Improved Electrical Properties of Ga2O3:Sn/CIGS Hetero-Junction Photoconductor

2014 ◽  
Vol 1635 ◽  
pp. 83-88
Author(s):  
Kenji Kikuchi ◽  
Shigeyuki Imura ◽  
Kazunori Miyakawa ◽  
Hiroshi Ohtake ◽  
Misao Kubota ◽  
...  
Keyword(s):  
Thin Film ◽  
Quantum Efficiency ◽  
Repetition Rate ◽  
Dark Current ◽  
Carrier Density ◽  
High Efficiency ◽  
Visible Region ◽  
Laser Frequency ◽  
Image Sensors ◽  
High Quantum Efficiency

ABSTRACTWe examined the potential application of CuIn1-xGaxSe1-ySy (CIGS) film for visible light image sensors. CIGS chalcopyrite semiconductors, which are representative of high efficiency thin film solar cells, have both a high absorption coefficient and high quantum efficiency. However, their dark current is too high for image sensors. In this study, we applied gallium oxide (Ga2O3) as a hole-blocking layer for CIGS thin film to reduce the dark current. The dark current of this hetero-junction was 10-9 A/cm2 at less than 7 V. Moreover, an avalanche multiplication phenomenon was observed at an applied voltage of over 8 V. However, this structure had sensitivity only in the ultraviolet light region due to the much lower carrier density of the Ga2O3 layer. We therefore used a tin-doped Ga2O3 (Ga2O3:Sn) layer deposited by pulsed laser deposition (PLD) for the n-type layer to increase the carrier density. The sensitivity of the visible region was observed in the Ga2O3:Sn/CIGS hetero-junction. We also investigated the influence of the laser frequency of the PLD on the transmittance of Ga2O3:Sn and the quantum efficiency of this hetero-junction. Ga2O3:Sn film deposited at a 0.1-Hz laser repetition rate had higher transmittance than at a 10-Hz repetition rate. The Ga2O3:Sn/CIGS hetero-junction also had a higher quantum efficiency with the lower rate (50%) than with the higher rate (30%).

Electrical Properties of Ga2O3:Sn/CIGS Hetero-junction

2014 ◽  
Vol 1603 ◽  
Author(s):  
Kenji Kikuchi ◽  
Shigeyuki Imura ◽  
Kazunori Miyakawa ◽  
Misao Kubota ◽  
Eiji Ohta
Keyword(s):  
Thin Film ◽  
Visible Light ◽  
Dark Current ◽  
Carrier Density ◽  
High Speed ◽  
Depletion Region ◽  
Image Sensors ◽  
Frame Rate ◽  
Semiconductor Layer ◽  
High Quantum Efficiency

ABSTRACTThere is an increased need for highly sensitive imaging devices to develop high resolution and high speed image sensors. Incident light intensity per pixel of image sensors is getting lower because the pixel resolution and frame rate of image sensors are becoming higher. We investigated the feasibility of using a photoconductor with tin-doped gallium oxide (Ga2O3:Sn)/Cu(In,Ga)Se2 (CIGS) hetero-junction for visible light image sensors. CIGS chalcopyrite thin films have great potential for improving the sensitivity of image sensors and CIGS chalcopyrite semiconductors have both a high absorption coefficient and high quantum efficiency. Moreover, the band gap can be adjusted for visible light. We applied Ga2O3 as an n-type semiconductor layer and a hole-blocking layer to CIGS thin film to reduce the dark current. The experimental results revealed that dark current was drastically reduced due to the application of Ga2O3 thin film, and an avalanche multiplication phenomenon was observed at an applied voltage of over 6 V. However, non-doped Ga2O3/CIGS hetero-junction only had sensitivity in the ultraviolet light region because their depletion region was almost completely spread throughout the Ga2O3 layer due to the low carrier density of the Ga2O3 layer. Therefore, we used Ga2O3:Sn for the n-type layer to increase carrier density. As a result, the depletion region shifted to the CIGS film and the cells had sensitivity in all visible regions. These results indicate that Ga2O3:Sn/CIGS hetero-junction are feasible for visible light photoconductors.

