Preface. Contents of volumes 1-6. 1. Magnetism in ultrathin transition metal films (U. Gradmann). 2. Energy band theory of metallic magnetism in the elements (V.L. Moruzzi, P.M. Marcus). 3. Density functional theory of the ground state magnetic properties of rare earths and actinides (M.S.S. Brooks, B. Johansson). 4. Diluted magnetic semiconductors (J. Kossut, W. Dobrowolski). 5. Magnetic properties of binary rare-earth 3d-transition-metal intermetallic compounds (J.J.M. Franse, R.J. Radwanski). 6. Neutron scattering on heavy fermion and valence fluctuation 4f-systems (M. Loewenhaupt, K.H. Fischer). Author index. Subject index. Materials index.

Handbook of Magnetic Materials

Ultraviolet (UV) radiation has a variety of impacts including the health of humans, the production of crops, and the lifetime of buildings. Based on the photovoltaic effect, self-powered UV photode...

Self-Powered Ultraviolet Photodetector with Superhigh Photoresponsivity (3.05 A/W) Based on the GaN/Sn:Ga2O3 pn Junction.

Over 9% Efficient Kesterite Cu2ZnSnS4 Solar Cell Fabricated by Using Zn1–xCdxS Buffer Layer

Heterojunctions have attracted considerable attention for efficiently utilizing solar energy and improving conversion efficiency during pollutant degradation. Herein, carbon nitride and hematite (α-Fe2O3) are used to prepare a Z-scheme 2D/2D α-Fe2O3/g-C3N4 heterojunction using an impregnation-hydrothermal method. The unique 2D/2D structure has a high interfacial area and widely-dispersed active sites. The energy band structure of the Z-scheme heterojunction leads to broad visible-light absorption and promotes charge transfer. Optimizing the content of the α-Fe2O3 precursor in composite leads to a maximum efficiency of 60.8% for the removal of 600 ppb of NO, which is approximately 1.78 times that of g-C3N4 (34.2%). The photocatalytic performance is greatly promoted because of the formation of the heterojunction and the strong interfacial action between g-C3N4 nanosheets and α-Fe2O3 nanoplates. Cycling experiments verify that the α-Fe2O3/g-C3N4 heterojunction has good stability and reusability. The α-Fe2O3/g-C3N4 heterojunction therefore has great potential in sustainable and efficient pollutant degradation.

Z-Scheme 2D/2D α-Fe2O3/g-C3N4 heterojunction for photocatalytic oxidation of nitric oxide

Doping problems in GaN and in AlGaN alloys are addressed on the basis of state-of-the-art first-principles calculations. For n-type doping we find that nitrogen vacancies are too high in energy to be incorporated during growth, but silicon and oxygen readily form donors. The properties of oxygen, including DX-center formation, support it as the main cause of unintentional n-type conductivity. For p-type doping we find that the solubility of Mg is the main factor limiting the hole concentration in GaN. We discuss the beneficial effects of hydrogen during acceptor doping. Compensation of acceptors by nitrogen vacancies may occur, becoming increasingly severe as x increases in Al_x Ga_(1-x)N alloys.

https://arxiv.org/pdf/cond-mat/9810385.pdf

Theory of Doping and Defects in III-V Nitrides

Magnesium ion implantation has been performed on a GaN substrate, whose surface has a high thermal stability, thus allowing postimplantation annealing without the use of a protective layer. The current–voltage characteristics of p–n diodes fabricated on GaN showed distinct rectification at a turn-on voltage of about 3 V, although the leakage current varied widely among the diodes. Coimplantation with magnesium and hydrogen ions effectively suppressed the leakage currents and device-to-device variations. In addition, an electroluminescence band was observed at wavelengths shorter than 450 nm for these diodes. These results provide strong evidence that implanted magnesium ions create acceptors in GaN.

