We report on violet-emitting III-nitride light-emitting diodes (LEDs) grown bulk GaN substrates employing a flip-chip architecture. Device performance is optimized for operation at high current density and temperature, by specific design consideration the epitaxial layers, extraction efficiency, electrical injection. The power conversion efficiency reaches peak value of 84% 85 °C remains density, owing to low current-induced droop series resistance.

Carrier lifetime measurements reveal that, contrary to common expectations, the high-current non-radiative recombination (droop) in III-Nitride light emitters is comprised of two contributions which scale with cube carrier density: an intrinsic --most likely standard Auger scattering-- and extrinsic proportional density point defects. This second droop mechanism, hasn't previously been observed, caused by impurity-assisted process. Further, it shown that longer-wavelength suffer from higher...

The effects of NH3 flow, group III flux, and substrate growth temperature on indium incorporation surface morphology have been investigated for bulk InGaN films grown by ammonia molecular beam epitaxy. unintentional impurity elements (H, C, O) in was studied as a function polar (0001) GaN sapphire templates, nonpolar (101¯0) GaN, semipolar (112¯2), (202¯1) substrates. Enhanced observed both surfaces relative to c-plane, while reduced (112¯2) co-loaded conditions. Indium increase with...

The Current Aperture Vertical Electron Transistor (CAVET) combines the high conductivity of two dimensional electron gas channel at AlGaN/GaN heterojunction with better field distribution offered by a vertical design. In this work, CAVETs buried, conductive p-GaN layers as current blocking layer are reported. was regrown metalorganic chemical vapor deposition and subsequent regrowth done ammonia molecular beam epitaxy to maintain conductivity. Transistors ON (10.9 kA/cm2) low ON-resistance...

High external quantum efficiency (EQE) p-i-n heterojunction solar cells grown by NH3-based molecular beam epitaxy are presented. EQE values including optical losses greater than 50% with fill-factors over 72% when illuminated a 1 sun AM0 spectrum. Optical absorption measurements in conjunction indicate an internal 90% for the InGaN absorbing layer. By adjusting thickness of top p-type GaN window contact layer, it is shown that short-wavelength (<365 nm) limited minority carrier...

The current-voltage characteristic and ideality factor of III-Nitride quantum well light-emitting diodes (LEDs) grown on bulk GaN substrates are investigated. At operating temperature, these electrical properties exhibit a simple behavior. A model in which only active-region recombinations have contribution to the LED current is found account for experimental results. limit efficiency discussed based thermodynamic arguments, implications electroluminescent cooling examined.

The physical process driving low-current non-radiative recombinations in high-quality III-nitride quantum wells is investigated. Lifetime measurements reveal that these scale with the overlap of electron and hole wavefunctions show a weak temperature dependence, contrast to common empirical expectations for Shockley-Read-Hall recombinations. A model field-assisted multiphonon point defect recombination introduced shown quantitatively explain data. This study clarifies how LEDs can achieve...

A comprehensive analysis of forward and reverse current Ga-face GaN p-n junctions grown by NH3 molecular beam epitaxy (NH3-MBE) on metal organic chemical vapor deposition (MOCVD) GaN:Fe sapphire is presented. NH3-MBE has a great potential for growing low leakage vertical devices due to its nitrogen-rich growth. Diodes with the lowest n-doping n∼3.5×1017 cm−3 exhibit an extremely 2.6×10−7 A/cm2 at −40 V ideality factor 1.3, which lower than state-of-the-art MOCVD. An explanation difficulty...

Deep level defects in nonpolar m-plane GaN grown by ammonia-based molecular beam epitaxy were characterized using deep transient spectroscopy (DLTS) and optical (DLOS) compared with polar c-plane that was simultaneously the same growth run. Significant differences both levels present their concentrations observed upon comparison of orientations. DLTS revealed electron traps activation energies 0.14 eV, 0.20 0.66 eV material, ∼10−50 × higher than similar material. Likewise, DLOS measurements...

We report on the light extraction efficiency of III-Nitride violet light-emitting diodes with a volumetric flip-chip architecture. introduce an accurate optical model to account for extraction. fabricate series devices varying configurations and fit their measured performance our model. show importance second-order effects like photon recycling residual surface roughness data. conclude that reach 89%.

An all-optical measurement of differential carrier lifetimes is performed in a specially designed single-quantum-well structure. The reveals the complex carrier-dependence radiative and non-radiative recombinations, which directly manifest wavefunction-overlap field-screening effects. This analysis clarifies range applicability common ABC model its limitations.

A detailed study of the small-signal response III-Nitride quantum well (QW) light-emitting diodes is presented, in which electrical and optical responses are simultaneously measured. complete transport-recombination model introduced to account for measurements. This allows a proper evaluation recombination lifetime accurate quantification thermionic carrier escape from QW. Further, yet-unreported capture mechanism identified quantified; it increases with density QW bears signature Coulomb...