Electrical Properties of Photoconductor Using Ga2O3/CuGaSe2 Heterojunction

2013 ◽  
Vol 1538 ◽  
pp. 391-395
Author(s):  
Kenji Kikuchi ◽  
Shigeyuki Imura ◽  
Kazunori Miyakawa ◽  
Misao Kubota ◽  
Eiji Ohta
Keyword(s):  
Visible Light ◽  
Dark Current ◽  
Carrier Density ◽  
Depletion Region ◽  
Image Sensors ◽  
High Quantum Efficiency ◽  
Light Region ◽  
Cigs Thin Film ◽  
Hole Blocking Layer ◽  
High Absorption Coefficient

ABSTRACTThe feasibility of using a photoconductor with a Ga2O3/CuGaSe2 heterojunction for visible light sensors was investigated. CIGS chalcopyrite semiconductors have both a high absorption coefficient and high quantum efficiency. However, their dark current is too high for image sensors. In this study, we applied gallium oxide (Ga2O3) as a hole-blocking layer for CIGS thin film to reduce the dark current. Experimental results showed that the dark current was drastically reduced, and an avalanche multiplication phenomenon was observed at an applied voltage of over 6 V. However, this structure had sensitivity only in the ultraviolet light region because its depletion region was almost completely spread in the Ga2O3 layer since the carrier density of the Ga2O3 layer was much lower than that of the CIGS layer. These results indicate that the Ga2O3/CuGaSe2 heterojunction has potential for use in visible light sensors but that we also need to increase the carrier density of the Ga2O3 layer to shift the depletion region to the CIGS film.

High-efficiency near-UV light-emitting diodes on Si substrates with InGaN/GaN/AlGaN/GaN multiple quantum wells

2020 ◽  
Vol 8 (3) ◽  
pp. 883-888 ◽  
Author(s):  
Yuan Li ◽  
Zhiheng Xing ◽  
Yulin Zheng ◽  
Xin Tang ◽  
Wentong Xie ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Quantum Efficiency ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Uv Light ◽  
Multiple Quantum ◽  
High Quantum Efficiency ◽  
Light Emitting ◽  
Si Substrates

High quantum efficiency LEDs with InGaN/GaN/AlGaN/GaN MQWs have been demonstrated. The proposed GaN interlayer barrier can not only increase the concentration and the spatial overlap of carriers, but also improve the quality of the MQWs.

A High Performance UV Photodetector from Thin Film Diamond

1995 ◽  
Vol 416 ◽  
Author(s):  
Robert D. Mckeag ◽  
Michael D. Whitfield ◽  
Simon Sm Chan ◽  
Lisa Ys Pang ◽  
Richard B. Jackman
Keyword(s):  
Thin Film ◽  
Visible Light ◽  
Quantum Efficiency ◽  
Dark Current ◽  
External Quantum Efficiency ◽  
High Performance ◽  
Uv Light ◽  
High Sensitivity ◽  
Uv Photodetector ◽  
Deep Uv

ABSTRACTThin film diamond has been used to fabricate a photodetector which displays high sensitivity to deep UV light, with an external quantum efficiency of greater than one, a dark current of less than 0.1nA and which is near ‘blind’ to visible light.

scholarly journals Image Sensors Based on Thin-film on CMOS Technology: Additional Leakage Currents due to Vertical Integration of the a-Si:H Diodes

2006 ◽  
Vol 910 ◽  
Author(s):  
Clement Miazza ◽  
N. Wyrsch ◽  
G. Choong ◽  
S. Dunand ◽  
C. Ballif ◽  
...  
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Vertical Integration ◽  
Dark Current ◽  
Cmos Technology ◽  
Image Sensors ◽  
Dark Current Density ◽  
Leakage Currents ◽  
Planar Configuration ◽  
Cmos Chip

AbstractImage sensors based on thin-film on CMOS technology (TFC) have been developed. In this approach, amorphous silicon (a-Si:H) detectors are vertically integrated on top of a CMOS readout chip so as to form monolithic image sensors. In order to reduce as far as possible the dark current density (Jdark) of the TFC sensors, we have focused on analyzing and understanding the behavior of Jdark in this type of detectors. Edge effects along the periphery and at the corners of the pixel, due to the non planar configuration of the vertically integrated photodiodes, are found to be responsible for an increase of the dark current. A new and adapted solution for the minimization of Jdark is proposed, which combines the use of a metal-i-p a-Si:H diode configuration with a deposition on top of an unpassivated CMOS chip. Values of Jdark as low as 12 pA/cm2 at a reverse polarization of V = -1 V are measured on such TFC sensors.

WO3-TiO2 Nanocomposite and its Applications: A Review

2018 ◽  
Vol 20 ◽  
pp. 1-26 ◽  
Author(s):  
Chin Wei Lai
Keyword(s):  
Thin Film ◽  
Band Gap ◽  
High Efficiency ◽  
Spectral Response ◽  
Visible Region ◽  
Charge Carriers ◽  
Nanocomposite Thin Film ◽  
Excitation Light ◽  
High Efficient ◽  
Potential Applications

