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Using depletion approximation theory and introducing acceptor defects which can characterize radiation induced deep-level defects in AlGaN/GaN heterostructures, we set up a radiation damage model of AlGaN/GaN high electron mobility transistor (HEMT) to separately simulate the effects of several main radiation damage mechanisms and the complete radiation damage effect simultaneously considering the degradation in mobility. Our calculated results, consistent with the experimental results, indicate that thin AlGaN barrier layer, high Al content and high doping concentration are favourable for restraining the shifts of threshold voltage in the AlGaN/GaN HEMT; when the acceptor concentration induced is less than 1014cm[?]3, the shifts in threshold voltage are not obvious; only when the acceptor concentration induced is higher than 1016cm[?]3, will the shifts of threshold voltage remarkably increase; the increase of threshold voltage, resulting from radiation induced acceptor, mainly contributes to the degradation in drain saturation current of the current-voltage (I-V) characteristic, but has no effect on the transconductance in the saturation area. [ABSTRACT FROM AUTHOR]

Fluorozirconate glass containing Eu3+ ions and chloride ions are prepared by a meltquenching method. The luminescence behavior of Eu3+ affected by Cl ions is investigated. With increasing Cl ion concentration, the luminous intensity of Eu3+ is significantly enhanced and the quantum efficiency of fluorozirconate glass is improved. Meanwhile, the intensity parameter Ω2 increases according to the Judd–Ofelt calculation, which indicates the decrease of local symmetry. The average lifetime of Eu3+ increases by introducing the Cl ions. Moreover, we find two kinds of sites for Eu3+ ions in a glass network by analyzing the fluorescence decay. The distribution of Eu3+ ions changes with increasing Cl ion concentration. In addition, the excessive Cl ions lead to the separation of the glass phase and the formation of the crystal phase, thus reducing the transmittance dramatically. [ABSTRACT FROM AUTHOR]

We synthesize Tm3+/Tb3+/Eu3+ triply-doped ZrF4—BaF2—LaF3—AlF3—NaF (ZBLAN) transparent glass by using a melt-quenching method. Under excitation of 365 nm, the white emission with Commission internationale deL'Eclairage (CIE) coordinates of (0.33, 0.33) is achieved at the Eu3+ concentration of 1.1 mol%. The mechanisms for white emission and the energy transfer process of Tb3+ → Eu3+ are discussed in terms of the photoluminescence, photoluminescence excitation spectra, and the light emission decay curves. The nature for the Tb3+ → Eu3+ energy transfer is described with the aid of an energy level diagram. [ABSTRACT FROM AUTHOR]

By using temperature-dependent Hall, variable-frequency capacitance--voltage and cathodoluminescence (CL) measurements, the identification of inductively coupled plasma (ICP)-induced defect states around the AlxGa1-xN/GaN heterointerface and their elimination by subsequent annealing in AlxGa1-xN/GaN heterostructures are systematically investigated. The energy levels of interface states with activation energies in a range from 0.211 to 0.253 eV below the conduction band of GaN are observed. The interface state density after the ICP-etching process is as high as 2.75x1012 cm-2*eV-1. The ICP-induced interface states could be reduced by two orders of magnitude by subsequent annealing in N2 ambient. The CL studies indicate that the ICP-induced defects should be Ga-vacancy related. [ABSTRACT FROM AUTHOR]