Single crystal AlN provides a native substrate for Al-rich AlGaN that is needed the development of efficient deep ultraviolet light emitting and laser diodes. An absorption band centered around 4.7 eV (∼265 nm) with an coefficient above 1000 cm−1 observed in these substrates. Based on density functional theory calculations, substitutional carbon nitrogen site introduces at this energy. A series single crystalline wafers were used to demonstrate linearly increased carbon, strongly supporting...

AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) were fabricated on AlN substrates. The substrates prepared by growing thick hydride vapor phase epitaxy (HVPE)-AlN layers bulk physical transport (PVT). After an LED structure, the PVT-AlN removed mechanical polishing. This process allowed fabrication of DUV-LEDs HVPE-AlN with high crystalline quality and DUV optical transparency. exhibited a single emission peaking at 268 nm through output power as 28 mW was obtained injection...

The structural and optical quality of a freestanding AlN substrate prepared from thick layer grown by hydride vapor phase epitaxy (HVPE) on bulk (0001)AlN physical transport (PVT) were investigated. HVPE-AlN was crack- stress-free. High-resolution X-ray diffraction ω-rocking curves symmetric (0002) skew-symmetric (1011) reflections had small full widths at half maximum (FWHMs) 31 32 arcsec, respectively. Deep-ultraviolet transparency the higher than that PVT-AlN substrate, which related to...

The reliability and output power of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) fabricated on AlN substrates prepared by hydride vapor phase epitaxy are reported. TEM analysis revealed that dislocation density in LED layers, except the p-GaN layer, was below 106 cm-2. DUV-LEDs emitting at 261 nm exhibited an 10.8 mW 150 mA. lifetime these LEDs estimated to be over 10,000 h for cw operation 50 No significant acceleration decay higher currents observed. current mA 5,000 h.

AlN and AlGaN epitaxial films were deposited by metal organic chemical vapor deposition on single crystal substrates processed from boules grown physical transport. Structural, chemical, optical characterization demonstrated the high crystalline quality of interfaces.

To unambiguously distinguish lasing from super luminescence, key elements of such as longitudinal cavity modes with narrow line-width, polarized emission, and elliptically shaped far-field pattern, need to be demonstrated at the same time. Here, we show transverse electric 280.8 nm 263.9 for AlGaN based multi-quantum-wells double heterojunction structures fabricated on single crystalline AlN substrates. An pattern was recorded when pumped above threshold. With cavities shorter than 200 μm,...

A prominent 2.8 eV emission peak is identified in bulk AlN substrates grown by physical vapor transport. This shown to be related the carbon concentration samples. Density functional theory calculations predict that this caused a donor-acceptor pair (DAP) recombination between substitutional on nitrogen site and vacancy. Photoluminescence photoluminescence-excitation spectroscopy are used confirm model indicate DAP character of emission. The interaction defects provides pathway creating...

Deep ultraviolet (UV) light-emitting diodes (LEDs) at a wavelength of 226 nm based on AlGaN/AlN multiple quantum wells using p-type Si as both the hole supplier and reflective layer are demonstrated. In addition to description transport mechanism that allows injection from into wide bandgap device, details LED structure which take advantage enhance light extraction efficiency (LEE) elaborated. Fabricated LEDs were characterized electrically optically. Owing efficient enhanced LEE...

AlGaN based 229 nm light emitting diodes (LEDs), employing p-type Si to significantly increase hole injection, were fabricated on single crystal bulk aluminum nitride (AlN) substrates. Nitride heterostructures epitaxially deposited by organometallic vapor phase epitaxy and inherit the low dislocation density of native substrate. Following epitaxy, a p-Si layer is bonded heterostructure. LEDs characterized both electrically optically. Owing defect films, large concentration holes from p-Si,...

Abstract Sub‐300 nm optically pumped ultraviolet lasers were realized on low‐defect‐density (0001) AlN substrates fabricated from single crystalline boules. The Al x Ga 1– N/Al y N hetero‐structures grown by metal‐organic vapor phase epitaxy near atmospheric pressure. high structural quality of the pseudomorphically deposited films was confirmed X‐ray reciprocal space mappings and time‐resolved photoluminescence (PL) studies multiple quantum well emission. initial PL‐decay times for a sample...

Co-doping AlN crystals with Si is found to suppress the unwanted 4.7 eV (265 nm) deep ultraviolet absorption associated isolated carbon acceptors common in materials grown by physical vapor transport. Density functional theory calculations hybrid functionals demonstrate that silicon forms a stable nearest-neighbor defect complex carbon. This predicted absorb at 5.5 and emit or above 4.3 eV. Absorption photoluminescence measurements of co-doped samples confirm presence CN-SiAl emission peaks...

We demonstrate large area (25 000 μm2) Al-rich AlGaN-based avalanche photodiodes (APDs) grown on single crystal AlN substrates operating with differential (the difference in photocurrent and dark current) signal gain of 100 at 90 pW (<1 μW cm−2) illumination very low currents <0.1 pA room temperature under ambient light. The high AlGaN APDs is attributed to a breakdown voltage 340 V, corresponding fields ∼9 MV cm−1 as consequence threading screw dislocation densities <...

