We report the realization of a new multi-band-gap semiconductor. The highly mismatched alloy Zn 1-y Mn y O x Te 1-x has been synthesized using the combination of oxygen ion implantation and pulsed laser melting. Incorporation of small quantities of isovalent oxygen leads to the formation of a narrow, oxygen-derived band of extended states located within the band gap of the Zn 1-y Mn y Te host. When only 1.3% of Te atoms is replaced with oxygen in a Zn 0.88 Mn 0.12 Te crystal (with band gap of 2.32 eV) the resulting band structure consists of two direct band gaps with interband transitions at ~1.77 eV and 2.7 eV. This remarkable modification of the band structure is well described by the band anticrossing model in which the interactions between the oxygenderived band and the conduction band are considered. With multiple band gaps that fall within the solar energy spectrum, Zn 1-y Mn y O x Te 1-x is a material perfectly satisfying the conditions for single-junction photovoltaics with the potential for power conversion efficiencies surpassing 50%.PACS numbers: 71.20.Nr; 78.66.Hf; 61.72.Vv; 89.30.Cc The unusual properties of HMAs are well explained by the recently developed band anticrossing (BAC) model [3][4][5]. The model has also predicted several new effects that were later confirmed by experiments [6][7][8]. According to this model the electronic structure of the HMAs is determined by the interaction between localized states associated with N or O atoms and the extended states of the host semiconductor matrix.As a result the conduction band splits into two subbands with distinctly non-parabolic dispersion relations [3].In most instances, e.g. N in GaAs or O in CdTe, the localized states are located within the conduction band and the anticrossing interaction results in the formation of a relatively wide lower subband [5]. The subband is shifted to lower energies leading to a reduction of the energy band gap. The BAC model predicts that a narrow band can be formed only if the localized states occur well below the conduction band edge. Such a case is realized in ZnTe, MnTe and Zn 1-y Mn y Te alloys where the O level is located roughly 0.2 eV below the conduction band edge.We have shown recently that pulsed laser melting (PLM) followed by rapid thermal annealing (RTA) is well suited for the synthesis of HMAs. The combined ion 3 beam and laser processing approach has been demonstrated as an effective approach to synthesize dilute semiconductor alloys including GaN x As 1-x [9,10] and Ga 1-x Mn x As [11].Large enhancement by a factor of five in the incorporation of N in N + -implanted GaAs was observed. This is attributed to the rapid recrystallization rate associated with this process which results in the incorporation of impurity atoms to a level well above the solubility limit [12,13].Here we report the design and synthesis of a new type of material, the highly semiconductor [20,21]. Even for this non-optimal band gap configuration we calculate a power conversion efficiency of 45%, which is higher than th...

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We report an energy gap for hole photoexcitation in ferromagnetic Ga 1-x Mn x P that is tunable by Mn concentration (x ≤ 0.06) and by compensation with Te donors. For x~0.06, electrical transport is dominated by excitation across this gap above the Curie temperature (T C ) of 65 K and by thermally-activated hopping below T C . Magnetization measurements reveal a moment of 3.5 µ B per substitutional Mn while the large anomalous Hall signal unambiguously demonstrates that the ferromagnetism is carriermediated. In aggregate these data indicate that ferromagnetic exchange is mediated by holes localized in a Mn-derived band that is detached from the valence band.

We have studied the effect of sodium on the electrical properties of Cu 2 ZnSnS 4 (CZTS) single crystal by using temperature dependence of Hall effect measurement. The sodium substitution on the cation site in CZTS is observed from the increasing of unit-cell size by powder X-ray diffraction. Sodium increases the effective hole concentration and makes the thermal activation energy smaller. The degree of compensation decreases with sodium incorporation, thus the hole mobility is enhanced. We revealed that sodium is important dopant in CZTS to control the electrical properties. V

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We demonstrate the formation of ferromagnetic Ga 1-x Mn x As films by Mn ion

We investigate the synthesis of kesterite Cu 2 ZnSnS 4 (CZTS) polycrystalline thin films using cosputtering from binary sulfide targets followed by annealing in sulfur vapor at 500°C to 650°C. The films are the kesterite CZTS phase as indicated by x-ray diffraction, Raman scattering, and optical absorption measurements. The films exhibit (112) fiber texture and preferred low-angle and R3 grain boundary populations which have been demonstrated to reduce recombination in Cu(In,Ga)Se 2 and CdTe films. The grain growth kinetics are investigated as functions of temperature and the addition of Na. Significantly, lateral grain sizes above 1 lm are demonstrated for samples grown on Na-free glass, demonstrating the feasibility for CZTS growth on substrates other than soda lime glass.

We present a concept for improving the efficiency of thin-film solar cells via scattering from dielectric particles. The particles are embedded directly within the semiconductor absorber material with sizes on the order of one wavelength. Importantly, this geometry is fully compatible with the use of an anti-reflective coating (ARC) to maximize light capture. The concept is demonstrated through finite-difference time domain (FDTD) simulations of spherical SiO(2) particles embedded within a 1.0 microm layer of crystalline silicon (c-Si) utilizing a 75 nm ARC of Si(3)N(4). Several geometries are presented, with gains in absorbed photon flux occurring in the red end of the spectrum where silicon absorption is weak. The total integrated absorption of incident photon flux across the visible AM-1.5 spectrum is on the order of 5-10% greater than the same geometry without any dielectric scatterers.