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%

Ta-Ru-N diffusion barriers for high-temperature contacts to p-type SiC

Compressively strained Ge (s-Ge) quantum well (QW) FinFETs with Si 0.3 Ge 0.7 buffer are fabricated on 300mm bulk Si substrate with 20nm W Fin and 80nm fin pitch using sidewall image transfer (SIT) patterning process. We demonstrate (a) in-situ process flow for a tri-layer high-κ dielectric HfO 2 /Al 2 O 3 /GeO x gate stack achieving ultrathin EOT of 0.7nm with low D IT and low gate leakage; (b) 1.3% s-Ge FinFETs with Phosphorus doped Si 0.3 Ge 0.7 buffer on bulk Si substrate exhibiting peak μ h =700 cm2/V s , μ h =220 cm2/Vs at 1013 /cm2 hole density. The s-Ge FinFETs achieve the highest μ*C max of 3.1×10−4 F/Vs resulting in 5x higher I ON over unstrained Ge FinFETs.

Enhancement mode strained (1.3%) germanium quantum well FinFET (W Fin =20nm) with high mobility (μ Hole =700 cm 2 /Vs), low EOT (∼0.7nm) on bulk silicon substrate

Cross-sectional transmission electron microscopy was used to study annealed Ti/Al/Ti/Au and V/Al/V/Au ohmic contacts to as-received and plasma-etched n-Al058Ga042N The reaction depth of low-resistance V-based contacts to as-received n-Al058Ga042N is very limited, unlike previously reported 	Ti-based contacts to n-Al
 x
 Ga1−x
 N In the present study, the Ti/Al/Ti/Au contacts to as-received n-Al058Ga042N required much higher annealing temperatures than the V-based contacts and also exhibited deeper reactions on the␣order of 40 nm To achieve a low contact resistance on plasma-etched n-Al058Ga042N, different metal layer thicknesses and processing conditions were required The Ti- and V-based contacts to plasma-etched n-Al058Ga042N exhibited both similar contact resistances and limited reaction depths, along with the presence of an aluminum nitride layer at the metallization/semiconductor interface Metal channels penetrate the aluminum nitride layer connecting the top of the metallization to the n-Al058Ga042N The similarity in phase formation in the contacts to plasma-etched n-Al058Ga042N is likely the reason behind the similarity in specific contact resistances

Ti/Al/Ti/Au and V/Al/V/Au contacts to Plasma-etched n-Al0.58Ga0.42N.

Ohmic contacts to p- and n-type 4H-SiC using refractory alloyed W:Ni thin films were investigated. Transfer length measurement test structures to p-type 4H-SiC (NA = 3 × 1020 cm−3) revealed Ohmic contacts with specific contact resistances, ρc, of ~10−5 Ω cm2 after 0.5 h annealing in argon at temperatures of 1000 °C, 1100 °C, 1150 °C, and 1200 °C. Contacts fabricated on n-type 4H-SiC (ND = 2 × 1019 cm−3) by similar methods were shown to have similar specific contact resistance values after annealing, demonstrating simultaneous Ohmic contact formation for W:Ni alloys on 4H-SiC. The lowest ρc values were (7.3 ± 0.9) × 10−6 Ω cm2 for p-SiC and (6.8 ± 3.1) × 10−6 Ω cm2 for n-SiC after annealing at 1150 °C. X-ray diffraction shows a cubic tungsten–nickel–carbide phase in the Ohmic contacts after annealing as well as WC after higher temperatures. Auger electron spectroscopy depth profiles support the presence of metal carbide regions above a nickel and silicon-rich region near the interface. X-ray energy dispersive spectroscopy mapping showed tungsten-rich and nickel-rich regions after annealing at 1100 °C and above. W:Ni alloys show promise as simultaneous Ohmic contacts to p- and n-SiC, offering low and comparable ρc values along with the formation of WxNiyC.

http://iopscience.iop.org/article/10.1088/0268-1242/30/10/105019/pdf

Characterization of tungsten–nickel simultaneous Ohmic contacts to p- and n-type 4H-SiC

Successful application of the silicide-like NixInGaAs phase for self-aligned source/drain contacts requires the formation of low-resistance ohmic contacts between the phase and underlying InGaAs. We report Ni-based contacts to InP-capped and uncapped n+- In0.53Ga0.47As (ND = 3 × 1019 cm−3) with a specific contact resistance ( ρc) of 4.0 × 10−8 ± 7 × 10−9 Ω·cm2 and 4.6 × 10−8 ± 9 × 10−9 Ω·cm2, respectively, after annealing at 350 °C for 60 s. With an ammonium sulfide pre-metallization surface treatment, ρc is further reduced to 2.1 × 10−8 ± 2 × 10−9 Ω·cm2 and 1.8 × 10−8 ± 1 × 10−9 Ω·cm2 on epilayers with and without 10 nm InP caps, respectively. Transmission electron microscopy reveals that the ammonium sulfide surface treatment results in more complete elimination of the semiconductor's native oxide at the contact interface, which is responsible for a reduced contact resistance both before and after annealing.

Suzanne E. Mohney

Papers

Ta-Ru-N diffusion barriers for high-temperature contacts to p-type SiC

Enhancement mode strained (1.3%) germanium quantum well FinFET (W Fin =20nm) with high mobility (μ Hole =700 cm 2 /Vs), low EOT (∼0.7nm) on bulk silicon substrate

Ti/Al/Ti/Au and V/Al/V/Au contacts to Plasma-etched n-Al0.58Ga0.42N.

Characterization of tungsten–nickel simultaneous Ohmic contacts to p- and n-type 4H-SiC

Very low resistance alloyed Ni-based ohmic contacts to InP-capped and uncapped n+-In0.53 Ga0.47As