https://iopscience.iop.org/article/10.7567/APEX.10.016501/pdf

P-type doping of GaN(000\bar{1}) by magnesium ion implantation

We have determined the schematic phase diagram in detail with high reliability for Fe silicides grown by solid phase epitaxy (SPE) on a $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ surface at wide Fe coverage $(0.2--56\phantom{\rule{0.3em}{0ex}}\mathrm{monolayers})$ and subsequent annealing temperatures from 300 to $800\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. In the SPE growth, $\ensuremath{\delta}\text{\ensuremath{-}}7\ifmmode\times\else\texttimes\fi{}7$, $1\ifmmode\times\else\texttimes\fi{}1$, $\mathrm{bcc}\text{\ensuremath{-}}\mathrm{Fe}(111)1\ifmmode\times\else\texttimes\fi{}1$, $2\ifmmode\times\else\texttimes\fi{}2$, $c(8\ifmmode\times\else\texttimes\fi{}4)$, $3\mathrm{D}\text{\ensuremath{-}}2\ifmmode\times\else\texttimes\fi{}2$ $(\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{FeSi}}_{2})$, $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}\text{\ensuremath{-}}R30\ifmmode^\circ\else\textdegree\fi{}$, $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{FeSi}}_{2}$, and fine polycrystalline phases are formed on the $\mathrm{Si}(111)$ surface depending on Fe coverage and annealing temperature. We have characterized the surface periodic structures and morphologies of all the above Fe silicide phases using low-energy electron diffraction and scanning tunneling microscopy. Reflection high-energy electron diffraction also has been used to determine three-dimensional structures. Based on the overall view regarding the formations and changes of Fe silicide phases on a $\mathrm{Si}(111)$ surface, we discuss the growth mechanisms.

Iron silicides grown by solid phase epitaxy on a Si(111) surface: Schematic phase diagram

We directly and non-destructively measured the valence band offset at the interface between CdS and Cu2ZnSnS4 (CZTS) using hard X-ray photoelectron spectroscopy (HAXPES), which can measure the electron state of the buried interface because of its large analysis depth. These measurements were made using the following real devices; CZTS(t = 700 nm), CdS(t = 100 nm)/CZTS(t = 700 nm), and CdS(t = 5 nm)/CZTS(t = 700 nm) films formed on Mo coated glass. The valence band spectra were measured by HAXPES using an X-ray photon energy of 8 keV. The value of the valence band offset at the interface between CdS and CZTS was estimated as 1.0 eV by fitting the spectra. The conduction band offset could be deduced as 0.0 eV from the obtained valence band offset and the band gap energies of CdS and CZTS.

Direct measurement of band offset at the interface between CdS and Cu2ZnSnS4 using hard X-ray photoelectron spectroscopy

The fabrication processes of p-type regions for vertical GaN power devices are investigated. A p-type body layer in a trench gate metal-oxide-semiconductor field-effect transistor requires precise control of the effective acceptor concentration, which is equal to the difference between the Mg acceptor concentration (Na) and the compensating donor concentration (Nd). The carbon atoms incorporated during growth via metalorganic vapor phase epitaxy substitute nitrogen sites (CN) and function as donor sources in a p-type GaN layer. Since interstitial H atoms ( H i ) also compensate holes, their removal from an Mg-doped layer is crucial. Extended anneals to release H atoms cause the formation of extra hole traps. The p+ capping layer allows effective and rapid removal of H atoms from a p-type body layer owing to the electric field across the p+/p– junction. On the other hand, selective area p-type doping via Mg ion implantation is needed to control the electrical field distribution at the device edge. Ultrahigh-pressure annealing (UHPA) under a nitrogen pressure of 1 GPa enables post-implantation annealing up to 1753 K without thermal decomposition. Cathodoluminescence spectra and Hall-effect measurements suggest that the acceptor activation ratio improves dramatically by annealing above 1673 K as compared to annealing at up to 1573 K. High-temperature UHPA also induces Mg atom diffusion. We demonstrate that vacancy diffusion and the introduction of H atoms from the UHPA ambient play a key role in the redistribution of Mg atoms.

Progress on and challenges of p-type formation for GaN power devices

https://iopscience.iop.org/article/10.7567/1347-4065/ab4610/pdf

Keita Kataoka

Papers

P-type doping of GaN(000\bar{1}) by magnesium ion implantation

Iron silicides grown by solid phase epitaxy on a Si(111) surface: Schematic phase diagram

Direct measurement of band offset at the interface between CdS and Cu2ZnSnS4 using hard X-ray photoelectron spectroscopy

Progress on and challenges of p-type formation for GaN power devices

Overview of carrier compensation in GaN layers grown by MOVPE: toward the application of vertical power devices