Highly Repeatable and Recoverable Phototransistors Based on Multifunctional Channels of Photoactive CdS, Fast Charge Transporting ZnO, and Chemically Durable Al2O3 Layers

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• 作者：Cheol Hyoun Ahn ; Won Jun Kang ; Ye Kyun Kim ; Myeong Gu Yun ; Hyung Koun Cho
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：June 22, 2016
• 年：2016
• 卷：8
• 期：24
• 页码：15518-15523
• 全文大小：432K
• 年卷期：0
• ISSN：1944-8252

文摘

Highly repeatable and recoverable phototransistors were explored using a “multifunctional channels” structure with multistacked chalcogenide and oxide semiconductors. These devices were made of (i) photoactive CdS (with a visible band gap), (ii) fast charge transporting ZnO (with a high field-effect mobility), and (iii) a protection layer of Al₂O₃ (with high chemical durability). The CdS TFT without the Al₂O₃ protection layer did not show a transfer curve due to the chemical damage that occurred on the ZnO layer during the chemical bath deposition (CBD) process used for CdS deposition. Alternatively, compared to CdS phototransistors with long recovery time and high hysteresis (ΔV_th = 19.5 V), our “multi-functional channels” phototransistors showed an extremely low hysteresis loop (ΔV_th = 0.5V) and superior photosensitivity with repeatable high photoresponsivity (52.9 A/W at 400 nm). These improvements are likely caused by the physical isolation of the sensing region and charge transport region by the insertion of the ultrathin Al₂O₃ layer. This approach successfully addresses some of the existing problems in CdS phototransistors, such as the high gate-interface trap site density and high absorption of molecular oxygen, which originate from the polycrystalline CdS.