Color separation enhancement of pixn diodes by optimizing absorption regions of a-SiGe:H/a-SiC:H alloys and using a low reflective Al-doped ZnO cathode

2012 ◽  
Vol 1426 ◽  
pp. 181-186 ◽  
Author(s):  
Andreas Bablich ◽  
Krystian Watty ◽  
Christian Merfort ◽  
Markus Boehm
Keyword(s):  
Reverse Bias ◽  
Crystalline Silicon ◽  
Spectral Response ◽  
Reverse Bias Voltage ◽  
Device Structure ◽  
Band Shift ◽  
Response Characteristics ◽  
Interference Fringes ◽  
Back Reflectors ◽  
Graded Layers

ABSTRACTSecurity imaging systems working with crystalline silicon CCD or CMOS detectors are not able to distinguish colorimetrically between a large number of dangerous chemical substances, for example whitish powders [1]. In order to offer an alternative to expensive and destructive chemical methods of analysis, we developed optimized hydrogenated amorphous silicon (a-Si:H) multicolor photodiodes with different spectral response characteristics for a reliable, fast, cheap and non-destructive identification of potentially dangerous substances. Experimental optical, C-V and I-V studies were performed to explore the effect of combining linear graded a‑SiC:H-/a‑SiGe:H layers with low-reflective ZnO:Al back-contacts. Typically, a-Si:H with profiled energy gaps can be found in tandem solar cells to optimize the collection of incoming photons [2,3]. We determined the absorption coefficients of a group of a-SiC:H and a-SiGe:H graded and non-graded layers to calculate the penetration depth of photons at different energies into the device structure. Knowing the indices of absorption, refraction and extinction, it is possible to engineer diodes in such a way that accumulations of charge carriers are generated precisely at varying device depths. Common chromium back reflectors avoid a sharp falling edge of the sensitivity towards longer wavelengths and lead to interference fringes in the spectral response [4]. By combining linear graded absorption zones and ZnO:Al back contacts, we designed an optimized device with a highly precise adjustment of the spectral sensitivity reaching from 420 nm to 560 nm and reduced interference fringes at a very low reverse bias voltage of maximum -2.5 V. Similar three terminal devices allow a shift from 440 nm to 630 nm, however, at a much higher reverse bias of -11 V at 560 nm [4]. Present research efforts concentrate on the development of fast and high dynamic front illumination device structures which ensure a continuous narrow-band shift of the spectral photosensitivity and an optimum adaption to a predetermined light source-/sample measurement configuration.

Two-dimensional a-Si:H/a-SiC:H n-i-p sensor array with ITO/a-SiNx antireflection coating

2005 ◽  
Vol 862 ◽  
Author(s):  
Yu. Vygranenko ◽  
J. H. Chang ◽  
A. Nathan
Keyword(s):  
Reverse Bias ◽  
Spectral Response ◽  
Charge Trapping ◽  
Optical Excitation ◽  
Antireflection Coating ◽  
Two Dimensional ◽  
Device Structure ◽  
Response Characteristics ◽  
Photodiode Array

AbstractThis paper presents a two-dimensional a–Si:H/a-SiC:H n–i–p photodiode array with switching diode readout, developed specifically for fluorescence-based bio-assays. Both device structure and fabrication processing has enabled enhancement of the external quantum efficiency of the encapsulated device up to 80%, reduction of the photodiode leakage down to 10 pA/cm2 at -1V reverse bias, and increase of the rectification current ratio of the switching diodes up to 109. The critical fabrication issues associated with deposition of device-quality materials, tailoring of defects at the i–p interface, device patterning with dry etching, junction passivation, and contact formation will be discussed. Both sensing and switching diodes were characterized. While the observed dark current in the photodiodes at low reverse bias voltages is primarily due to carrier emission from deep states in the a–Si:H bulk, the leakage in the small switching diodes stems from peripheral defects along junction sidewalls. Optical losses in the photodiodes with ITO/a–SiNx:H antireflection coating were evaluated using numerical modeling, and the calculated transmission spectra correlated well with the spectral response characteristics. Measurements of the charge transfer time and output linearity demonstrated the efficiency of the single-switching diode readout configuration. The response of the array to optical excitation was also investigated. The observed long term retardation in the signal rise and decay at illumination levels less than 1010 photons/cm2-s can be associated with charge trapping in the undoped layer.

