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%

The authors describe a Pd/Ru/Au Ohmic contact with enhanced thermal stability over the more commonly used Pd/Pt/Au Ohmic contact for InAlSb/InAs high electron mobility transistors. Transmission electron microscopy shows that reaction between Pd and the semiconductor begins in samples even before they are annealed. Decreases in contact resistance are correlated with increasing reaction between Pd and the semiconductor for annealing and aging at 175–225 °C for 3 h or 1 week. Small voids form in severely aged samples but do not increase the contact resistance. The Ru diffusion barrier is never observed to react with any other materials in either the contact or the semiconductor, and Au remains isolated from the Pd-bearing reaction products and semiconductor.

Pd/Ru/Au Ohmic contacts to InAlSb/InAs heterostructures for high electron mobility transistors

Improved rhenium Schottky diodes to n-type gallium nitride

Phase equilibria in the M-In-P (M = transition metal) ternary systems is determined through a combination of thermodynamic calculation and experimentation. Palladium is identified as a particularly attractive metal for contacts to InP. One useful feature of this system for contact design is the occurance of Pd χ InP ternary phases. Additionally, Pdln is found to be in equilibrium with InP and is identified as a promising contact material to InP because of its high melting point, low resistivity, and favorable properties for processing. Progress in the development of Pdln-based contacts to InP is briefly discussed.

Metallurgical Behavior of the Metal-IN-P Systems: Implications for the Design of Contacts to Inp

Gold, palladium, platinum or nickel ohmic contacts on Mg doped p -type Al x Ga 1-x N with x = 0.4 and x = 0.45 have been examined. The Au contact provided the lowest contact resistivity with p c = 1.8 (± 1.1) x 10 −3 Ωcm 2 , but only following annealing at 850°C. For the Pd, Au, and Pt contacts annealed at greater than 700°C, a rapid degradation in the current-voltage curves was observed upon testing. The degradation was induced by exposure to sub-bandgap light and was reversed with a mild anneal at 500°C. Possible mechanisms for the degradation are discussed.

Contacts to High Aluminum Fraction p -type Aluminum Gallium Nitride

: This report describes the development of composite ohmic contact and packaging technologies for the wideband gap semiconductor silicon carbide (SiC) with demonstrations of these technologies using 4H-SiC JFETs (junction field effect transistors). The goal of this effort is protection against oxidation / inter-diffusion and stable operation in air at 350 degrees C for up to 10,000 hr. Ta-Si and Ru-Ta barrier layers have been developed and tested for composite contacts that consist of the ohmic contact layer (e.g., Ni2Si), the barrier layer, an adhesion layer such as Pt and a gold cap layer that is suitable for wire bonding. Reliability and failure analysis studies have been conducted for chip metallizations for die attachment and for large area wire bonding to substrate metals, die metals and die metals over SiO2. 1800V/5A 4H-SiC JEFETs have been designed and fabricated using the Ta-Si and Ru-Ta barrier layers in the composite ohmic contacts. The devices were characterized at 300 ?C and used in the design of a 2W, 270-28V dc-dc converter. With Vgate = -33V, the JFETs were able to block 600V with J < 32microamps/sq cm at 300 degrees C.

Contact Metallization and Packaging Technology Development for SiC Bipolar Junction Transistors, PiN Diodes, and Schottky Diodes Designed for Long-Term Operations at 350degreeC

Suzanne E. Mohney

Papers

Pd/Ru/Au Ohmic contacts to InAlSb/InAs heterostructures for high electron mobility transistors

Improved rhenium Schottky diodes to n-type gallium nitride

Metallurgical Behavior of the Metal-IN-P Systems: Implications for the Design of Contacts to Inp

Contacts to High Aluminum Fraction p -type Aluminum Gallium Nitride

Contact Metallization and Packaging Technology Development for SiC Bipolar Junction Transistors, PiN Diodes, and Schottky Diodes Designed for Long-Term Operations at 350degreeC