The authors present optical and electrical data for long wavelength (573–601nm) InGaN∕GaN multiple quantum well light emitting diodes (LEDs) grown by metal organic chemical vapor deposition. These results are achieved optimizing the active layer growth temperature width. Also, p-GaN is at low to avoid disintegration of InGaN wells with high InN content. A redshift observed both green yellow LEDs upon decreasing injection current regime. In case LED, this shift enough push emission into amber (601nm).

Abstract We report a kV class, low ON-resistance, vertical GaN junction barrier Schottky (JBS) diode with selective-area p-regions formed via Mg implantation followed by high-temperature, ultra-high pressure (UHP) post-implantation activation anneal. The JBS has an ideality factor of 1.03, turn-on voltage 0.75 V, and specific differential ON-resistance 0.6 mΩ·cm 2 . breakdown the is 915 corresponding to maximum electric field 3.3 MV cm −1 These results underline that high-performance can be...

Record-low p-type resistivities of 9.7 and 37 Ω cm were achieved in Al0.7Ga0.3N Al0.8Ga0.2N films, respectively, grown on single-crystal AlN substrate by metalorganic chemical vapor deposition. A two-band conduction model was introduced to explain the anomalous thermal behavior resistivity Hall coefficient. Relatively heavy Mg doping (5 × 1019 cm−3), conjunction with compensation control, enabled formation an impurity band exhibiting a shallow activation energy ∼30 meV for wide temperature...

High p-conductivity (0.7 Ω−1 cm−1) was achieved in high-Al content AlGaN via Mg doping and compositional grading. A clear transition between the valence band impurity conduction mechanisms observed. The temperature depended strongly on gradient to some degree level. model is proposed explain role of polarization field enhancing conductivity Mg-doped graded films two types. This study offers a viable path technologically useful AlGaN.

Abstract The density and distribution of extended defects in AlN single crystals grown by physical vapor transport (PVT) was studied bright field polarized light microscopy, defect‐selective etching, high resolution X‐ray diffraction (HRXRD). Etch pits associated with dislocation arrays forming low angle grain boundaries (LAGB) were observed two types LAGB identified. Reduction under reduced radial temperature gradients, as estimated simulation the growth cell, demonstrated.

Understanding the band bending at interface of GaN/dielectric under different surface treatment conditions is critically important for device design, performance, and reliability. The effects ultraviolet/ozone (UV/O3) GaN on energy atomic-layer-deposition (ALD) Al2O3 coated Ga-polar were studied. UV/O3 post-ALD anneal can be used to effectively vary bending, valence offset, conduction dipole Al2O3/GaN interfaces. increases GaN, improves uniformity deposition, changes amount trapped charges...

Compositionally graded AlxGa1-xN epilayers were coherently grown on AlN single crystal substrates by MOCVD, and polarization-induced doping was determined contactless sheet resistance capacitance-voltage measurements unintentionally doped, n-type layers; temperature-dependent Hall effect a Mg p-type layer. The room-temperature resistivity, hole concentration, mobility of the layer from x= 1.0 to 0.36 1.2 Ωcm, 4.5x1018 cm-3, cm2/Vs, respectively, which represents significant improvement over...

Roles of Al-vacancy (VAl) complexes on the cathodoluminescence (CL) spectra Si-doped AlN grown by halide vapor phase epitaxy (HVPE) a physical-vapor-transported (0001) substrate are described, making connection with results positron annihilation measurements. A combination HVPE and enabled decreasing deleterious carbon concentration dislocation density, respectively, thus accentuating influences VAl-complexes luminescence processes. low-temperature CL spectrum unintentionally doped exhibited...

We report on the effects of piezoelectric field and well width transition energy intensity for InGaN quantum structures with GaN or AlInGaN quaternary barriers. It was found that emission compressively strained GaN/In0.08Ga0.92N wells exhibits a strong dependence not accounted by confinement subband shifting alone. However, unstrained layers barriers, no observed due to elimination field, which measured be at least 0.6 MV/cm wells. Furthermore, demonstrated higher than their counterparts all...

Using the physical vapor transport (PVT) method, single crystal boules of AlN have been grown and wafers sliced from them characterized by synchrotron white beam X-ray topography (SWBXT) in conjunction with optical microscopy. topographs reveal that contain dislocations are inhomogeneously distributed densities varying as low 0 cm -2 to high 10 4 . Two types identified: basal plane threading dislocations, both having Burgers vectors type 1/3<112-0> indicating their origin is likely due...

Aluminum nitride (AlN) single crystal boules were grown by physical vapor transport (PVT). Diameter expansion during boule growth, without the introduction of low angle grain boundaries (LAGB) around periphery, was confirmed crossed polarizer imaging, synchrotron white beam x-ray topography (SWBXT), and monochromatic (SMBXT). The densities basal plane dislocations (BPD) threading edge (TED) averaged from high-magnification topographs five regions a high-quality substrate 0 cm -2 992 ,...