scholarly journals Silicon Waveguide Integrated with Germanium Photodetector for a Photonic-Integrated FBG Interrogator

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1683
Author(s):  
Hongqiang Li ◽  
Sai Zhang ◽  
Zhen Zhang ◽  
Shasha Zuo ◽  
Shanshan Zhang ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Dark Current ◽  
Reverse Bias ◽  
Spectral Response ◽  
Incident Light ◽  
Absorption Efficiency ◽  
Silicon On Insulator ◽  
Reverse Bias Voltage ◽  
Device Structure ◽  
Simulation And Optimization

We report a vertically coupled germanium (Ge) waveguide detector integrated on silicon-on-insulator waveguides and an optimized device structure through the analysis of the optical field distribution and absorption efficiency of the device. The photodetector we designed is manufactured by IMEC, and the tests show that the device has good performance. This study theoretically and experimentally explains the structure of Ge PIN and the effect of the photodetector (PD) waveguide parameters on the performance of the device. Simulation and optimization of waveguide detectors with different structures are carried out. The device’s structure, quantum efficiency, spectral response, response current, changes with incident light strength, and dark current of PIN-type Ge waveguide detector are calculated. The test results show that approximately 90% of the light is absorbed by a Ge waveguide with 20 μm Ge length and 500 nm Ge thickness. The quantum efficiency of the PD can reach 90.63%. Under the reverse bias of 1 V, 2 V and 3 V, the detector’s average responsiveness in C-band reached 1.02 A/W, 1.09 A/W and 1.16 A/W and the response time is 200 ns. The dark current is only 3.7 nA at the reverse bias voltage of −1 V. The proposed silicon-based Ge PIN PD is beneficial to the integration of the detector array for photonic integrated arrayed waveguide grating (AWG)-based fiber Bragg grating (FBG) interrogators.

Effects of a Bias Voltage During Hydrogenation on Passivation of the Defects in Polycrystalline Silicon for Solar Cells

2009 ◽  
Vol 1153 ◽  
Author(s):  
Yoji Saito ◽  
Hayato Kohata ◽  
Hideyuki Sano
Keyword(s):  
Solar Cells ◽  
Bias Voltage ◽  
Reverse Bias ◽  
Spectral Response ◽  
Short Circuit ◽  
Hydrogen Plasma ◽  
Short Circuit Current ◽  
Ir Absorption ◽  
Reverse Bias Voltage ◽  
Response Characteristics

AbstractThe short circuit current and conversion efficiency of the poly(multi)-crystalline solar cells are increased by the passivation process using hydrogen plasma. The passivation rate apparently increases at a reverse bias voltage near 0.6V during the hydrogenation process. The effects of the bias voltage on the passivation are large at the substrate temperatures between 200C and 250C. The phenomena are likely due to the existence of positively-ionized hydrogen, H+. The H+ ions can be accelerated from the surface into the bulk by the electric field with the negative bias. The possibility of the H+ ions in the bulk silicon has been predicted in the previous reports. The increase of the incorporated hydrogen is confirmed by IR absorption measurements. The enhanced diffusion of hydrogen induced by the reverse bias is supported by the results of spectral response characteristics of the hydrogenated solar cells.

