures emitting in the UV-C spectral range between 272 and 279 nm are investigated. were grown by metal-organic vapor phase epitaxy on (0001) planar AlN/sapphire, epitaxially laterally overgrown (ELO) bulk AlN substrates with threading dislocation densities ranging from 2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> to 10...

We report on the performance of AlGaN-based deep ultraviolet light-emitting diodes (UV-LEDs) emitting at 265 nm grown stripe-patterned high-temperature annealed (HTA) epitaxially laterally overgrown (ELO) aluminium nitride (AlN)/sapphire templates. For this purpose, structural and electro-optical properties ultraviolet-c (UVC-LEDs) as-grown HTA planar AlN/sapphire as well ELO with without are investigated compared. Cathodoluminescence measurements reveal dark spot densities <mml:math...

Herein, the scope is to provide an overview on current status of AlN/sapphire templates for ultraviolet B (UVB) and C (UVC) light‐emitting diodes (LEDs) with focus work done previously. Furthermore, approaches improve properties such by combination high‐temperature annealing (HTA) patterned interfaces are discussed. While beneficial effect HTA demonstrated UVC LEDs, growth relaxed AlGaN buffer layers AlN a challenge. To achieve low dislocation density, applicability investigated.

AlN layers annealed at high temperatures offer low threading dislocation densities of mid 108 cm−2 and are therefore increasingly used as base in ultraviolet (UV) light emitting diode (LED) heterostructure growth. These LEDs, just like those grown on conventional metalorganic vapor phase epitaxy (MOVPE) templates, often suffer from long-wavelength parasitic luminescence. In this work, luminescence properties far-UVC LED heterostructures MOVPE-AlN/sapphire templates high-temperature...

The high quantum efficiency of light emission from GaInN/GaN wells despite the typically large defect density still lacks a quantitative explanation. From detailed analysis highly efficient samples we find that reduction radiative probability due to free exciton dissociation is dominant mechanism limiting efficiency. Random localization shown be only minor contribution. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We demonstrate quantitatively that the realization of high internal quantum efficiency more than 70% at room temperature in $\mathrm{Ga}\mathrm{In}\mathrm{N}∕\mathrm{Ga}\mathrm{N}$ well structures is possible with potential barriers, which are caused by V-shaped pit formation around threading dislocations. Localization charge carriers present samples, but its contribution to negligible. The emission and recombination characteristics deep pits studied detail. Due narrower wells smaller...

We have optimized the internal quantum efficiency (IQE) of GaInN∕GaN quantum-well (QW) structures. For an emission wavelength 460nm, a high IQE 73% was achieved. longer wavelength, calculations predict higher oscillator strength for thinner QWs but In content. observe improvement in almost 50% when reducing QW width from 2.7nmto1.8nm, and increasing content whole blue to green spectral region with IQE=40% at 525nm. The typical saturation output power current that occurs, particularly...

Abstract We have investigated the MOVPE growth of semipolar gallium nitride (GaN) films on (10 $ \bar 1 0) m‐plane sapphire substrates. Specular GaN with a RMS roughness × 10 μm 2 ) 15.2 nm were obtained and an arrowhead like structure aligned along [ 113] is prevailing. The orientation relationship was determined by XRD yielded (2 2) ‖ [0001] as well [000 ] . PL spectra exhibited near band edge emission accompanied strong basal plane stacking fault emission. In addition lower energy peaks...

For the realization and improvement of GaN-based optoelectronic devices (light emitting diodes laser diodes) from ultraviolet to red wavelength range GaInN quantum well structures with high internal efficiency are great importance. To determine parameters which affect efficiency, we have analyzed emission intensity varied electron hole wave function overlap by temperature excitation power dependent time-resolved photoluminescence. The confined Stark effect reduces photoluminescence for thick...

Abstract The most promising approach for GaN substrate fabrication on the base of HVPE consists in growth thick crystals and subsequent cutting these boules into slices followed by conventional surface preparation. This work focusses a boule process optimized to highest rate use commercially available vertical reactor from AIXTRON order develop technology high productivity enable low‐cost substrates. To this end, up thicknesses 6.3 mm have been grown 2 inch GaN‐on‐sapphire templates produced...

