微共振腔量子點紅外線偵測器

Abstract

從一些文獻得知，微共振腔結構在某些共振條件下可以使光耦合進共振腔中達到共振。在本篇論文中，我們將此結構運用在量子點紅外線偵測器上，製作出一微共振腔量子點紅外線偵測器(MCQDIPs)，我們將砷化鎵樣品薄化，並且在正面外加金屬光柵和在背面鍍上金屬，其作用是提供光的反射與產生表面電漿子。 設計其結構共振波長與元件吸收波長相同，使偵測器在波長8微米的響應能增強，並且偵測度也有效提升。在實驗結果中，溫度20K時，其不同偏壓下達到共振的MCQDIPs光響應與一般無結構的QDIPs相比，提高了約35~60倍，不同偏壓下達到共振的MCQDIPs光響應與沒有達到共振的MCQDIPs相比，提高了約18~30倍。 此外在溫度77K時量測其不同元件的偵測度，不同偏壓下MCQDIPs偵測度與單純只有薄化加背金，且表面沒有金屬光柵的QDIPs相比，提高了10倍，其原因是暗電流並不會受到微共振腔的影響，但光響應卻能大大提升，因此偵測度提高。

It is known that micro cavities on enhance the absorption of a photodetector if certain resonant conditions are met. In this thesis we applied this idea to quantum dot infrared photodetectors (QDIPs) for long wavelength infrared detection. The microcavities were formed by thinning down the sample thickness to micron scale. The back metal and the surface metal gratings provide the necessary feedback for resonance. By properly design the micro-cavity, we are able to match the resonant wavelength to our QDIPs’ absorption peak, which is at 8 m. The responsivities and the detectivities were both enhanced greatly compared with those without the microvities. Compared with the reference structure (QDIPs without any cavity structure), the responsivity is enhanced by 35~60 times at different bias at 20K. Compared with the MCQDIPs structure which is non-resonant, the responsivity enhancement is about 18~30 times. Even with the complicate process steps, the dark current of the devices with microcavities remained the same as those without microcavities. So the detectivities are also enhanced. The enhancement in detectivity of QDIPs with the full microcavity design is more than 10 times at 77K comparing with the devices without surface gratings.