RESUMO
It was recently shown that the kinetics of persistent photoconductivity (PPC) build-up in indium doped Cd(1-x)Mn(x)Te are non-exponential and can be described solely by the stretched-exponential function. The non-exponentiality is attributed to the indium related DX centers present in the materials. In order to explain this observation, low temperature photoconductivity build-up was studied for Cd(1-x)Mn(x)Te:In of two different manganese contents. It was found that this type of response has its origin in the heavy-tailed distribution of the DX centers. The distribution was analyzed in terms of photon flux. Increasing photon flux leads to the more dispersive behavior. It was also confirmed that the heavy-tailed distribution is due to the different local configuration of atoms surrounding DX centers in the alloy.
RESUMO
We report the realization of a new mult-band-gap semiconductor. Zn(1-y)Mn(y)OxTe1-x alloys have 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 are replaced with oxygen in a Zn0.88Mn0.12Te crystal the resulting band structure consists of two direct band gaps with interband transitions at approximately 1.77 and 2.7 eV. This remarkable modification of the band structure is well described by the band anticrossing model. With multiple band gaps that fall within the solar energy spectrum, Zn(1-y)Mn(y)OxTe1-x is a material perfectly satisfying the conditions for single-junction photovoltaics with the potential for power conversion efficiencies surpassing 50%.
RESUMO
Diffraction gratings have been encoded in bulk Cd(0.8)Zn(0.2)Te:In samples by near-band-gap excitation. The photoinduced index change is associated with persistent photoconductivity resulting from ionization of DX centers. The gratings have a thickness of 1.7 mm, as evinced by Bragg selectivity during the readout process. Encoded grating are shown to be persistent for sufficiently low temperatures and are not erased by subsequent writing of more gratings.
