藉由優化光柵結構提高多彩量子井與超晶格紅外線光偵測器之響應度

Abstract

量子井紅外線光偵測器在各領域中被廣泛應用，其中包含天文、醫療、建築、軍事、安全系統等領域。本論文通過添加超晶格結構與光柵結構，以提高元件的光吸收效率。 光柵的作用可使光能大量集中於基板主動層，增加光電流，並能大幅增加元件之光吸收率。超晶格的結構可使電子容易被光激發，讓元件可以在低偏壓下操作，其電阻小，可以有效降低暗電流並減少雜訊產生。本論文也通過改變光柵蝕刻深度，藉此改變光場的能量分佈，使光場集中於主動層，提高元件之響應度。 我們發現當光柵週期固定於2μm時，光柵深度與響應度之間的關係並不是遞增函數，而是在深度為1.3μm時達響應度之最佳值，與沒有光柵結構的元件相比較，有2.5倍的增益。最佳深度為1.3μm之光柵結構最高操作溫度可以量測到83K。

Quantum wells Infrared photodetector have been widely used in many fields, such as astronomy, medical, construction, military, security systems and etc. In our study, superlattice structure is added in order to enhance light absorption efficiency. Grating structure can also improve responsivity. The effect of grating system not only can concentrate light energy and then improve the photocurrent, but also can greatly increase its absorption in the active layer. Superlattice structure can help electrons easily excited by photons, which make our device can be operated at low bias voltage. Due to the small resistance, the dark current can be effectively reduced and then reduce the noise generation. Another study is to enhance responsivity of the photo detector by changing grating depth. We find that as the period of grating structure is fixed at 2μm, the relationship between the grating depth and the responsivity is not an increasing function. According to the results, the optimal value of the responsivity is detected when the grating depth is 1.3 μm. Compared with the devices without the grating structure, our best device had 2.5 times of the gain. The maximum operation temperature of our best device is measured at 83K.