Papers by Keyword: Graded Band Gap

Abstract: To characterize the properties of the as-grown Al_xGa_1-xN material for producing high property Al_xGa_1-xN photocathode in ultraviolet (UV) detection, the Ar⁺ sputtering and X-ray photoelectric spectroscopy (XPS) scan are performed. XPS spectra indicates that although processed with chemical solutions, Al_xGa_1-xN still contains large amount of carbon and oxide on the surface, which can be completely removed by Ar⁺ sputtering within few minutes. Ga3d and Al2p curves show that there are other compounds of Ga and Al on the surface but both become very concentrated when sputtering continues. The proportion of Al increases and that of Ga decreases gradually from surface to AlN bulk, which testify the graded band gap profile of the Al_xGa_1-xN sample. There is always a very slight amount of oxygen in the AlN layer, which is regarded as native element during material growth. At the interface of AlN and sapphire, an abrupt transition appears which can influence the properties of the Al_xGa_1-xN photocathode when it works with the transmittance mode

Abstract: The photo current-voltage characteristic of a solar cell with graded band gap is calculated numerically based on the drift-diffusion equation and Poisson equation. The calculated efficiency of the CdTe solar cell with p-n junction located in 1μm depth increases remarkably when the band gap of the front n-type layer is graded. The effect is strong for high surface recombination velocity and is remarkable even at: the calculated efficiency increases from 19.6% to 24.3%.

Abstract: The aim of this work is to study optical properties of Si nanohills formed on the SiO2/Si interface by the pulsed Nd:YAG laser radiation. Nanohills which are self-organized on the surface of Si, are characterized by strong photoluminescence in the visible range of spectra with long wing in the red part of spectra. This peculiarity is explained by Quantum confinement effect in nanohillsnanowires with graded diameter. We have found a new method for graded band gap semiconductor formation using an elementary semiconductor. Graded change of band gap arises due to Quantum confinement effect.