Fast-timing study of the -forbidden 1/2 3/2 transition in Sn

Lic, R.*; Mach, H.*; Fraile, L. M.*; Gargano, A.*; Borge, M. J. G.*; Mrginean, N.*; Sotty, C. O.*; Vedia, V.*; Andreyev, A. N.; Benzoni, G.*; et al.

Physical Review C, 93(4), p.044303_1 - 044303_7, 2016/04

https://doi.org/10.1103/PhysRevC.93.044303

Identification of deformed intruder states in semi-magic Ni

Chiara, C. J.*; Weisshaar, D.*; Janssens, R. V. F.*; Tsunoda, Yusuke*; Otsuka, Takaharu*; Harker, J. L.*; Walters, W. B.*; Recchia, F.*; Albers, M.*; Alcorta, M.*; et al.

Physical Review C, 91(4), p.044309_1 - 044309_10, 2015/04

https://doi.org/10.1103/PhysRevC.91.044309

The neutron-rich isotope Ni was produced by multi-nucleon transfer reactions of Zn in the Argonne National Laboratory, and an in-beam -ray experiment were performed using the GRETINA array. The and levels of Ni were observed for the first time. Those levels are regarded as large deformed states associated with proton excitation from the orbit because they cannot be reproduced by a shell-model calculation assuming a small valence space without . A theoretical analysis based on the Monte Carlo shell model published in 2014 indicates that those levels corresponds to a prolate deformed band. The present result demonstrates the occurrence of shape coexistence in neutron-rich Ni isotopes other than a known case of Ni, and confirms the predictive power of the Monte Carlo shell-model calculation.

Effect of irradiation on gallium arsenide solar cells with multi quantum well structures

Maximenko, S.*; Lumb, M.*; Hoheisel, R.*; Gonzlez, M.*; Scheiman, D.*; Messenger, S.*; Tibbits, T. N. D.*; Imaizumi, Mitsuru*; Oshima, Takeshi; Sato, Shinichiro; et al.

Proceedings of 40th IEEE Photovoltaic Specialists Conference (PVSC-40) (CD-ROM), p.2144 - 2148, 2014/06

https://doi.org/10.1109/PVSC.2014.6925349

In this paper, a complex analysis of the radiation response of GaAs solar cells with multi quantum wells (MQW) incorporated in the i-region of the device is presented. Electronic transport properties of the MQW i-region were assessed experimentally by the electron beam induced current (EBIC) technique. A 2-D EBIC diffusion model was applied to simulate EBIC line scans across device structure for different radiation doses. The results are interpreted using numerical modeling of the electrical field distribution at different radiation levels. Type conversion from n- to p-type was found in MQW i-region at displacement damage dose as low as low as 1 MeV MeV/g. This is supported by experimental and simulated EBIC and electric field distribution results.

Radiation study in quantum well III-V multi-junction solar cells

Gonzlez, M.*; Hoheisel, R.*; Lumb, M.*; Scheiman, D.*; Bailey, C. G.*; Lorentzen, J.*; Maximenko, S.*; Messenger, S. R.*; Jenkins, P. P.*; Tibbits, T. N. D.*; et al.

Proceedings of 39th IEEE Photovoltaic Specialists Conference (PVSC-39) (CD-ROM), p.3233 - 3236, 2013/06

https://doi.org/10.1109/PVSC.2013.6745141

The radiation response of multi quantum wall (MQW) triple junction and component cells was analyzed. Initial results show that for 1MeV electron irradiation the middle MQW cell governs the degradation of the triple junction. This is attributed the specific middle cell design, in particular the thick 0.98 m depletion region, and alternative, more radiation hard, designs are presented. Additionally, characterization studies, including dark IV, external quantum efficiency, electroluminescence, as well as defect characterization were investigated.

