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標題: | 分子束磊晶成長之銻基材料及其奈米結構 Antimony Based Materials and Nanostructures Prepared by Molecular Beam Epitaxy |
作者: | Hsuan-An Chen 陳璿安 |
指導教授: | 林時彥(Shih-Yen Lin) |
關鍵字: | 分子束磊晶,銻化鎵量子環,銻化鎵/砷化銦型態二超晶格,紅外線偵測器,銻烯,二維材料, Molecular Beam Epitaxy,GaSb Quantum Rings,InAs/GaSb Type-II Superlattices,Infrared Photodetectors,Antimonene,2D Materials, |
出版年 : | 2018 |
學位: | 博士 |
摘要: | 本論文主要係藉由分子束磊晶成長銻基材料及其奈米結構,分為三大部份探討:銻化鎵量子環及其複合量子奈米結構、銻化鎵/砷化銦型態二超晶格紅外線偵測器及石墨烯在紅外線區段之透明電極之應用、單晶銻烯成長及其接觸電阻降低之元件應用。在銻化鎵奈米結構的部份,我們藉由週期性間歇的成長手法成長出銻化鎵量子點,並在執行成長後浸潤程序時,利用銻/砷混合分子束之比例進而調控銻化鎵量子點或量子環之形成。銻化鎵量子環擁有較大的接觸面積進行電子電洞再覆合,使得我們在室溫下即可觀察到其擁有光致螢光的發光強度。後續我們以銻化鎵量子環佐砷化銦量子點形成複合量子奈米結構,並探討砷化銦量子點與銻化鎵量子環在不同厚度的砷化鎵間隔下的表面形貌、成長機制以及發光特性。從發光特性演變可以看到此複合奈米結構產生紅移現象並在室溫下發出1.4微米波長的光致螢光,進而發現載子生命週期由型態一砷化銦量子點結構的1.1奈秒轉變到型態二複合奈米結構的234奈秒。對於銻化鎵/砷化銦型態二超晶格紅外線偵測器,我們藉著置入銻化銦之應變緩衝層於砷化銦/銻化鎵介面間抵消拉伸應力,使得不含有殘留應力的銻化鎵/砷化銦型態二超晶格結構得以實現。並對於極少層數的三十層型態二超晶格紅外光偵測器,我們透過尺寸微縮來增進頻譜響應強度以及檢偵度。其展現了在絕對溫度150 K以內的高工作溫度,皆可以保持大於1010 cm•Hz1/2/W的高檢偵度。同時我們也建構了單偵測器熱影像掃描系統,體現了型態二超晶格紅外光偵測器在於熱影像應用上的可行性。但在尺寸微縮過程中我們發現頻譜響應強度以及檢偵度隨著載子傳輸路徑降低載子再復合的機會而隨之下降。而我們藉由傳輸線模型,瞭解到雙層石墨烯可與一般金/鈦電極有同樣的接觸電阻,而藉由1.3到22.2微米波長的穿透頻譜瞭解到其擁有95 %以上的穿透率。以上皆指出石墨烯有著作為超廣能帶波長的透明電極潛力,我們應用石墨烯作紅外線透明電極之用,讓載子傳輸路徑最小化以提升載子收集效率,使得元件特性不受到感光尺寸的影響,於絕對溫度150 K下,各個感光尺寸的元件至少保持大於109 cm•Hz1/2/W的高檢偵度。最後我們嘗試作單晶銻烯的成長,先於藍寶石基板上觀察到在200 oC熱退火之後僅能得到單晶銻烯碎塊,同時其與基板有著大的接觸角,接著我們以雙層二硫化鉬/藍寶石樣品作為新基板進行成長,在200 oC的低溫下成功成長出晶圓尺寸的單晶銻烯薄膜。而由泛函密度理論分析可以得知銻烯在二硫化鉬上的介面能遠低於在藍寶石基板上的介面能。而利用介面能的差異,我們也成功作出選擇性成長,並成長出銻烯/二硫化鉬陣列圖形於藍寶石基板上,與此同時利用二硫化鉬的化學抗性開發出銻烯選擇性蝕刻。最後應用銻烯於二硫化鉬上,成功改善二維材料與電極的特徵接觸電阻過高的問題,進而展現在二硫化鉬電晶體上開路電流以及載子遷移率之增長。 Molecular beam epitaxy (MBE) is adopted for epitaxially grown antimony based materials and nanostructures in this thesis. There are three main research directions under this topic. They are GaSb quantum dots (QDs)/rings and their hybrid nanostructures, InAs/GaSb type-II superlattice infrared photodetectors (T2SLs) and single-crystal 2D material antimonene films prepared by MBE. On the preparation of GaSb nano-structures, by using periodical growth interrupts, precise coverage control can be achieved for GaSb quantum rings growth by using a single Ga effusion cell. With direct As irradiation to the substrate surface during the post soaking time, the soaking time can be effectively reduced while full ring morphologies and room-temperature QR luminescence can still be observed by using this method. Furthermore, we grew the GaSb quantum rings coupled with InAs quantum dots as the new hybrid quantum nanostructures, and investigated the morphology, growth mechanism and optical characteristic of the hybrid structures with different GaAs spacer layer thickness. The luminescence wavelength of the hybrid nanostructures is red-shifted to 1.4 μm at room temperature. Compared with type-I InAs QDs (carrier lifetimes ~1.1 ns), the new hybrid quantum nanostructures show the much longer carrier lifetimes (~234 ns), which are a result of further reduced wave-function overlap between QD conduction states and QR valence counterparts. On the GaSb/InAs T2SL infrared photodetectors, we have demonstrated the strain-compensated GaSb/InAs superlattice structures by inserting a monolayer InSb as the strain compensator layer into the GaSb/InAs superlattice. We have also demonstrated enhanced responsivity and detectivity values for short 30-period InAs/GaSb T2SL infrared photodetectors with reduced device areas. High detectivity over 1010 cm•Hz1/2/W up to 150 K observed for the device with the smallest device area has revealed the potential of T2SL photodetectors in high-temperature operation. The thermal images obtained by using a single-detector raster scanning system have revealed the potential of the T2SL infrared photodetector for this application. The results may also demonstrate that with longer transporting lengths, higher recombination probability of photo-excited carriers with surface states may decrease the devices’ responsivity and detectivity values. With the aid of the transparent electrode graphene showing the low specific contact resistance with p-type GaSb and the high transmittance larger than 95 % in the infrared light range of 1.3 to 22.2 μm, we have demonstrated the potential of graphene as a promising candidate for infrared transparent electrodes. Finally, we have tried to achieve single-crystal 2D material antimonene growth by using MBE. On blank sapphire substrates, only single-crystal antimonene flakes with large wetting angles can be obtained after the 300 oC post-growth annealing procedure of amorphous antimony (Sb) droplets at room temperature. By using a bilayer MoS2/sapphire sample as the new substrate, a continuous and single-crystal antimonene film is obtained at a low growth temperature of 200 oC. The results are consistent with the theoretical prediction of the lower interface energy between antimonene and MoS2. The different interface energies of antimonene between sapphire and MoS2 surfaces lead to the selective growth of antimonene only atop MoS2 surfaces on a pre-patterned MoS2/sapphire substrate. Besides the potential application in electronic devices for thin antimonene, the significant (3 orders of magnitude) specific contact resistance reduction of Au/antimonene electrodes on MoS2 surfaces suggest that improved performances can be obtained for 2D material devices with a conducting 2D material such as antimonene as the contact metal. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/69124 |
DOI: | 10.6342/NTU201801803 |
全文授權: | 有償授權 |
顯示於系所單位: | 電子工程學研究所 |
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