Amorphous Photodiode with an Intermediate Contact for Improved Color Separation

2011 ◽  
Vol 1305 ◽  
Author(s):  
Krystian Watty ◽  
Andreas Bablich ◽  
Konstantin Seibel ◽  
Christian Merfort ◽  
Markus Boehm
Keyword(s):  
Spectral Sensitivity ◽  
Crystalline Silicon ◽  
Low Cost ◽  
Spectral Response ◽  
High Vacuum ◽  
Color Reproduction ◽  
Device Structure ◽  
External Bias ◽  
Color Separation ◽  
Color Filters

ABSTRACTMost of actual photonic devices being sensitive in the visible (VIS) spectrum are based on crystalline silicon (x-Si). The production of x-Si requires an expensive high temperature process. The color reproduction with x-Si diodes additionally requires an integration of color filters [1] to realize a shift in spectral sensitivity. This work presents an amorphous silicon (a-Si:H) photodiode with an intermediate contact for color separation without color filters. Such detectors can be produced in a low cost and low temperature PECVD process, which allows their direct deposition on a custom specific ASIC [2]. Another advantage of a-Si:H is the up to 10 times higher light absorption compared to that of x-Si in the VIS spectrum [3]. The device consists of a metal (Cr) cathode, an amorphous NIP diode structure and a TCO (Al doped ZnO) anode. The I-layer includes an interior TCO contact buried between two P-layers. The thickness of this TCO layer is about 200 nm; the P-layers have a thickness of about 10 nm. The chromium cathode is sputtered on a glass substrate in a PVD process. The amorphous layers are deposited in a multi-chamber PECVD line; the buried and top TCO contacts are sputtered in the same line continuously under high-vacuum conditions. In a first photolithography step the top anode is patterned while the buried anode is uncovered. Afterwards, the diode must be patterned again, resulting in a final Cr, NIP-a-Si:H, TCO, PIP-a-Si:H and TCO multi-layer stack.The spectral sensitivity of a common NIP diode can be shifted by external bias voltages. The spectral sensitivity at higher negative voltages overlays those of that at lower voltages and additionally shifts to longer wavelengths. The color reproduction is difficult; it can be improved by reducing the overlap of the spectral sensitivity [4]. The spectral response of the diodes presented in this work also can be shifted by the bias voltage. Furthermore, it can be split by substituting the disclosed anodes. The spectral response, using the cathode and top anode has a maximum at short wavelengths. If the diode between the interior anode and the cathode is used, the spectral sensitivity for longer wavelengths increases. Shorter wavelengths are blocked by the top part of the diode; it works like a filter. The presented device structure offers good prospects to improve color separation compared to currently existing detectors by using an additional intermediate contact.

scholarly journals Квантовый выход кремниевого лавинного фотодиода в диапазоне длин волн 120-170 nm

2020 ◽  
Vol 90 (8) ◽  
pp. 1386
Author(s):  
П.Н. Аруев ◽  
В.П. Белик ◽  
В.В. Забродский ◽  
Е.М. Круглов ◽  
А.В. Николаев ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Wavelength Range ◽  
Bias Voltage ◽  
Reverse Bias ◽  
Avalanche Photodiode ◽  
Reverse Bias Voltage ◽  
External Quantum Yield

The external quantum yield of silicon avalanche photodiode in the wavelength range of 120-170 nm was performed. It was shown that the engineered avalanche photodiode has the external quantum yield of 24-150 electron/proton under reverse bias voltage of 230-345 V, respectively. The testing of worked out avalanche photodiode by means of pulse flash of 280 and 340 nm wavelength demonstrates the speed, corresponding to the bandwidth not less than 25 MHz.

Optical detected magnetic resonance of nitrogen-vacancy centers in vertical diamond Schottky diode

2021 ◽  
Author(s):  
Muhammad Hafiz bin Abu Bakar ◽  
Aboulaye Traore ◽  
Junjie Guo ◽  
Toshiharu MAKINO ◽  
Masahiko Ogura ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Bias Voltage ◽  
Schottky Diode ◽  
Stark Effect ◽  
Reverse Bias ◽  
Nitrogen Vacancy ◽  
Reverse Bias Voltage ◽  
Zero Phonon Line ◽  
Optically Detected ◽  
Nv Centers

