| AVS 61st International Symposium & Exhibition | |
| Thin Film | Wednesday Sessions |
| Session TF+EM+EN-WeA |
| Session: | Thin Film and Nanostructured Coatings for Light Trapping, Extraction, and Plasmonic Applications |
| Presenter: | Ali Haider, Bilkent University, Turkey |
| Authors: | A. Haider, Bilkent University, Turkey N. Biyikli, Bilkent University, Turkey A.K. Okyay, Bilkent University, Turkey T. Karabacak, University of Arkansas at Little Rock H. Cansizoglu, University of Arkansas at Little Rock B. Teckcan, Bilkent University, Turkey M.F. Cansizoglu, University of Arkansas at Little Rock |
| Correspondent: | Click to Email |
Improved charge carrier collection and optical absorption are two main techniques to enhance the photocurrent of a nanostructured photodetector. In a nanostructured photodiode, longer carrier life time and shorter transit time of the photo-generated carriers provides efficient charge carrier collection while the nanostructured device architecture contributes towards trapping the light by diffuse light scattering and enhancing optical absorption. However, efficient charge carrier collection is limited by the random and non-uniform nano-network. For nanostructured Schottky photodetectors, uniform nanostructured geometries with larger aspect ratio can enhance the interface of the Schottky junction which in turn decreases the transit time of generated carriers. In addition, most of the nanofabrication methods that can produce uniform nanostructure geometries are limited to certain materials. Therefore, it is an overwhelming demand to develop innovative low-cost nanostructured photodetector fabrication methodologies which enables the use of a variety of semiconductor alloy families with uniform and optimized geometries for improving photoresponsivity performance. In this work, we demonstrate a proof-of-concept nanostructured Schottky photodiode fabrication method combining glancing angle deposition (GLAD) and atomic layer deposition (ALD) to fabricate metal-semiconductor radial junction nanorod arrays, which offers significantly enhanced photoresponse compared to conventional planar counterpart. Firstly, silver (Ag) nanorod (NR) arrays were deposited on Ag thin film/Si templates by utilizing glancing angle deposition (GLAD) technique. A conformal and thin titanium dioxide (TiO2) coating was deposited on silver nanorods via ALD. ALD emerge as highly attractive deposition technique for coating of nanorods due to its remarkable conformality and uniformity on the densely packed NR structures. Moreover, ALD also facilitates the ultra-precise control of deposited film thickness in the sub-nm scale. Following the growth of TiO2 on Ag NRs, aluminum (Al) metallic top contacts were deposited by thermal evaporation to complete the fabrication of NR-based Schottky photodiodes. Due to the improved charge carrier collection and optical absorption, the resulting nanostructured detector exhibits a more-than two orders of magnitude photoresponsivity enhancement factor (3.8x102) under 3V reverse bias when compared to the corresponding thin film counterpart device with the same TiO2 thickness. Our preliminary structural, optical, electrical, and photoresponse characterization results are presented.