Dynamics of Charge Carriers in Silicon Nanowire Photoconductors Revealed by Photo Hall Effect Measurements

Chen, Kaixiang; Zhao, Xiaolong; Mesli, A.; He, Yongning; Dan, Yaping

doi:10.1021/acsnano.8b00004

Cited by 17 publications

(26 citation statements)

References 22 publications

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“…To verify the doping concentration and carrier mobility, we performed Hall effect measurements at single nanowire level. The details of Hall measurements can be found in our previous publications [20], [21]. The measured doping concentrations and carrier mobilities are plotted as red dots in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…After these two misplaced assumptions were corrected, we found a photoconductor intrinsically has no gain, or a small gain less than the ratio of majority to minority mobility [19]. The photogain comes from the surface depletion region in which the built-in electric field will pump the photogenerated majority carriers into the conduction channel [20]. Based on this model, we recently established an explicit photogain theory that can fit and predict the photoresponses and gain of nanoscale photodetectors [20]- [22].…”

Section: Introductionmentioning

confidence: 99%

“…The photogain comes from the surface depletion region in which the built-in electric field will pump the photogenerated majority carriers into the conduction channel [20]. Based on this model, we recently established an explicit photogain theory that can fit and predict the photoresponses and gain of nanoscale photodetectors [20]- [22]. In this work, we managed to find a large number of important device parameters at single nanowire level by a single fitting of the explicit theory to the experimental photoresponses.…”

Section: Introductionmentioning

confidence: 99%

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Rich Device Physics Found in Photoresponses of Low-Dimensional Photodetectors by Fitting With Explicit Photogain Theory

Zhang

et al. 2022

IEEE Electron Device Lett.

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In this work, we employed our newly established explicit photogain theory to probe physics in nanodevices at single device level. A single fitting of the explicit photogain theory to experimental photoresponses allows us to find important device parameters including surface depletion region width Wdep, doping concentration Na (or Nd), carrier mobility µp (or µn), minority recombination lifetime τ0 and surface recombination velocity Vsrv. These parameters are often difficult to calibrate using traditional semiconductor characterization techniques as the size of semiconductor devices scales down. The extracted parameters were verified with independent Hall effect measurements and other experiments. It shows that this technique is simple, nondestructive and accurate enough to probe the physics in nanodevices at single device level.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Rich Device Physics Found in Photoresponses of Low-Dimensional Photodetectors by Fitting With Explicit Photogain Theory

Zhang

et al. 2022

IEEE Electron Device Lett.

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“…The same number of excess majority counterparts is accumulated in the conduction channel, leading to the experimentally observed high photogain. [ 7,9 ]…”

Section: Figurementioning

confidence: 99%

“…The photoinduced variation of charge carrier concentrations can be directly measured by photo‐Hall effect measurements, from which the deduction of ∆ p and ∆ n is dependent on conductance and Hall resistance following Equation () [ 9 ]

\begin{matrix} Δ p - Δ n = \frac{L^{2}}{e μ^{2} W^{2}} (σ^{2} \frac{normald R_{H}}{normald B} - σ_{0}^{2} \frac{normald R_{H 0}}{normald B}) \end{matrix}

where R H0 and R H are Hall resistance of the sample in the dark and under light illumination, respectively. The Hall resistances linear with magnetic field in darkness and under light illumination were recorded as shown Section S4 (Supporting Information).…”

