Conductive atomic force microscopy study of self-assembled silicon nanostructures

Bari, M. R.; Blaikie, Richard J.; Fang, F.; Markwitz, A.

doi:10.1116/1.3258147

Cited by 8 publications

(4 citation statements)

References 17 publications

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“…offers an effective way to study the conductive properties of individual QDs [6][7][8], which have already been employed on various QDs, including GeSi [9,10], GaN [11,12], InP [13], TiSi 2 [14], and so on.…”

Section: Introductionmentioning

confidence: 99%

Bias-dependent conductive characteristics of individual GeSi quantum dots studied by conductive atomic force microscopy

Wu¹,

Zhang²,

Lin³

et al. 2011

Nanotechnology

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The bias-dependent electrical characteristics of individual self-assembled GeSi quantum dots (QDs) are investigated by conductive atomic force microscopy. The results reveal that the conductive characteristics of QDs are strongly influenced by the applied bias. At low (-0.5 to - 2.0 V) and high (-2.5 to - 4.0 V) biases, the current distributions of individual GeSi QDs exhibit ring-like and disc-like characteristics respectively. The current of the QD's central part increases more quickly than that of the other parts as the bias magnitude increases. Histograms of the magnitude of the current on a number of QDs exhibit the same single-peak feature at low biases, and double- or three-peak features at high biases, where additional peaks appear at large-current locations. On the other hand, histograms of the magnitude of the current on the wetting layers exhibit the same single-peak feature for all biases. This indicates the conductive mechanism is significantly different for QDs and wetting layers. While the small-current peak of QDs can be attributed to the Fowler-Nordheim tunneling model at low biases and the Schottky emission model at high biases respectively, the large-current peak(s) may be attributed to the discrete energy levels of QDs. The results suggest the conductive mechanisms of GeSi QDs can be regulated by the applied bias.

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Section: Introductionmentioning

confidence: 99%

Bias-dependent conductive characteristics of individual GeSi quantum dots studied by conductive atomic force microscopy

Wu¹,

Zhang²,

Lin³

et al. 2011

Nanotechnology

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“…[26,27] The possible reason for the reduced SBH of black Ge is the increased density of surface states induced by RIE process, which has been observed in black Si. [28][29][30] As shown in Figure 4b, dark current of the planar and black Ge PDs covered with Al 2 O 3 was decreased to 0.124 and 0.616 mA, respectively. Although it is well known that the insertion of ultra-thin Al 2 O 3 (thickness of 1-3 nm) between n-Ge and metal leads to the reduction of SBH via Fermi level depinning, [31] overall contact resistance added by a tunneling resistance through Al 2 O 3 becomes increased when Al 2 O 3 is thicker, leading to the decreased dark current of the devices.…”

Section: Introductionmentioning

confidence: 87%

Black Germanium Photodetector Exceeds External Quantum Efficiency of 160%

Liao

Shin

et al. 2021

Adv Materials Technologies

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Inspired by the formation of black Si, [14,15] black Ge with nanospiked structures was achieved by femtosecond laser irradiation in SF 6 environment. [16] However, optical properties of the structure were not characterized. There have been intensive research efforts to fabricate black Ge by using the standard dry etching technique based on sulfur hexafluoride (SF 6 ) and chlorine (Cl 2 ) gases. [17,18] Although Pasanen et al. fabricated black Ge surface by SF 6 -based inductively coupled plasma reactive ion etching (ICP-RIE), [19] the etching process was carried out at −120 °C, resulting in substantial challenges for processing. Steglich et al. realized black Ge by using Cl 2 -based RIE at room temperature, but the process requires a longer etching time of 45 min. [18] The extremely high absorbance of black Ge reaching 99% was experimentally obtained in the 300-1600 nm wavelength range. However, more importantly, the excellent light absorption property of black Ge has not translated into optoelectronic performance of any functional devices.In this paper, we report the demonstration and comprehensive performance characterization of black Ge-based metal-semiconductor-metal (MSM) PDs. Spike-like Ge nanostructures with optimized dimension and uniformity are formed by Cl 2 -based room-temperature standard RIE process in 2 min. Black Ge surface exhibits an optical reflection as low as 1% at a wavelength range of 1000-2000 nm. The surface is covered with aluminum oxide (Al 2 O 3 ) to reduce dark current via an atomic layer deposition (ALD). The optoelectrical properties of black Ge PDs are compared to those of the Ge PDs made on planar surface to evaluate the applicability of black Ge toward light trapping at a device level. Responsivity of black Ge MSM PDs is enhanced significantly in the NIR range of 1.5-2 µm with a slight degradation of dark current. In addition, EQE of black Ge PDs not covered with Al 2 O 3 layer is as high as 161% at 1550 nm. Therefore, our black Ge fabricated by the simple RIE process exhibits outstanding potential for efficient NIR photodetection. Results and DiscussionFigure 1 illustrates the schematic fabrication process of black Ge PDs. Detailed process is provided in Method. In short, undoped Ge substrate (n-type, resistivity > 50 Ω cm) was thoroughly cleaned by acetone, isopropyl alcohol (IPA), and DI water. The dry etching was performed in Cl 2 environment for 2 min to In this work, a viable method is demonstrated to realize high-performance germanium (Ge) photodetectors (PDs) on the nanostructured Ge surface, namely black Ge, formed by chlorine (Cl 2 ) gas-based reactive ion etching at room temperature. Black Ge surface has spike-like pyramidal structures with a width and height up to 150 and 570 nm, respectively. Average reflection of black Ge is reduced to 2% at a wavelength range from 1 to 2 µm, while that of planar Ge is ≈37%. Light absorption is strongly enhanced by the significantly reduced reflection, thereby leading to an increase in responsivity of black Ge PDs. Moreover, external...

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“…The conductive Atomic Force Microscopy [4] as here the increased field has only fur ther reduced its height from 0. 28-0.…”

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confidence: 97%

Fabrication and characterization of integrated field emission diodes using self-assembled-silicon-nanostructure cathodes

Bari

Lansley

Blaikie

et al. 2010

2010 Conference on Optoelectronic and Microelectronic Materials and Devices

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CMOS process compatible in tegrated diodes using self-assembled silicon-nanostructure cathodes have been fabricated and characterized at atmos pheric pressure. The silicon nanostruc tures are atomically sharp and about 10 nm high, self-assembled on a silicon sub strate by electron beam annealing (EBA). The electrical conduction characteristics of the devices show Fowler-Nordheim field emission at high fields. A field en hancement factor, fl, of about 5x10 5 cm-1 and silicon effective work function,

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Conductive atomic force microscopy study of self-assembled silicon nanostructures

Cited by 8 publications

References 17 publications

Bias-dependent conductive characteristics of individual GeSi quantum dots studied by conductive atomic force microscopy

Bias-dependent conductive characteristics of individual GeSi quantum dots studied by conductive atomic force microscopy

Black Germanium Photodetector Exceeds External Quantum Efficiency of 160%

Fabrication and characterization of integrated field emission diodes using self-assembled-silicon-nanostructure cathodes

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