Herein, AlN growth by metalorganic vapor‐phase epitaxy on hole‐type nanopatterned sapphire substrates is investigated. Cracking occurs for an unexpectedly thin‐layer thickness, which associated to altered nucleation conditions caused the pattern. To overcome obstacle of cracking and at same time decrease threading dislocation density order magnitude, high‐temperature annealing (HTA) a 300 nm‐thick starting layer successfully introduced. By this method, 800 nm‐thick, fully coalesced...

The influence of compressive strain in high-quality AlN templates on the subsequent growth AlGaN-based device layers was investigated. showed ∼−0.29% and threading dislocation densities (TDDs) below 6.5 × 108 cm−2. By introducing high Si-doping MOVPE-grown AlN, relaxed while preserving low TDD. this method, TDD transferred from template to micron-thick n-Al0.63Ga0.37N. A 275 nm LED demonstrated with a ∼2.5 times power enhancement than same conventional under current injection. maximum...

Abstract Ga x In 1–x N/GaN single quantum well (QW) structures emitting in the range of 450 nm to 620 have been grown by MOVPE. Temperature and excitation power dependent photoluminescence (PL) was used determine internal efficiency (IQE) for these structures. For blue QWs high IQE values on order 60% were achieved. Due a reduced growth temperature, rate increased V/III ratio we obtained with good morphology content above 25%. Thinner showed clear improvement compared QW‐structures larger...

Abstract A comparison of different epilayer concepts to achieve high breakdown voltage AlGaN‐GaN HFETs is presented. double heterostructure with a low Al‐content Al 0.05 Ga 0.95 N back‐barrier as well carbon‐doped GaN buffer are investigated regard material and device properties. Material analysis reaffirms the incorporation carbon on nitrogen lattice site without creation extended defects or causing memory effects. It demonstrated that carrier trapping in using deep acceptors reduces...

AlGaN multiple quantum well lasers for optical pumping have been grown by metal-organic vapor phase epitaxy on high and low dislocation density AlN/sapphire templates. Lasers planar templates exhibited densities V-pit densities, but a smooth surface morphology leading to inefficient, laterally very homogeneous emission. Lasing was not observed when optically pumped with up 50 MW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ....

The influence of the n-AlGaN contact layer thickness and doping profile on efficiency, operating voltage lifetime 310 nm LEDs has been investigated. Increasing n-contact reduces operation increases emission power slightly. Optimizing n-doping yielded enhanced conductivity reduced with a simultaneous output enhancement LEDs. Lifetime measurements have shown that even though was lifetimes were not negatively affected. Room temperature photoluminescence indicates low concentration point defects...

In this work, we compare the defect structure in unintentionally doped and Si-doped AlN layers grown by metalorganic vapor phase epitaxy (MOVPE) on high-temperature annealed (HTA) sputtered templates sapphire substrates. Since HTA process leads to a reduction of in-plane lattice constant layers, further homoepitaxial overgrowth results compressively strained layers. With increasing MOVPE-AlN layer thickness, strain relaxation takes place mostly formation dislocation half-loops an irregular...

Gallium phosphide (GaP) is a III–V semiconductor with remarkable optoelectronic properties, and it has almost the same lattice constant as silicon (Si). However, to date, monolithic large-scale integration of GaP devices remains challenging. In this study, we present nanoheteroepitaxy approach using gas-source molecular-beam epitaxy for selective growth islands on Si nanotips, which were fabricated complementary metal–oxide (CMOS) technology 200 mm n-type Si(001) wafer. Our results show that...

The light emission efficiency of (AlGaIn)N heterostructures and light-emitting diodes is exceptionally high, despite the high density threading dislocations generally found in such structures. It has become common to attribute compositional fluctuations or even phase separation active GaInN quantum well region. resulting localization charge carriers thought keep them from recombining non-radiatively at defects. Here, we show that are mobile room temperature rather than localized under...

We analyzed emission intensity, quantum efficiency, and emitted light polarization of c-plane AlGaN AlInGaN layers (λ = 320–350 nm) by temperature dependent photoluminescence. Low indium content in structures causes a significant intensity increase change the light. Polarization changes from E ⊥ c to ‖ with increasing aluminum content. It switches back incorporation indium. The degree decreases temperature. This dependence can corrupt internal efficiency determination