In this study, a full-potential density functional theory was used to investigate the effects of Ti substitution by different cations. In both rutile and anatase, Ti atom was replaced by Ce, Au, Sn, Ag, Mo, Nb, Zr, and Y. Phase stability, electronic structure and formation energy of oxygen vacancy were compared for rutile and anatase. The results indicated that substitution of Ce and Zr increas...

The maximum theoretical open circuit voltage of a solar cell is set by its builtin voltage. For amorphous silicon p-i-n cells, the position of the Fermi levels in the p-and ncontact regions are on the order of 0.4 eV and 0.2eV from their respective band edges, limiting the built-in voltage to Eg 0.6eV. We propose replacing the pand n regions by superlattices, in which the Fermi levels in the wi...

Core-level and valence band spectra of In x Ga1-x N films were measured using hard x-ray photoemission spectroscopy (HX-PES). Fine structure, caused by the coupling of the localized Ga 3d and In 4d with N 2s states, was experimentally observed in the films. Because of the large detection depth of HX-PES (∼20 nm), the spectra contain both surface and bulk information due to the surface band bend...

We calculate the {\em exact} time-resolved ARPES spectrum of a two-band model semiconductor driven out equilibrium by resonant and nonresonant laser pulses, highlighting effects phonon-induced decoherence relaxation. Resonant} excitations initially yield replica valence} band shifted upward energy exciton peak in photoabsorption. This phase is eventually destroyed decoherence: valence-band lowe...

The Fermi level position in (Ga,Mn)N has been determined from the period-analysis of GaN-related Franz-Keldysh oscillation obtained by contactless electroreflectance in a series of carefully prepared by molecular beam epitaxy GaN/Ga1-xMnxN/GaN(template) bilayers of various Mn concentration x. It is shown that the Fermi level in (Ga,Mn)N is strongly pinned in the middle of the band gap and the t...

We report, for the first time, about an intermediate band solar cell implemented with InAs/AlGaAs quantum dots whose photoresponse expands from 250 to ∼6000  nm. To our knowledge, this is the broadest quantum efficiency reported to date for a solar cell and demonstrates that the intermediate band solar cell is capable of producing photocurrent when illuminated with photons whose energy equals t...

We present a combined theoretical and experimental study of the anisotropy in the optical absorption of V-shaped quantum wires. By means of realistic band structure calculations for these structures, we show that detailed information on the heavy-and light-hole states can be singled out from the anisotropy spectra independently of the electron confinement, thus allowing accurate valence band sp...

We report the observation of a sharp band-edge response in spectrally resolved differential reflectivity experiments on GaMnAs, in contrast to linear optical experiments in which large band-tail effects are known to dominate. The differential reflectivity response exhibits a blue shift relative to results in GaAs and LT-GaAs, consistent with the valence-band model of ferromagnetism. Our results...

Nanowire band-to-band tunneling field-effect transistors ͑TFETs͒ are simulated using the Wentzel– Kramers–Brillouin ͑WKB͒ approximation and an atomistic, full-band quantum transport solver including direct and phonon-assisted tunneling ͑PAT͒. It is found that the WKB approximation properly works if one single imaginary path connecting the valence band ͑VB͒ and the conduction band ͑CB͒ dominates the tunne...

Scanning tunneling microscopy and spectroscopy are used to study InGaP/GaAs heterojunctions with InGaAs-like interfaces. Band offsets are probed using conductance spectra, with tip-induced band bending accounted for using 3-dimensional electrostatic potential simulations together with a planar computation of the tunnel current. Curve fitting of theory to experiment is performed. Using an InGaP ...