In situ irradiation and measurement of triple junction solar cells at Low Intensity, Low Temperature (LILT) conditions

Harris, R. D.*; Imaizumi, Mitsuru*; Walters, R. J.*; Lorentzen, J. R.*; Messenger, S. R.*; Tischler, J. G.*; Oshima, Takeshi; Sato, Shinichiro; Sharps, R. P.*; Fatemi, N. S.*

IEEE Transactions on Nuclear Science, 55(6), p.3502 - 3507, 2008/12

https://doi.org/10.1109/TNS.2008.2006971

The performance of triple junction InGaP/GaAs/Ge solar cells have been studied following low temperature irradiation while using low intensity illumination. High energy electron and proton irradiations have been performed with cell characterization carried out in situ at the irradiation temperature with no intermediate temperature changes. As such, these conditions reflect those found for deep space, solar powered missions that are far from the sun. Cell characterization consisted of I-V measurements which permitted the extraction of the four principle solar cell parameters: short circuit current, open circuit voltage, maximum power, and fill factor. In addition, quantum efficiency measurements were made prior to and following the irradiations. The low temperature irradiations were followed by a room temperature anneal to determine if any subsequent recovery was present.

Irradiation and measurement of GaAs based solar cells at low intensity, low temperature (LILT) conditions

Walters, R. J.*; Harris, R. D.*; Imaizumi, Mitsuru*; Lorentzen, J. R.*; Messenger, S. R.*; Tischler, J. G.*; Oshima, Takeshi; Sato, Shinichiro; Sharps, R. P.*; Fatemi, N. S.*

Proceedings of the 8th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-8), p.105 - 108, 2008/12

The performance of triple junction InGaP/GaAs/Ge space solar cells was studied following high energy electron irradiation at low temperature. Cell characterization was carried out at the irradiation temperature while using low intensity illumination, and, as such, these conditions reflect those found for deep space, solar powered missions that are far from the sun. Cell characterization consisted of I-V measurements and quantum efficiency measurements. The low temperature irradiations caused substantial degradation that differs in some ways from that seen after room temperature irradiations. The short circuit current degrades more at low temperature while the open circuit voltage degrades more at room temperature. A room temperature anneal after the low temperature irradiation produced a substantial recovery in the degradation.

Quantum well solar cells for space; The Impact of carrier removal on end-of-life device performance

Hoheisel, R.*; Gonzlez, M.*; Lumb, M.*; Scheiman, D.*; Messenger, S. R.*; Bailey, C. G.*; Lorentzen, J.*; Tibbits, T. N. D.*; Imaizumi, Mitsuru*; Oshima, Takeshi; et al.

no journal, , 

In this paper a detailed analysis on the radiation response of solar cells with multi quantum-wells (MQW) included in the quasi-intrinsic region between the emitter and the base layer is presented. Whilst the primary source of radiation damage of photovoltaic devices is generally associated with minority carrier lifetime reduction, we found that in the case of MQW devices another effect of radiation damage, the so called carrier removal (CR) requires additional consideration. Experimental measurements and numerical simulations reveal that with increasing radiation dose, CR can alter the initially quasi-intrinsic background doping of the MQW region to become further n or p type. This can result in a significant narrowing and even in a collapse of the electrical field between the emitter and the base where the MQWs are located. Eventually, remarks for improved radiation hard MQW device designs are provided.

Defect levels in GaAs pn diodes embedded with InAs quantum dot layers

Sato, Shinichiro; Schmieder, K.*; Hubbard, S.*; Forbes, D.*; Warner, J.*; Oshima, Takeshi; Walters, R.*

no journal, , 

III-V semiconductor devices embedded with quantum dots (QDs) are expected to be applied to next generation space solar cells. High density QDs and highly stacked QD layers without stacking fault are required in order to relaize QD solar cells, and have been obtained recently by using strain compensating technology. However, larger amount of defects are still incorporated into QD devices compared to single crystal devices and affect the device characteristics. In this study, we fabricated GaAs pn diode with 10 layers of InAs QDs by Metal Organic Vapor Phase Epitaxy (MOVPE) method and characterized defect levels in the devices using Deel Level Transient Spectroscopy (DLTS). The results were compared to reference samples which were GaAs pn diodes without InAs QDs. It was shown that unique electron and hole trap levels were found in the QD devices and thus we concluded that these traps should be reduced in order to improve the device quality.