The hole concentration p in Mg-doped GaN films grown by ammonia molecular beam epitaxy depends strongly on the growth temperature TGR. At TGR=760 °C, GaN:Mg showed a of p=1.2 × 1018 cm−3 for [Mg]=4.5×1019 cm−3, while at TGR=840 p=4.4×1016 [Mg]=7×1019 cm−3. Post-growth annealing did not increase p. sample 760 °C exhibited low resistivity 0.7 Ωcm. mobility all samples was around 3−7 cm2/V s. Temperature-dependent Hall measurements and secondary ion mass spectroscopy suggest that TGR>760...

InAlN lattice-matched to GaN was grown by molecular beam epitaxy (MBE) using ammonia as the nitrogen source. The alloy composition, growth conditions, and strain coherence of were verified high resolution x-ray diffraction ω-2θ scans reciprocal space maps. Scanning transmission electron microscopy energy-dispersive spectroscopy revealed absence lateral composition modulation that observed in films plasma-assisted MBE. InAlN/AlN/GaN mobility transistors with smooth surfaces fabricated...

In this letter, we report on the interfacial abruptness of GaN/AlN/GaN heterostructures with pulsed laser atom probe tomography (APT). The samples were grown by plasma-assisted molecular beam epitaxy (MBE) under both metal-rich and N-rich conditions Ga-polar (0001) GaN templates N-polar (0001¯) substrates. An NH3 assisted MBE technique was involved to grow similar structures GaN:Fe substrates GaN/Al2O3 templates, respectively, for a comparison study. We find in all cases interface net...

Deep level transient spectroscopy (DLTS) and deep optical (DLOS) were utilized to investigate the behavior of states in m-plane, n-type GaN grown by ammonia-based molecular beam epitaxy (NH3-MBE) as a function systematically varied V/III growth flux ratios. Levels detected at EC − 0.14 eV, 0.21 0.26 0.62 0.67 2.65 3.31 with concentrations several traps exhibiting systematic dependencies on ratio. The DLTS spectra are dominated eV whose decreased monotonically increasing ratio decreasing...

A monolithic coupling scheme in which two active waveguides merge into a single waveguide is presented for GaAs∕AlGaAs quantum cascade laser. The evolving fields interfere and constant phase observed the Y-shaped laser cavity, resulting far field pattern of double slit. mode distribution comprehensively derived by matching profiles to simulated values shows weak current dependence. device demonstrates feasibility coherent resonators with prospective applications interferometric sensing high...

Midinfrared quantum cascade lasers with monolithically integrated Y-junctions are investigated. Two different emission wavelengths of 10.5 and 4.2μm were realized in two material systems, lattice-matched GaAs∕AlGaAs on GaAs strain-compensated InGaAs∕InAlAs∕AlAs InP. With identical Y-junction dimensions, phase locking is observed both structures. In based devices, fundamental lateral modes present the coupled waveguides, which coherently synchronized at Y-junction. InP higher order excited,...

It has been long recognized that the capacitance-voltage (C-V) profiling technique only yields an apparent carrier concentration n̂, which, in general, differs from majority concentration. However, it is still possible to extract conduction band offset ΔEc and interface charge σi provided doping profile exact hetero-interface position are known. We will show case of σi∼1012cm−2, which typical for polar III-nitrides, misplacement as small 1 nm leads a large error extracted ΔEc, making...

We demonstrate AlGaN/GaN heterojunction bipolar transistors (HBTs) by ammonia molecular beam epitaxy (NH3 MBE). The several benefits offered NH3 MBE for the growth of GaN based vertical electronic devices are discussed. To obtain good ohmic contacts to base layer, were fabricated with two different processes involving regrowths – regrown contact (Wafer A) and emitter B). Devices on Wafers A B had similar DC performance. Common (CE) operation a peak collector current density, JC > 1 kA/cm2...

Indium nitride is the least studied of III-nitride though it has great potential due to its small bandgap 0.65 eV and a effective electron mass. InN:Mg was recently confirmed be p-type. However, Hall measurements on still show n-type conductivity, even when very thick. Some studies have suggested possibility high coupling resistance between surface accumulation bulk p-InN. In this study, we through vertical transmission-line model measurement that should not affect conductivity measurements.

The reduced polarization of nonpolar and semipolar orientations the III-Nitrides is very attractive for optoelectronics applications. Several properties these have yet to be investigated. In particular, there no a priori reason band offset same different crystallographical orientations. present article, we report on extraction GaN/AlxGa1–xN conduction offsets through capacitance-voltage profiling m-plane (101¯0) (202¯1) We extracted ΔEc:ΔEv 50:50–60:40. measured non-zero hetero-interface...

Current Aperture Vertical Electron Transistors (CAVETs) benefit from the high electron mobility of 2-dimensional gas (2-DEG) in lateral direction and better field distribution vertical geometry. flows laterally 2-DEG at AlGaN/GaN heterojunction is directed vertically down to drain, through aperture (Fig.1). A current blocking layer (CBL) used define low resistance aperture. In this work, we use conductive Mg-doped MOCVD p-GaN as CBL, hence flow by a reverse biased p-n junction opposed using...