Lateral amorphous selenium metal-insulator-semiconductor-insulator-metal photodetectors using ultrathin dielectric blocking layers for dark current suppression

• Published in: Journal of applied physics 2016-12, Vol.120 (23)
• Main Authors: Chang, Cheng-Yi, Pan, Fu-Ming, Lin, Jian-Siang, Yu, Tung-Yuan, Li, Yi-Ming, Chen, Chieh-Yang
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Applied physics; Chemical vapor deposition; Dark current; Dielectrics; Electric fields; Hafnium oxide; Insulators; MIS (semiconductors); Organic chemistry; Photometers; Selenium; Silicon nitride
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4972029

We fabricated amorphous selenium (a-Se) photodetectors with a lateral metal-insulator-semiconductor-insulator-metal (MISIM) device structure. Thermal aluminum oxide, plasma-enhanced chemical vapor deposited silicon nitride, and thermal atomic layer deposited (ALD) aluminum oxide and hafnium oxide (ALD-HfO2) were used as the electron and hole blocking layers of the MISIM photodetectors for dark current suppression. A reduction in the dark current by three orders of magnitude can be achieved at electric fields between 10 and 30 V/μm. The effective dark current suppression is primarily ascribed to electric field lowering in the dielectric layers as a result of charge trapping in deep levels. Photogenerated carriers in the a-Se layer can be transported across the blocking layers to the Al electrodes via Fowler-Nordheim tunneling because a high electric field develops in the ultrathin dielectric layers under illumination. Since the a-Se MISIM photodetectors have a very low dark current without significant degradation in the photoresponse, the signal contrast is greatly improved. The MISIM photodetector with the ALD-HfO2 blocking layer has an optimal signal contrast more than 500 times the contrast of the photodetector without a blocking layer at 15 V/μm.