Papers by Keyword: Recombination Current

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Authors: Hwen Fen Hong, Jin Wei, Mei Hui Chiang, Zun Hao Shih, Wu Yih Uen, Yi Ru Hsu, Cheng Ban Chung, Yueh Mu Lee
Abstract: We analyzed the degradation mechanism of GaInP/GaInAs/Ge triple junction solar cells without coating any protective film. Gradual degradation in the dark and light I-V characteristics of the solar cells were observed after the step stress accelerated degradation tests (SSADT) were conducted on these devices sequentially at 90, 110, 130 and 150°Cfor 25, 55, 85 and 135 hours, respectively. The recombination current in the depletion region at the chip perimeter of solar cells, resulting in the decrease of open-circuit voltage (VOC), fill factor (FF) and efficiency, is suggested to be the important degradation mechanism for GaInP/GaInAs/Ge triple junction solar cells.
Authors: Anatoly M. Strel'chuk, Anton E. Kalyadin, Alexander A. Lebedev, Vitalii V. Kozlovski, Leonid P. Romanov, Victor A. Petrov
Abstract: A study of how electron irradiation affects the current-voltage (I-V) and electroluminescence (EL) characteristics of two types of 4H-SiC n+p structures with p-base and base doping to ~5∙1015 cm-3 is presented. The characteristics were measured prior to irradiation and after each of five stages of irradiation with 0.9 MeV electrons at doses in the range from 1∙1015 to 1.1∙1016 cm-2. The irradiation leads to an increase in the recombination current, decrease in the intensity of the edge EL (hνmax≈3.18 eV), and increase in the intensity of the infra-red (IR) EL (hνmax≈1.35 eV), which starts to predominate. Presumably, this indicates that the nonequilibrium carrier lifetime decreases and the concentration of acceptor type defects grows as a result of the irradiation. The IR EL, attributed to a complex defect containing a silicon vacancy, is of interest for development of single-photon sources of light.
Authors: Anatoly M. Strel'chuk, V.T. Gromov, Viktor V. Zelenin, A.N. Kuznetsov, Alexander A. Lebedev, N.G. Orlov, N.S. Savkina, V.P. Shukailo
Abstract: Neutron irradiation (~1 MeV, dose 1014-5.6∙1015 neutron/cm2) of packaged diodes based on 6H-SiC pn structures (with the base n-layer doped to ~5∙1016 cm-3) has been studied. In addition to the well-known rise in the series resistance of the diodes, the effect of a partial suppression of the excess current in both forward-and reverse-biased diodes and that of an increase in the recombination current, probably associated with the decrease in the nonequilibrium carrier lifetime, were discovered and discussed. These effects are common to 6H-and 4H-SiC pn structures.
Authors: Otwin Breitenstein, Jan Bauer, Pietro P. Altermatt, Klaus Ramspeck
Abstract: The current-voltage (I-V) characteristics of most industrial silicon solar cells deviate rather strongly from the exponential behavior expected from textbook knowledge. Thus, the recombination current may be orders of magnitude larger than expected for the given material quality and often shows an ideality factor larger than 2 in a wide bias-range, which cannot be explained by classical theory either. Sometimes, the cells contain ohmic shunts although the cell’s edges have been perfectly insolated. Even in the absence of such shunts, the characteristics are linear or super-linear under reverse bias, while a saturation would be classically expected. Especially in multicrystalline cells the breakdown does not tend to occur at -50 V reverse bias, as expected, but already at about -15 V or even below. These deviations are typically caused by extended defects in the cells. This paper reviews the present knowledge of the origin of such non-ideal I-V characteristics of silicon solar cells and introduces new results on recombination involving coupled defect levels.
Authors: Anatoly M. Strel'chuk, Evgenia V. Kalinina
Abstract: Presented in this paper are the results of a study of forward and reverse current-voltage characteristics of the 4H-SiC pn structures produced by implantation of Al+ ions in low-doped ((5-7)∙1014cm-3) n-type conductivity epitaxial layer. A forward current was identified which is consistent with the model of recombination in the space charge region of a pn junction via a deep level: J=Joexp(qU/nkT), where Jo=Jo*exp[-Ea/(kT)] (or J= Jo*exp[(qU-2Ea)/nkT)]) with the ideality factor n=2. Parameters of this current are as follows: Jo(293 K) ~ 8∙10-25 A/cm2, Ea 1.73-1.75 eV (2Ea3.46-3.5 eV), Jo*~7∙105 A/cm2. A comparison of the experimental and model-based values of Ea, with allowance for all clearly defined temperature dependences, both strong and weak, of the model of recombination in the space charge region shows that the effective lifetime increases and effective trapping cross section σeff of the recombination level decreases with increasing temperature: σeff ~ T-2÷σeff ~ T-2.5 or σeff ~exp(ΔE /kT) where ΔE=80-100 meV. Reverse current practically in whole temperature range is excess current, only at high temperatures (~800 K) reverse current became close to generation current in space charge region. Special interest are the excess currents as a result of the application of a reverse or forward voltage at high temperature. The barrier type excess currents is characteristic of SiC.
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