型態二砷化銦/銻化鎵超晶格紅外線二極體偵測器在熱影像的應用

Abstract

在本篇論文中，我們研究了30層的型態二5 MLs砷化銦/5 MLs銻化鎵超晶格紅外光二極體偵測器。超晶格結構成長的關鍵點在於緩衝層的粗糙度以及結構中應變的問題。由於銻化鎵緩衝層位於超晶格結構的下方，因此超晶格結構的品質將與緩衝層的粗糙度息息相關。而因為砷化銦及銻化鎵有些微的晶格不匹配，會造成超晶格結構中產生拉伸的應變，此時我們加一層銻化銦在其中，使其中的拉伸應變可以經由銻化銦的厚度而消除。樣品經由製程成為元件，也顯示出在10 K的環境下，會有截止波長在4.2微米的吸收，且元件可以操作在高達200 K的環境下，以及擁有1010 cm·Hz1/2/W以上的檢偵度。接著也探討了不同感光區域尺寸的元件特性，當元件尺寸被縮小時，會發現其光電特性的表現更好，包括擁有更高的響應度及更低的暗電流。最後光電二極體元件在本篇論文展現出其應用，經由熱影像掃描系統，攝氏200度的烙鐵頭經由二極體元件掃描為熱影像，而對於熱影像之高檢偵度，使得型態二砷化銦/銻化鎵超晶格紅外光二極體元件將會是光電偵測器之極佳的候選人。

30-period Type-II 5 MLs InAs/5 MLs GaSb superlattice infrared photo-diodes (T2SL) are investigated in this thesis. The key issues of the superlattice growth are the roughness of the buffer layer and the strain in the superlattice structure. Due to buffer layer GaSb is beneath the superlattice structure, the quality of superlattice is highly related to the roughness of the buffer layer. To compensate the tensile strain of the InAs/GaSb superlattice structures and prevent GaAs formation due to the severe As-for-Sb exchanges, 1 mono-layer (ML) InSb layer was embedded in each GaSb-to-InAs interface, which would lead to an almost strain-free T2SL structure. With sulfur passivated surfaces to depress the large surface leakage currents, the T2SL photo-diode has a 4.2 m cut-off wavelength at 10 K. High operation temperature up to 200 K and detectivity values over 1010 cm·Hz1/2/W are observed for the device. The performances of the photo-diodes with different device areas are also investigated. With reduced device areas, higher responsivity values and lower dark currents are observed. By using a single-detector scanning system, the thermal image of a 200 oC hot solder head is obtained by using the T2SL photo-diode at 77 K. The results have demonstrated the potential of the T2SL photo-diodes for thermal image application.