Black silicon (b‐Si) featured by anti‐reflective surfaces is extensively studied to realize highly sensitive photodetectors. The key to augmenting the light‐detection capability of b‐Si is to facilitate charge extraction while limiting undesired recombination events at surface defects. To this end, oxidative chemical vapor deposition (oCVD) is leveraged to form a highly conformal and conductive (3000 S cm−1) organic transport layer, poly(3,4‐ethylenedioxythiophene) (PEDOT), on b‐Si nanostructures. The oCVD PEDOT instrumentally extracts photo‐induced charges, through which b‐Si photodetectors implementing oCVD PEDOT achieve a superior photo‐detectivity of 1.37 × 1013 Jones. Furthermore, by engineering the pore dimension of b‐Si, a mode‐tunable Si photodetector is contrived, where the functions of broad‐band and visible‐blinded modes are switched facile by a bias polarity. The unprecedented device paves the way for extending the applications of Si detectors toward novel sensory platforms such as night‐vision, motion tracking, and bio‐sensing.
Amorphous oxide semiconductor (AOS) thin film transistors (TFTs) based on In2O3 have attracted much interest for use as pixel switching elements in next generation active-matrix liquid crystal (AM-LCD) and active-matrix organic light emitting diode (AM-OLED) displays. The high field effect mobility of In2O3-based AOS devices (10–25 cm2/Vsec) offers significant performance improvements over present-day a-Si TFTs (<1 cm2/Vsec) technology. Additional advantages of AOS materials include low temperature processing (RT–300 °C), isotropic wet etch characteristics, and high optical transparency (>85 % in the visible regime) all of which make this material suitable for large area, flexible, and transparent devices on inexpensive polymer substrates. There have been considerable efforts to incorporate AOSs into devices, particularly in current-driven active matrix displays such as organic light emitting diode displays as pixel-driving switching elements. Strategies to enhance amorphous phase stability, reduce bias stress-induced threshold voltage shifts, and suppress channel carrier densities have been studied and successfully applied to the switching TFT application. Third cation elements are often added to binary cation oxide systems to limit the channel carrier generation for TFT channel application. We have recently reported that the addition of Al to InZnO, a typical binary cation material system leads to enhanced amorphous phase stability, carrier suppression capability and higher carrier mobility, up to ~45 cm2/Vs (Hall Effect mobility) and ~20 cm2/Vs (field effect mobility)1. All of these characteristics are expected to be a key enabler for realizing the next generation ultra-high-definition displays. Post-process annealing is widely employed in AOS-based TFT fabrication since annealing has been shown to improve field effect mobility2-3 and channel/metallization contacts4-5 as well as reduce trap density6, which often leads to unstable device performance or unfavorable hysteresis in their transistor characterstics6-7. However, the post-annealing is often accompanied by an increase in channel carrier density that induces an unfavorable increase in the device off-state current and operation voltages2, 8. To date, the origin of the increase in channel carrier density has not been fully understood. The current study aims to identify the origin of an increase in carrier density after low-temperature annealing conducted in air, particularly for a third-cation AOS system of InAlZnO (IAZO). Through work function investigations and bandgap analysis, the carrier density of IAZO is found to be increased by > 104 times compared to that of unannealed IAZO after low temperature annealing at 200 °C in air. Photoelectron spectroscopic studies reveal that the typical intrinsic (vacancy-based native defect) or extrinsic (cation substitution) doping mechanisms are not the primary cause of the channel carrier increase. From high pressure oxidation with much enhanced reactivity of reaction gases, it is identified that the equilibrium carrier density of IAZO is much higher than those used in typical TFT channel application. The low channel carrier density tends to increase and reach the higher equilibrium carrier density in the absence of kinetic constraints. The combinatorial investigations presented herein help understand the origin of unintentional increase in channel carrier density in amorphous oxides and its effect on the operation of TFTs. The authors gratefully acknowledge the financial supports of the U.S. NSF Award No. ECCS-1931088; the Purdue Research Foundation (Grant No. 60000029); and the Improvement of Measurement Standards and Technology for Mechanical Metrology (Grant No. 20011028) by KRISS. References Reed et al. Journal of Materials Chemistry C 2020, 8 (39), 13798-13810. Nomura et al. Applied Physics Letters 2009, 95 (1), 013502. Lee et al. Thin Solid Films 2012, 520 (10), 3764-3768. Shimura et al. Thin Solid Films 2008, 516 (17), 5899-5902. Lee et al. Journal of Applied Physics 2011, 109 (6), 063702. Ide et al. physica status solidi (a) 2019, 216 (5), 1800372. Liu et al. Journal of the American Chemical Society 2010, 132 (34), 11934-11942. Lee et al. Applied Physics Letters 2014, 104 (25), 252103.
