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We demonstrate the growth of full-composition-graded InxGa1−xN (0 ≤ x ≤ 1) on a GaN/sapphire template using plasma-assisted molecular beam epitaxy. Composition of indium in InxGa1−xN films is controlled by growth temperature and gallium flux. It was found that In composition increases gradually from x = 0 (GaN) to x = 1 (InN) along the growth direction accompanied by a gradual strain relaxation. At the initial stage of growth, multiple quantum wells like structures with low and high In composition InxGa1−xN layers are spontaneously formed, effectively relaxing the in-plane strain. Finally, the graded InxGa1−xN film exhibits a broadband absorption covering the full solar spectrum, which provides a promising path for the design and production of graded InxGa1−xN based photovoltaic devices. [ABSTRACT FROM AUTHOR]

The effect of high temperature annealing (HTA) on crystalline quality improvement of h-BN films grown on sapphire substrates has been investigated. It is found that BN grown using conventional molecular beam epitaxy is disordered due to the growth temperature below 1000 °C. By annealing at a temperature of 1700 °C, thermodynamically stable crystalline h-BN could be obtained at wafer scale, where diffusion of atoms in the as-grown BN film is enhanced and the structural defect density decreases. The crystalline h-BN has been confirmed by x-ray diffraction, Raman scattering, and atomic force microscopy measurements. This work demonstrates that HTA is a simple and effective way to achieve wafer-scale crystalline h-BN films, which have numerous potential applications in next-generation two-dimensional devices and flexible III-nitride optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrated a top illuminated 1.55 μm metamorphic InGaAs resonant-cavity-enhanced p-i-n photodetector grown on GaAs substrate. The photodetectors were grown by a solid-source molecular beam epitaxy system. The high quality linearly graded InxAl0.4Ga1-x-0.4As metamorphic buffer layer enabled photodiodes to achieve ultralow dark current densities of 2.3×10-6 A/cm2 at 0 V and 4.2×10-5 A/cm2 at a reverse bias of 5 V. A high quantum efficiency of 84.4% at resonant wavelength of 1542 nm, a full width at half maximum about 14 nm, and a -3 dB bandwidth up to 13 GHz were also obtained. [ABSTRACT FROM AUTHOR]

The experimental data on band alignments of high-k Er2O3 films epitaxially grown on Si substrates by molecular beam epitaxy are reported. By using x-ray photoelectron spectroscopy, the valence and the conduction-band offsets of Er2O3 to Si are obtained to be 3.1±0.1 and 3.5±0.3 eV, respectively, showing a roughly symmetrical offset at the conduction and the valence band. The energy gap of Er2O3 is determined to be 7.6±0.3 eV. From the band offset viewpoint, those obtained numbers indicate that Er2O3 could be a promising candidate for high-k gate dielectrics. [ABSTRACT FROM AUTHOR]

Starting from the growth of high-quality 1.3 μm GaInNAs/GaAs quantum well (QW), the QW emission wavelength has been extended up to 1.55 μm by a combination of lowering growth rate, using GaNAs barriers and incorporating some amount of Sb. The photoluminescence properties of 1.5 μm range GaInNAsSb/GaNAs QWs are quite comparable to the 1.3 μm QWs, revealing positive effect of Sb on improving the optical quality of the QWs. A 1.59 μm lasing of a GaInNAsSb/GaNAs single-QW laser diode is obtained under continuous current injection at room temperature. The threshold current density is 2.6 kA/cm2 with as-cleaved facet mirrors. [ABSTRACT FROM AUTHOR]

We report the design, growth, fabrication, and characterization of a GaAs-based resonant-cavity-enhanced (RCE) GaInNAs photodetector operating at 1.55 μm. The structure of the device was designed using a transfer-matrix method (TMM). By optimizing the molecular-beam epitaxy growth conditions, six GaInNAs quantum wells were used as the absorption layers. Twenty-five (25)- and 9-pair GaAs/AlAs-distributed Bragg reflectors were grown as the bottom and top mirrors. At 1.55 μm, a quantum efficiency of 33% with a full width at half maximum of 10 nm was obtained. The dark current density was 3×10-7 A/cm2 at a bias of 0 V and 4.3×10-5 A/cm2 at a reverse bias of 5 V. The primary time response measurement shows that the device has a rise time of less than 800 ps. [ABSTRACT FROM AUTHOR]

InGaAsNSb/GaAs quantum wells (QWs) were grown by solid-source molecular-beam epitaxy using a N[sub 2] radio frequency plasma source. The effect of adding Sb during growth of InGaAsN/GaAs QWs was studied. X-ray diffraction, reflection high-energy electron diffraction and transmission electron microscopy studies indicate that Sb suppresses the three-dimensional growth and improves the interface of the QWs. X-ray diffraction and secondary ion mass spectroscopy analysis show that Sb gets incorporated into the quantum well, which becomes a quinternary compound that was previously unexplored. The introduction of Sb during growth of InGaAsN/GaAs QWs significantly enhances the optical properties of the QWs. 1.53 μm room-temperature photoluminescence was obtained from InGaAsNSb/GaAs QWs, which demonstrates the potential of fabricating 1.55 μm InGaAsNSb/GaAs QW lasers for long-haul applications. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

1.3 μm InGaAsN:Sb/GaAs multiple-quantum-well laser diodes have been grown by solid-source molecular-beam epitaxy using Sb as a surfactant. A low threshold of 1.1 kA/cm2 was achieved for broad-area laser diodes under pulsed operation at room temperature. High-temperature device characterization revealed characteristic temperatures (T[sub 0]) of 92 and 54 K for operating temperatures below and above 75 °C, respectively, as well as a lasing-wavelength temperature dependence of 0.36 nm/ °C. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]