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%

Ni, Pd, and Au Ohmic contacts to p-Al0.45Ga0.55N have been examined. We have observed that annealing the contacts in excess of 800°C is required to minimize the contact resistivity. However, the Pd and Au contacts annealed in excess of 700°C, which showed much better transport properties than Ni contacts annealed at the same temperatures, suffered from a rapid photoinduced degradation of both the current-voltage characteristics of the contacts and of the sheet resistance of the p-Al0.45Ga0.55N itself. This degradation was greatly reduced by passivating the p-Al0.45Ga0.55N surface with a SiNx film. A hypothesis is presented to describe the observed degradation.

Ohmic contacts to p-type Al0.45Ga0.55N

Ordered intermetallic films have a favorable combination of properties such as high strength, metallic electrical conductivity, good oxidation and corrosion resistance, and a high melting temperature and thermal stability that make them suitable for microelectromechanical systems (MEMS). One potential drawback to intermetallics is a lack of ductility at room temperature; however, the B2 compounds NiAl and RuAl show some ductility at room temperature, which has been shown to increase as the grain size decreases. Additionally, the fracture toughness of both materials is higher than those of Si and SiGe. It is also possible to deposit these materials at temperatures that make them compatible with complementary metal oxide semiconductor processing. The authors have shown that by controlling the Ar pressure during cosputtering, NiAl and RuAl thin films can be deposited near room temperature with stresses ranging from compressive to tensile, possibly eliminating the need for annealing. This article examines Ni–...

Developing Ni–Al and Ru–Al intermetallic films for use in microelectromechanical systems

The relationship between the specific contact resistance of nonalloyed Pd∕W∕Au ohmic contacts to p-In0.25Ga0.75Sb and premetallization surface preparations is examined. The resistance of ohmic contacts is minimized when p-InGaSb is exposed briefly to a dilute (NH4)2S solution. This treatment minimizes the thickness of any residual oxide or sulfide layer on the semiconductor and avoids excessive etching of the semiconductor, which would make the contact less shallow. A specific contact resistance of 5.9×10−7Ωcm2 is achieved for a Pd∕W∕Au (2∕50∕145nm) contact that consumes no more than 5nm of InGaSb.

Sulfur passivation for shallow Pd∕W∕Au ohmic contacts to p-InGaSb

Films of CdSe(ZnS) colloidal nanocrystalline quantum dots (NQDs) were deposited on bare silicon, glass and polymer coated silicon using mist deposition. This effort is a part of an exploratory investigation in which this deposition technique is studied for the first time as a method to form semiconductor NQD films. The process parameters, including deposition time, solution concentration and electric field, were varied to change the thickness of the deposited film. Blanket films and films deposited through a shadow mask were created to investigate the method's ability to pattern films during the deposition process. The differences between these deposition modes in terms of film morphology were observed. Overall, the results show that mist deposition of quantum dots is a viable method for creating thin, patterned quantum dot films using colloidal solution as the precursor. It is concluded that this technique shows very good promise for quantum dot (light emitting diode, LED) fabrication.

https://iopscience.iop.org/article/10.1088/0268-1242/24/10/105024/pdf

Suzanne E. Mohney

Papers

Ohmic contacts to p-type Al0.45Ga0.55N

Developing Ni–Al and Ru–Al intermetallic films for use in microelectromechanical systems

Sulfur passivation for shallow Pd∕W∕Au ohmic contacts to p-InGaSb

Studies of mist deposition for the formation of quantum dot CdSe films

Thermally Stable ZrN/Zr/n-GaN Ohmic Contacts