The limitless potential of ultraviolet (UV) information is fueling the development of photodetecting technology beyond color image acquisitions such as air pollution monitoring, oil spill detection, and missile tracking systems. Ideal detectors for such applications need to separately perceive UV and visible lights to maximize their functional versatility. However, traditional device structures (e.g., photodiodes and photoconductors) inevitably require expensive filters or supplementary devices to discriminate the light sources. This study aims to develop photodetectors that provide dual functionalities in a single-unit device without any filters. To this end, we propose a device configuration based on two Schottky diodes stacked antiparallel. The dual-Schottky junctions (DSJs) uniquely arrange the band structure within the device to selectively create photocurrent from the targeted wavelengths (UV/visible) of light and block the rest (visible/UV) by adjusting the bias polarity. In addition, we further demonstrate dual-spectral detection in real time by mapping UV and broad-band (UV + visible) light images in a single frame without the aid of supplementary filters or equipment. The filter-free system, capable of UV/visible discrimination, would pave the way for developing a universal and multimodal next-generation photodetector with enhanced detection rates.
The discovery of oxide electronics is of increasing importance today as one of the most promising new technologies and manufacturing processes for a variety of electronic and optoelectronic applications such as next-generation displays, batteries, solar cells, memory devices, and photodetectors[1]. The high potential use seen in oxide electronics is due primarily to their high carrier mobilities and their ability to be fabricated at low temperatures[2]. However, since the majority of oxide semiconductors are n-type oxides, current applications are limited to unipolar devices, eventually developing oxide-based bipolar devices such as p-n diodes and complementary metal-oxide semiconductors. We have contributed to a wide range of oxide semiconductors and their electronics and optoelectronic device applications. Particularly, we have demonstrated n-type oxide-based thin film transistors (TFT), integrating In2O3-based n-type oxide semiconductors from binary cation materials to ternary cation species including InZnO, InGaZnO (IGZO), and InAlZnO. We have suggested channel/metallization contact strategies to achieve stable and high TFT performance[3, 4], identified vacancy-based native defect doping mechanisms[5], suggested interfacial buffer layers to promote charge injection capability[6], and established the role of third cation species on the carrier generation and carrier transport[7]. More recently, we have reported facile manufacturing of p-type SnOx through reactive magnetron sputtering from a Sn metal target[8]. The fabricated p-SnOx was found to be devoid of metallic phase of Sn from x-ray photoelectron spectroscopy and demonstrated stable performance in a fully oxide-based p-n heterojunction together with n-InGaZnO. The oxide-based p-n junctions exhibited a high rectification ratio greater than 103 at ±3 V, a low saturation current of ~2x10-10, and a small turn-on voltage of -0.5 V. In this presentation, we review recent achievements and still remaining issues in transition metal oxide semiconductors and their device applications, in particular, bipolar applications including p-n heterostructures and complementary metal-oxide-semiconductor devices as well as single polarity devices such as TFTs and memristors. In addition, the fundamental mechanisms of carrier transport behaviors and doping mechanisms that govern the performance of these oxide-based devices will also be discussed. ACKNOWLEDGMENT This work was supported by the U.S. National Science Foundation (NSF) Award No. ECCS-1931088. S.L. and H.W.S. acknowledge the support from the Improvement of Measurement Standards and Technology for Mechanical Metrology (Grant No. 20011028) by KRISS. K.N. was supported by Basic Science Research Program (NRF-2021R11A1A01051246) through the NRF Korea funded by the Ministry of Education. REFERENCES [1] K. Nomura et al., Nature, vol. 432, no. 7016, pp. 488-492, Nov 25 2004. [2] D. C. Paine et al., Thin Solid Films, vol. 516, no. 17, pp. 5894-5898, Jul 1 2008. [3] S. Lee et al., Journal of Applied Physics, vol. 109, no. 6, p. 063702, Mar 15 2011, Art. no. 063702. [4] S. Lee et al., Applied Physics Letters, vol. 104, no. 25, p. 252103, 2014. [5] S. Lee et al., Applied Physics Letters, vol. 102, no. 5, p. 052101, Feb 4 2013, Art. no. 052101. [6] M. Liu et al., ACS Applied Electronic Materials, vol. 3, no. 6, pp. 2703-2711, 2021/06/22 2021. [7] A. Reed et al., Journal of Materials Chemistry C, 10.1039/D0TC02655G vol. 8, no. 39, pp. 13798-13810, 2020. [8] D. H. Lee et al., ACS Applied Materials & Interfaces, vol. 13, no. 46, pp. 55676-55686, 2021/11/24 2021.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.