Section: Figurementioning

confidence: 99%

Explicit Gain Equations for Hybrid Graphene‐Quantum‐Dot Photodetectors

Chen

Zhang

Zang

et al. 2020

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Graphene is an attractive material for broadband photodetection but suffers from weak light absorption. Coating graphene with quantum dots can significantly enhance light absorption and create extraordinarily high photo gain. This high gain is often explained by the classical gain theory which is unfortunately an implicit function and may even be questionable. In this work, we managed to derive explicit gain equations for hybrid graphene-quantum-dot photodetectors. Due to the work function mismatch, lead sulfide (PbS) quantum dots coated on graphene will form a surface depletion region near the interface of quantum dots and graphene. Light illumination narrows down the surface depletion region, creating a photovoltage that gates the graphene. As a result, high photo gain in graphene is observed. The explicit gain equations are derived from the theoretical gate transfer characteristics of graphene and the correlation of the photovoltage with the light illumination intensity. The derived explicit gain equations fit well with the experimental data, from which physical parameters are extracted.Graphene is a zero-bandgap semimetal with extraordinarily high carrier mobility, 1, 2, 3, 4, 5 as a result of which graphene is an attractive material for broadband photodetection. Photodetectors based on graphene operating in the mid-infrared spectrum have been demonstrated in recent years. 6,7,8,9 However, due to its nature of being atomically thin, graphene suffers from weak light absorption, resulting in poor photoresponsivity. 10,11,12,13 Coating graphene with semiconducting quantum dots (QDs) can strongly enhance the light absorption and introduce an interesting high photo gain at an order of 10 8 , 14, 15, 16 several orders of magnitude larger than photodetectors based on pure semiconducting QDs (often have a photo gain of 10 2 -10 3 ). 17,18,19 The classical carrier-recycling gain mechanism is often used to explain the origin of high gain, 14,15,16 that is, the high gain originates from the photoexcited carriers circulating the circuits many times before recombination due to the long response time and short transit time. 20 However, this classical gain theory is an implicit function and may even be questionable. 21 It is implicit in that it is a function of carrier lifetime and transit time and cannot quantitively fit the light-intensitydependent photo gains. More importantly, the classical gain theory was derived on two questionable assumptions. 21,22 Firstly, the classical theory assumes no metal-semiconductor boundary confinement, which leads to the questionable conclusion that high gain can be obtained as long as the minority recombination lifetime is much longer than the transit time. After the metal-semiconductor boundary confinement is

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High‐Efficiency Silicon Nanowire Array Near Infrared Photodetectors via Length Control and SiO_x Surface Passivation

Son

Shin

Zhao

et al. 2023

Adv Materials Technologies

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Silicon (Si) nanowire (NW) array is a promising light‐trapping platform due to the strong interaction between light and nanostructure. A photodetector benefits from the improved optical absorption in the Si NW array. Although the optical absorption increases with the NW length, the large NW length is not always preferable owing to the large surface area. Here, the systematic study on the Si NW array photodetectors with varied NW lengths is investigated. It is revealed that the photodetectors with 1 µm length provide a highest responsivity of 0.65 A W−1 and a specific detectivity of 1.40 × 109 cm Hz1/2 W−1 at the wavelength of 1000 nm, including the dark current of 54 µA at 1 V. In addition, the silicon oxide (SiOx) surface passivation is introduced to induce the high photogain. As a result, the responsivity is improved by 13 times (0.55 A W−1) at 1100 nm. This work proposes high‐efficiency Si NW array photodetectors by the NW array length control and the SiOx surface passivation.

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Dynamics of Charge Carriers in Silicon Nanowire Photoconductors Revealed by Photo Hall Effect Measurements

Cited by 17 publications

References 22 publications

Rich Device Physics Found in Photoresponses of Low-Dimensional Photodetectors by Fitting With Explicit Photogain Theory

Rich Device Physics Found in Photoresponses of Low-Dimensional Photodetectors by Fitting With Explicit Photogain Theory

Explicit Gain Equations for Hybrid Graphene‐Quantum‐Dot Photodetectors

High‐Efficiency Silicon Nanowire Array Near Infrared Photodetectors via Length Control and SiO_x Surface Passivation

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Dynamics of Charge Carriers in Silicon Nanowire Photoconductors Revealed by Photo Hall Effect Measurements

Cited by 17 publications

References 22 publications

Rich Device Physics Found in Photoresponses of Low-Dimensional Photodetectors by Fitting With Explicit Photogain Theory

Rich Device Physics Found in Photoresponses of Low-Dimensional Photodetectors by Fitting With Explicit Photogain Theory

Explicit Gain Equations for Hybrid Graphene‐Quantum‐Dot Photodetectors

High‐Efficiency Silicon Nanowire Array Near Infrared Photodetectors via Length Control and SiOx Surface Passivation

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Product

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High‐Efficiency Silicon Nanowire Array Near Infrared Photodetectors via Length Control and SiO_x Surface Passivation