ァモルファスセレンとダイヤモンド冷陰極を用いた光検出器の評価

摘要

アモルファスセレン(a-Se)を用いた光検出器は，高い位置分解能と応答速度を兼ね備え，さらにキヤリア増倍による高感度化が可能であるという利点を有する.近年開発されている，HARPと平面電子源(Field Emitter Array: FEA)を組み合わせたデバイスは，熱陰極を用いたHARP撮像管に比べ，大幅な小型化を実現しているが，放出電子線の収束や高光量時の信号飽和によるダイナミックレンジの制限などに課題が残されている.本研究では，信号読み出しにダイヤモンド冷陰極を用いることで既存光検出器の課題解決を目指し，窒素添加ダイヤモンド冷陰極とa-Se薄膜を組み合わせた光検出器を試作した.可視光及び紫外光照射下での電流-電圧特性から，これらの光の検出を確認した.また，ダイヤモンドのバルタ抵抗によるとみられる電流飽和が観察された.%Amorphous-selenium(a-Se)based photodetectors are promising candidate for high sensitivity photo imaging devices, due to their high spatial resolution and response speed, as well as extremely high sensitivity enhanced by an internal carrier multiplication. HARP(high-gain avalanche rushing photoconductor)is the first a-Se based photodetector, which exploited the carrier multiplication and achieved effective quantum efficiency of greater than 10 with real-time imaging capability. Although recent FEA(Field Emitter Array)-HARP achieved significant reduction of device size and power consumption, these devices are still being developed due to remaining problems. Such problems include resolution loss caused by dispersion of emitted electrons, as well as narrower dynamic range because of limited emission current. In this study we attempt to solve the current issues in high-sensitivity a-Se based photodetector, by using diamond cold cathode. A prototype photodetector has been developed using nitrogen-doped diamond as cold cathode, and characterized by visible/UV light illumination.