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佐藤 真一郎; Schmieder, K.*; Hubbard, S.*; Forbes, D.*; Warner, J.*; 大島 武; Walters, R.*
no journal, ,
インジウム砒素(InAs)量子ドット(QD)を含むガリウム砒素(GaAs)pn接合ダイオードとQDを含まないpnダイオードに対する、3MeV陽子線照射の影響を欠陥準位評価(DLTS)法によって評価した。照射によって生成する欠陥準位のエネルギーと捕獲断面積に加え、照射量の増加に伴う欠陥準位密度の変化について調べた。その結果、照射欠陥に起因すると思われる複数の欠陥準位は照射量に対して比例して増加することが分かった。一方、照射前から存在するEL2トラップと呼ばれる欠陥準位の密度は照射後も増加しないが、照射前におけるQDを含むpn接合ダイオード中のEL2トラップ密度はQDを含まないpn接合ダイオードよりも数倍高くなっており、EL2トラップ密度の改善が今後の課題であることが判明した。
大島 武; 中村 徹哉*; 住田 泰史*; 今泉 充*; 佐藤 真一郎; 菅谷 武芳*; 松原 浩司*; 仁木 栄*; 望月 透*; 岡野 好伸*
no journal, ,
Introduction of highly-stacked well-aligned Quantum Dots (QDs) layers into solar cells are expected to realize their extremely high conversion efficiency. In this study, the current induced in QD solar cells by 1 MeV electron irradiation was evaluated to investigate their degradation response. The samples used in this study were GaAs PiN solar cells with InGaAs QD layers by molecular beam epitaxy (MBE). For comparison, GaAs PiN solar cells with an i-layer were fabricated under the same process without the fabrication of the QD layers. The QD and non QD solar cells were irradiated with 1MeV electrons and their electron-induced currents were measured at applied bias between -300 and 200 mV. As a result, QD solar cells showed applied bias dependence of electron-induced current, and the value of electron-induced current increased with increasing reverse bias. Also, with increasing electron fluence, the electron-induced current decreased. This can be interpreted in terms of a decrease in carrier lifetime due to radiation induced defects. The applied bias dependence for QD solar cells became larger with increasing electron fluence. On the other hand, non QD solar cells did not show the applied bias dependence of electron-induced current before and after irradiation. These results suggest that carriers generated in QD solar cells by electrons recombine in QD layer when the electric field is not high enough.