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Recombination Lifetime (recombination + lifetime)
Selected AbstractsSubmicron resolution carrier lifetime analysis in silicon with Fano resonancesPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010Paul Gundel Abstract Defect rich regions in multicrystalline silicon are investigated by Raman spectroscopy at high and low injection levels. By analyzing the Fano type asymmetry and the spectral position of the first order Raman peak crucial properties such as recombination lifetime, doping density and stress can be extracted simultaneously. Due to the small wavelength of the excitation laser the spatial resolution of these measurements is significantly below 1 µm, which gives new insight into the impact of defects on the carrier recombination lifetime. The results are evaluated by comparing them to micro-photoluminescence and synchrotron X-ray fluorescence measurements. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Degradation of InGaN-based laser diodes due to increased non-radiative recombination ratePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2010N. Trivellin Abstract With this paper we analyze the correlation between the degradation of InGaN-based laser diodes (LDs) and the increase in the non-radiative recombination rate in the active region. Several 405,nm MOCVD LDs have been submitted to CW stress, for 2000,h (stress current in the range 40,100,mA, case temperature,=,75,°C). During stress, we extensively evaluated the optical characteristics of the LDs: a technique for the evaluation of the non-radiative recombination lifetime (,nr) in the active material was developed and used for the analysis of the stress effects. We demonstrate the following: (1) degradation determines the increase in LDs threshold current (Ith) and the decrease in the ,nr; (2) degradation of Ith and ,nr have similar kinetics; and (3) the degradation rate of the LDs is almost linearly related to the stress current level. The degradation process is therefore ascribed to the decrease of internal quantum efficiency caused by the increase of the non-radiative recombination rate in the active region. [source] Influence of piezoelectric fields on excitonic complexes in InGaN quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2009K. Sebald Abstract We present an analysis of the optical properties of single InGaN quantum dots (QDs) grown by MOVPE. The samples were structured into mesas by focused-ion-beam etching and investigated by micro-photoluminescence measurements. The QDs are characterized by the high temperature stability of their emission up to 150 K. Furthermore, the polarization of individual QD emission lines was analyzed giving an insight into their geometrical shape. Time-resolved microphotoluminescence measurements on the excitonic and biexcitonic transition of a single quantum dot yields a radiative recombination lifetime of 2.06 ns for the exciton. The data can be fitted by a simple model for cascaded emission confirming the expected refilling of the excitonic state by biexcitonic recombination. In addition, the influence of piezoelectric fields on the exciton and biexciton emission and on their binding energy in single QDs was investigated. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Origin of Radiation-Induced Degradation in Polymer Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Ankit Kumar Abstract Polymer solar cells have been shown to degrade under X-rays. Here, in situ polymer photovoltaic performance and recombination lifetimes are measured and it is found that charge accumulation is the primary reason for degradation of solar cells. This is affected by the mixing ratio of donor and acceptor in the bulk heterojunction. Both a quantitative understanding and the physical model of the degradation mechanism are presented. Understanding of the degradation mechanism is extended in polymer donor,acceptor bulk heterojunction systems to propose a material combination for making radiation hard diodes that can find important application in fields ranging from memory arrays to organic X-ray detectors for medical imaging. [source] A simulation-based method for the comprehensive analysis of effective lifetime from photoconductancePROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2007G. Bueno Abstract This paper presents a method for estimating recombination parameters in the volume and surface of solar cell precursors throughout the manufacturing process, taking into account several effects that are generally neglected. The technique is based on the comprehensive reconstruction of the effective lifetime assuming a set of fundamental parameters and its comparison to the experimental data obtained from the photoconductance measured under uniform generation in quasi-steady state conditions. The analysis starts from the semianalytical solution of the minority carrier profiles in the structures under test. This analysis overcomes the usual flat profile approximation and presents important advantages. It allows the asymmetry presented by the solar cell precursors to be taken into account and deals with a wide range of surface conditions: emitters, bare silicon or dielectric passivations. The model also accounts for the effect of the electric field in the volume, and implements several phenomena that are sometimes neglected but are relevant when measuring industrial solar cells precursors: the injection dependence of mobilities and recombination lifetimes, the presence of non-recombinant traps and the Depletion Region Modulation effect. The estimation technique requires uniform generation, which greatly facilitates the calculation of the carrier profiles and allows for a simple method for the auto calibration of the light absorption. Copyright © 2006 John Wiley & Sons, Ltd. [source] |