Design and development of nanostructure of titanium dioxide (TiO2) assemblies has gained significant scientific interest and become the most studied material as it exhibits promising functional properties. Nevertheless, formation of TiO2 nanocomposite thin film, especially WO3-loaded TiO2 nanotubes without bundling is essential for high efficiency in many potential applications, including photocatalytic oxidation related applications, solar cell related applications, electrochromic devices and sensing related applications. Thus, this chapter aims to summarize on the development of an efficient WO3-loaded TiO2 nanotubes catalyst for the improving the performance for charge carriers transportation and extended the spectral response of TiO2 to visible spectrum. In fact, coupling TiO2 with W6+ species will lead to an additional electronic state in the band-gap of nanocomposite thin film, which in turn affect a change in the electronic and functionality of TiO2 itself. As a result, band gap narrowing effects could expand the range of excitation light to the visible region and provide sites that slow down the recombination of charge carriers. To bring more TiO2 related applications to the point of commercial readiness and viability in terms of performance and cost, substantial research on the development of high efficient nanocomposite thin film (WO3-TiO2) is necessary. In this chapter, different synthesis strategies and research findings for WO3-TiO2 nanocomposite thin film as well as its prospects in potential applications will be reviewed in detail.

A Study of Back Electrode Stacked With Low Cost Reflective Layers For High-Efficiency Thin-Film Silicon Solar Cell

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Tsung-Wei Chang ◽  
Chao-Te Liu ◽  
Wen-Hsi Lee ◽  
Yu-Jen Hsiao
Keyword(s):  
Thin Film ◽  
Solar Cell ◽  
High Performance ◽  
Silicon Solar Cell ◽  
High Efficiency ◽  
Low Cost ◽  
Visible Region ◽  
Particle Diameter ◽  
Solid Content ◽  
Thin Film Silicon

In this study, commercially available white paint is used as a pigmented dielectric reflector (PDR) in the fabrication of a low-cost back electrode stack with an Al-doped ZnO (AZO) layer for thin-film silicon solar cell applications. An initial AZO film was deposited by the radio-frequency magnetron sputtering method. In order to obtain the highest transmittance and lowest resistivity of AZO film, process parameters such as sputtering power and substrate temperature were investigated. The optimal 100-nm-thick AZO film with low resistivity and high transmittance in the visible region are 6.4 × 10−3 Ω·cm and above 80%, respectively. Using glue-like white paint doped withTiO2 nanoparticles as the PDR enhances the external quantum efficiency (EQE) of a microcrystalline silicon absorptive layer owing to the doped white particles improving Fabry–Pérot interference (FPI), which raises reflectance and scattering ability. To realize the cost down requirement, decreasing the noble metal film thickness such as a 30-nm-thick silver reflector film, and a small doping particle diameter (D50 = 135 nm) and a high solid content (20%) lead to FPI improvement and a great EQE, which is attributed to improved scattering and reflectivity because of optimum diameter (Dopt) and thicker PDR film. The results indicate that white paint can be used as a reflector coating in low-cost back-electrode structures in high-performance electronics.

Effect of Interface-Related Deep Levels on high Sensitivity of Schottky Diode Photodetector Based on Ultrathin InGaAs Film on Si

1998 ◽  
Vol 533 ◽  
Author(s):  
A. V. Kvit ◽  
M. V. Yakimov ◽  
P. L. Konstantinov ◽  
M. N. Naidenkov
Keyword(s):  
Activation Energy ◽  
Fermi Level ◽  
Quantum Efficiency ◽  
Electric Fields ◽  
Visible Region ◽  
High Sensitivity ◽  
Deep Levels ◽  
Photoluminescence Intensity ◽  
High Quantum Efficiency ◽  
Small Width

AbstractRecently, the Fermi level has been demonstrated to be pinned in GaAs semiinsulating ultrathin (<100 A) films grown at low temperatures [1]. This allows one to construct a detector with “internal” photocurrent amplification. The amplification effect compensates losses in sensitivity due to the small width of light-sensitive layer which absorbs 10 — 50 % of incident radiation. We fabricate photodetector structures with external quantum efficiency more than 1 for visible region. Photogenerated carriers in the GaAs layer are effectively separated by the built-in electric fields formed by the Schottky barrier and by the charge at the GaAs/Si interface. In this work, we show the relationships between spectral sensitivity of the metal-InGaAs/Si structures and In content. We observed the red shift in the photocurrent spectra with increasing In concentration, although photosensitivity of such structures dropped drastically. This shift demonstrates that the thin InGaAs film is actually responsible for photosensitivity. Despite the low photoluminescence intensity, the lowtemperature PL spectra indicate that band gap decreases with indium flux rising during MEE growth. The surprise was that the decrease of the film thickness caused the increase of photosensitivity. The GaAs(20 A)-InGaAs (20 A)/Si structure was the most sensitive one. We also observed high quantum efficiency in near-UV region (up to 0.8). We determined activation energy of elctron and hole traps and their concentration profiles by DLTS. The centers localized on interface between polar and nonpolar semiconductors are responsible for Fermi-level pinning in III-V semiinsulating materials and act as an electron trap with activation energy 0.59 eV. The origin of deep levels is discussed.

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