open access

https://doi.org/10.14943/doctoral.k15865

https://hdl.handle.net/2115/94385

アンチモン化インジウムコロイダル量子ドットの合成と表面工学及び短波赤外光フォトダイオードへの応用

英語

SWIR

2024-03-25

Hokkaido University

ii, xix, 95p.

SWIR detection by photodiode has high demand due their photodetection capability beyond visible range. SWIR photodiodes has application from remote-sensing, light-detection ranging (LIDAR), optical telecommunications, bio imaging, infrared and thermal imaging, medical monitoring for healthcare researches. Bulk semiconductors such as InGaAs, InAs, InSb, InAsSb are used as photosensitive active layers for various photodetection. But the high fabrication cost of these complex device structure appeared to be challenging for various applications such as poor spectral tunability, less material choice. Additionally, complex and expensive cooling system also become a blockage for foldable emergent practical infrared application. While the solution processed colloidal semiconductor has various advantages to overcome those issues. It offers bandgap tunability by controlling the diameter of the nanocrystal, which affects the absorption or emission wavelength range for optoelectronics applications for quantum dot light emitting diode, quantum dot photodetectors. Additionally, synthesis of solution processed CQDs is a cost effective wet chemical process where mass production cost could be reduced by multiple factors. Till date Pb and Hg based CQD has been used for SWIR photodetection as the active layer of a photodetector. However, due to their high toxicity according to RoHS-restricted element, it is utmost necessity to find a suitable substitute material for SWIR detection. To evade the toxicity issues, III-V semiconductor based InSb have attracted significant attention due to their absorption in NIR to SWIR wavelength range. Therefore, the thesis focuses on the synthesis of high crystalline impurity less InSb CQDs with readily available halide precursors. Additionally, to improve the carrier mobility for fast charge transfer, long chain Oleylamine (OLA) ligand was exchanged with short chain bromide and sulfide ligands for self-powered SWIR photodiode application. In Chapter 1, general background of SWIR materials, overview about the synthesis of CQDs and figure of merits for photodetection. In details the process, the purpose of this research which led to the urgency of studying InSb CQD for SWIR sensing. Chapter 2 focus on the facile synthesis of InSb CQDs with halide precursor. Unlike to previous all the InSb CQDs synthesise reports, the motivation of this study is to synthesis pure phase impurity-less InSb CQDs with less reactive and easily available and stable precursors. We have used chloride and bromide precursors by following hot-injection synthesis procedure. Additionally, we have compared the product prepared by the two precursors. Chapter 3 fcus on the surface modification by ligand exchange procedure. As Oleylamine (OLA) is a long chain ligand which helps to CQDs dispersed in solution, while it acts as an insulator for charge transfer for device application. That’s why ligand exchange from long to short chain is an important step in solution processed optoelectronic field. Here, ligand exchange was performed by bromide and sulfide ligands to increase carrier mobility and charge transfer between the CQDs. Chapter 4 fcus on the fabrication of InSb CQD based photodiode for SWIR sensing. Here, we have demonstrated first-ever InSb CQD based photodiode for SWIR sensing where bromide capped InSb was used as active layer. The resulting PDs achieve a photoresponse of ~550 ms at 0 V, with combining the best values of responsivity and external quantum efficiency of 0.098 A/W and 10.1% under a bias voltage of −1 V at room temperature even in ambient air. Secondly, to improve the carrier mobility sulfide capped InSb CQD was further used as active layer, QPD responded as self-powered photodiode and achieves 1.3% EQE and responded 200 ms at 0 V, with 18.5% EQE at -1 V under 1100 nm. Chapter 5 proposes future work on al-inorganic InSb CQD with further improvement and conclude the thesis.

2024-03-25

甲第15865号

博士(理学)

(主査) 教授 松井 雅樹, 教授 忠永 清治, 客員教授 野口 秀典, 客員教授 白幡 直人

総合化学院（総合化学専攻）

博士論文

Version of Record