Abstract Diamond solid-state devices are very attractive to electrically control the charge state of Nitrogen-Vacancy (NV) centers. In this work, Vertical p-type Diamond Schottky Diode (VDSDs) is introduced as a platform to electrically control the interconversion between the neutral charge NV (NV0) and negatively charged NV (NV-) centers. The photoluminescence (PL) of NV centers generated by ion-implantation in VDSDs shows the increase of NV- Zero Phonon Line (ZPL) and phonon sideband (PBS) intensities with the reverse voltage, whereas the NV0 ZPL intensity decreases. Thus, NV centers embedded into VDSDs are converted into NV- under reverse bias voltage. Moreover, the optically detected magnetic resonance (ODMR) of NV- exhibits an increase in the ODMR contrast with the reverse bias voltage and splitting of the resonance dips. Since no magnetic is applied, such a dip splitting in ODMR spectrum is ascribed the Stark effect induced by the interaction of NV- with the electric field existing within the depletion region of VDSDs.

scholarly journals Light trapping in hydrogenated amorphous and nano-crystalline silicon thin film solar cells

2009 ◽  
Vol 1153 ◽  
Author(s):  
Jeffrey Yang ◽  
Baojie Yan ◽  
Guozhen Yue ◽  
Subhendu Guha
Keyword(s):  
Stainless Steel ◽  
Solar Cells ◽  
Triple Junction ◽  
Crystalline Silicon ◽  
Light Trapping ◽  
Nano Crystalline ◽  
Back Reflectors ◽  
Back Reflector ◽  
Junction Structure ◽  
Hydrogenated Amorphous

AbstractLight trapping effect in hydrogenated amorphous silicon-germanium alloy (a-SiGe:H) and nano-crystalline silicon (nc-Si:H) thin film solar cells deposited on stainless steel substrates with various back reflectors is reviewed. Structural and optical properties of the Ag/ZnO back reflectors are systematically characterized and correlated to solar cell performance, especially the enhancement in photocurrent. The light trapping method used in our current production lines employing an a-Si:H/a-SiGe:H/a-SiGe:H triple-junction structure consists of a bi-layer of Al/ZnO back reflector with relatively thin Al and ZnO layers. Such Al/ZnO back reflectors enhance the short-circuit current density, Jsc, by ˜20% compared to bare stainless steel. In the laboratory, we use Ag/ZnO back reflector for higher Jsc and efficiency. The gain in Jsc is about ˜30% for an a-SiGe:H single-junction cell used in the bottom cell of a multi-junction structure. In recent years, we have also worked on the optimization of Ag/ZnO back reflectors for nano-crystalline silicon (nc-Si:H) solar cells. We have carried out a systematic study on the effect of texture for Ag and ZnO. We found that for a thin ZnO layer, a textured Ag layer is necessary to increase Jsc, even though the parasitic loss is higher at the Ag and ZnO interface due to the textured Ag. However, a flat Ag can be used for a thick ZnO to reduce the parasitic loss, while the light scattering is provided by the textured ZnO. The gain in Jsc for nc-Si:H solar cells on Ag/ZnO back reflectors is in the range of ˜60-75% compared to cells deposited on bare stainless steel, which is much larger than the enhancement observed for a-SiGe:H cells. The highest total current density achieved in an a-Si:H/a-SiGe:H/nc-Si:H triple-junction structure on Ag/ZnO back reflector is 28.6 mA/cm2, while it is 26.9 mA/cm2 for a high efficiency a-Si:H/a-SiGe:H/a-SiGe:H triple-junction cell.

Photoresponse Linearity of a-Si:H Imaging Pixels

1993 ◽  
Vol 297 ◽  
Author(s):  
J. Yorkston ◽  
L.E. Antonuk ◽  
W. Huang ◽  
R.A. Street
Keyword(s):  
Amorphous Silicon ◽  
Bias Voltage ◽  
Linear Response ◽  
Reverse Bias ◽  
Reverse Bias Voltage ◽  
Imaging Arrays ◽  
Low Contrast ◽  
X Ray

Amorphous silicon imaging arrays with ∼3×105 pixels have recently been developed and x-ray images of low contrast anatomical phantoms have been demonstrated. This paper reports on the linearity of response of these a-Si:H imaging pixels as a function of reverse bias voltage. The fraction of the imaging pixel's full signal range that maintains a linear response has been found to increase with increasing voltage.

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