Browsing by Author "Liao, Jye-Yow"

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Effect of hole blocking dielectric layer on microstructure and photoconducting properties of polycrystalline Se thin films
(2018-09-01)
Chang, Cheng-Yi
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Lin, Yi-Jie
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Huang, Yu-Wei
;
Liao, Jye-Yow
;
Lin, Jian-Siang
We fabricated polycrystalline selenium (c-Se) based photodetectors using three different dielectrics (HfO2, Al2O3 and SiO2) as the hole blocking layer (HBL), and studied the influence of the HBLs on the photoconducting performance of the photodetectors. The microstructure of the c-Se layer is greatly influenced by the nucleation behavior of the tellurium (Te) adhesion layer deposited between the c-Se layer and the HBLs. The photoconducting performance of the photodetectors is basically dependent on the barrier height at the junctions of the HBL with the tin-doped indium oxide (ITO) anode and with the c-Se layer. A higher barrier height at the HBL/ITO junction leads to a lower dark current density (I-D) of the photodetectors. However, the photodetector with the SiO2 HBL exhibits the largest I-D as the bias exceeds 2 V although it has the highest junction barrier height. We attribute the abnormity to the rugged morphology of the c-Se layer, which is a result of a less dense Te nucleation on the SiO2 HBL. The photocurrent density (I-ph) is inversely related to the junction barrier height at the HBL/c-Se contact. The c-Se photodetector with the HfO2 HBL has the largest I-Ph and the one with the SiO2 HBL has the smallest. The photodetector with the HfO2 HBL exhibits a quantum efficiency of 89% at 6 V.
Photoconductive properties of polycrystalline selenium based lateral MISIM photodetectors of high quantum efficiency using different dielectrics as the charge blocking layer
(2019-07-01)
Chang, Cheng-Yi
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Huang, Yu-Wei
;
Lin, Yi-Jie
;
Liao, Jye-Yow
;
Lin, Jian-Siang
We studied the photoconductive performance of polycrystalline selenium (pc-Se) based photodetectors with a lateral metal-insulator-semiconductor-insulator-metal (MISIM) device structure. The insulator layer is a 10 nm-thick Ga2O3, HfO2, or Al2O3 thin film, and used as a charge blocking layer (CBL) to suppress dark current injected from the Al electrodes. The dark current suppression primarily depends on the barrier height of the junctions between the CBLs and electrodes. The Ga2O3 CBL exhibits a poor dark current suppression compared to the HfO2 and the Al2O3 CBLs because of a lower electron barrier at the cathode. The lateral pc-Se photodetectors exhibit a very high internal photocurrent gain due to Fowler-Nordheim tunneling at relatively low applied voltages. The better crystallinity of pc-Se grains formed on the Ga2O3 CBL leads to a higher photoconversion efficiency for the MISIM-Ga2O3 photodetector. Compared with amorphous Se based lateral MISIM photodetectors, the pc-Se photodetectors demonstrate a uniform and much better photoconductive performance over the visible spectrum.