Novel quantum-dot light-emitting diodes based on all-inorganic perovskite CsPbX3 (X = Cl, Br, I) nanocrystals are reported. The well-dispersed, single-crystal quantum dots (QDs) exhibit high quantum yields, and tunable light emission wavelength. The demonstration of these novel perovskite QDs opens a new avenue toward designing optoelectronic devices, such as displays, photodetectors, solar cells, and lasers.

Quantum Dot Light-Emitting Diodes Based on Inorganic Perovskite Cesium Lead Halides (CsPbX3)

This Review article summarizes the key advantages of using quantum dots (QDs) as luminophores in light-emitting devices (LEDs) and outlines the operating mechanisms of four types of QD-LED. The key scientific and technological challenges facing QD-LED commercialization are identified, together with on-going strategies to overcome these challenges.

Emergence of colloidal quantum-dot light-emitting technologies

The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

Gan : processing, defects, and devices

Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics, solar blind UV photodetectors, solar cells, and sensors with capabilities beyond existing technologies due to its large bandgap. It is usually reported that there are five different polymorphs of Ga2O3, namely, the monoclinic (β-Ga2O3), rhombohedral (α), defective spinel (γ), cubic (δ), or orthorhombic (e) structures. Of these, the β-polymorph is the stable form under normal conditions and has been the most widely studied and utilized. Since melt growth techniques can be used to grow bulk crystals of β-GaO3, the cost of producing larger area, uniform substrates is potentially lower compared to the vapor growth techniques used to manufacture bulk crystals of GaN and SiC. The performance of technologically important high voltage rectifiers and enhancement-mode Metal-Oxide Field Effect Transistors benefit from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. However, the absence of clear demonstrations of p-type doping in Ga2O3, which may be a fundamental issue resulting from the band structure, makes it very difficult to simultaneously achieve low turn-on voltages and ultra-high breakdown. The purpose of this review is to summarize recent advances in the growth, processing, and device performance of the most widely studied polymorph, β-Ga2O3. The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed. Areas where continued development is needed to fully exploit the properties of Ga2O3 are identified.

A review of Ga2O3 materials, processing, and devices

Photocatalytic water splitting using semiconductors is attractive for converting solar energy into hydrogen. An efficient and scalable system based on particulate photocatalyst sheets is now shown to exhibit energy conversion efficiency exceeding 1%. Photocatalytic water splitting using particulate semiconductors is a potentially scalable and economically feasible technology for converting solar energy into hydrogen1,2,3. Z-scheme systems based on two-step photoexcitation of a hydrogen evolution photocatalyst (HEP) and an oxygen evolution photocatalyst (OEP) are suited to harvesting of sunlight because semiconductors with either water reduction or oxidation activity can be applied to the water splitting reaction4,5. However, it is challenging to achieve efficient transfer of electrons between HEP and OEP particles6,7. Here, we present photocatalyst sheets based on La- and Rh-codoped SrTiO3 (SrTiO3:La, Rh; ref. 8) and Mo-doped BiVO4 (BiVO4:Mo) powders embedded into a gold (Au) layer. Enhancement of the electron relay by annealing and suppression of undesirable reactions through surface modification allow pure water (pH 6.8) splitting with a solar-to-hydrogen energy conversion efficiency of 1.1% and an apparent quantum yield of over 30% at 419 nm. The photocatalyst sheet design enables efficient and scalable water splitting using particulate semiconductors.

Scalable water splitting on particulate photocatalyst sheets with a solar-to-hydrogen energy conversion efficiency exceeding 1%

Conformally coating textured, high surface area substrates with high quality semiconductors is challenging. Here, we show that a high pressure chemical vapor deposition process can be employed to conformally coat the individual fibers of several types of flexible fabrics (cotton, carbon, steel) with electronically or optoelectronically active materials. The high pressure (∼30 MPa) significantly increases the deposition rate at low temperatures. As a result, it becomes possible to deposit technologically important hydrogenated amorphous silicon (a-Si:H) from silane by a simple and very practical pyrolysis process without the use of plasma, photochemical, hot-wire, or other forms of activation. By confining gas phase reactions in microscale reactors, we show that the formation of undesired particles is inhibited within the microscale spaces between the individual wires in the fabric structures. Such a conformal coating approach enables the direct fabrication of hydrogenated amorphous silicon-based Schottky ...

Conformal coating of amorphous silicon and germanium by high pressure chemical vapor deposition for photovoltaic fabrics

Metal electrical contacts that exhibit good thermal stability and desirable electrical characteristics are required for the development of high temperature devices based on the III-V nitrides. To make improvements on existing contacts or to develop new ones, information on the metallurgy of these contacts is needed. In this work, selected early transition metal-based ohmic contacts to n-GaN are examined from both a high-temperature materials chemistry and electrical standpoint.

TiN and ZrN based ohmic contacts to n-GaN

A Pd/In/Pd/Pt/Au ohmic contact to n-GaSb is presented with a specific contact resistance of 2.4 × 10 −6 Ω cm 2 . The annealing temperature range over which the specific contact resistance drops to a minimum, while maintaining a suitable surface morphology, is at least twice that of previously reported ohmic contacts to n-GaSb. Materials characterization using cross-sectional transmission electron microscopy confirms that Ga x In 1− x Sb forms at the metal/semiconductor interface, and its formation is believed to be responsible for ohmic behavior.

An improved In-based ohmic contact to n-GaSb

Low-resistance V/Al/V/Ag contacts have recently been reported to Al0.27Ga0.73N/GaN heterostructures with a thin GaN cap. These contacts had smooth surfaces and good edge definition. In this study, the V/Al/V/Ag metallization was adapted to other compositions of n-AlxGa1−xN, and it was found to provide low specific contact resistances as well as smooth surfaces on both n-GaN and n-Al0.58Ga0.42N. Another advantage of these contacts is that limited changes in specific contact resistance and morphology were observed when changing the metal layer thicknesses and processing conditions of the V/Al/V/Ag metallization on these semiconductors. The V (20)/Al (95)/V (20)/Ag (120 nm) contact provided a specific contact resistance of (2.1±0.9)×10−6 Ω cm2 when annealed at 825 °C for 30 s on n-GaN and a V (20)/Al (95)/V (5)/Ag (120 nm) contact provided a value of (2.4±0.3)×10−4 Ω cm2 when annealed at 875 °C for 60 s on n-Al0.58Ga0.42N. In each case, transmission electron microscopy revealed that the reaction between the ...

Suzanne E. Mohney

Papers

Conformal coating of amorphous silicon and germanium by high pressure chemical vapor deposition for photovoltaic fabrics

TiN and ZrN based ohmic contacts to n-GaN

An improved In-based ohmic contact to n-GaSb

V/Al/V/Ag contacts to n-GaN and n-AlGaN

Room-temperature epitaxy of metal thin films on tungsten diselenide