Laser and voltage manipulation of bistable Si dopants in the GaAs (110) surface

Smakman, EP Erwin; Bree, van J Joost; Koenraad, PM Paul

doi:10.1103/physrevb.87.085414

Cited by 10 publications

(11 citation statements)

References 22 publications

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“…Previous studies 5 27 have shown that under dark conditions bistable charging processes of doping atoms have to be taken into account. Assuming that these processes define the noise level of the spectra without optical excitation, our results suggest that the presence of free electron–hole pairs suppresses this charge switching in the photoexcited case 9 26 . We like to point out that the decrease in noise in comparison to the noise under dark conditions is not the result of a simple decrease of the SCR.…”

Section: Resultsmentioning

confidence: 78%

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Controlling the screening process of a nanoscaled space charge region by minority carriers

2016

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The miniaturization of future electronic devices is intimately connected to the ability to control electric fields on the atomic scale. In a nanoscopic system defined by a limited number of charges, the combined dynamics of bound and free charges become important. Here we present a model system based on the electrostatic interaction between a metallic tip of a scanning tunnelling microscope and a GaAs(110) semiconductor surface. The system is driven out of equilibrium by optical excitation, which provides ambipolar free charge carriers, and by an optically induced unipolar tunnel current. This combination enables the active control of the density and spatial distribution of free and bound charge in the space-charge region, that is, modifying the screening processes. Temporal fluctuations of single dopants are modified, meaning we are able to control the noise of the system. It is found that free charge carriers suppress the noise level in field-controlled, nanoscopic systems.

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Section: Resultsmentioning

confidence: 78%

“…For regime II, σ RMS increases. We attribute this to a non-equilibrium charging and discharging process of dopants 4 5 9 26 inside the SCR ( Fig. 1a,d ) due to the carrier injection.…”

Section: Resultsmentioning

confidence: 99%

Controlling the screening process of a nanoscaled space charge region by minority carriers

2016

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“…Recently, bistable behavior of Si atoms in the (110) surface layer of GaAs was observed during scanning with a STM tip [15,16]. Only and all the Si dopants in the surface layer exhibit this behavior; the dopants below the surface do not.…”

mentioning

confidence: 99%

“…The Si charge state is nonvolatile at low temperatures, which enables the storage of information [16]. For memory operation, three separate conditions need to be distinguished: (a) setting the system to Si − i , (b) setting it to Si + d , and (c) detecting the charge state.…”

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confidence: 99%

Tunable switching dynamics of a single Si dopant inGaAs(110)

et al. 2014

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The dynamic behavior of single bistable Si dopants in the GaAs (110) surface, which switch between a positive and a negative charge configuration, was investigated using a scanning tunneling microscope (STM) and noise analysis electronics. The dopant atom switching frequency shows a clear dependence on the bias voltage and tunneling current, because these parameters influence the escape and capture processes of electrons. Our physical model for these processes, taking into account the relevant tunneling barriers, matches well with the experimental data. By choosing the appropriate tunneling conditions, we show that a single dopant can be employed as a memory element. The STM tip serves both as an electrical gate to write and as a probe to read the information stored on a single Si atom.

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“…For regime II, σ RMS increases. We attribute this to a nonequilibrium charging and discharging process of dopants 19,87,91,96 inside the SCR due to the carrier injection. By disturbing the hole density at the surface by valence band tunnelling I V drives the SCR in metastable configurations.…”

Section: Noise Analysis Of the Nanoscaled Space Charge Regionmentioning

confidence: 97%

Optical Excitation in Scanning Tunneling Microscopy: From Surface Photovoltages to Charge Dynamics oin the Atomic Scale

Kloth¹

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In this thesis, the successful implementation of optical excitation for time-resolved Scanning Tunneling Microscopy (STM) is presented. The fruitful combination of these two experimental methods allows investigating photo-induced dynamic processes on the nanosecond time scale with atomic resolution. The optical setup provides a great versatility regarding the adjustment of excitation parameters such as optical pulse height, pulse width or pulse repetition rate to the experimental needs. Moreover, for the first time, it is possible to disentangle and quantify thermally induced effects, e.g. thermal expansion of the STM tip, from the originally inquired signals, resulting from photo-triggered charge dynamics at the sample surface.Using continuous wave optical illumination at the Gallium-Arsenide(110) (GaAs) surface, it is proven in this thesis, that the presence of excited holes, accumulating in the tip-induced Space Charge Region (SCR) beneath the STM tip not only creates a Surface Photovoltage (SPV) but also opens an additional tunneling channel. Current dependent studies show that this extra tunneling process exhibits a high impact on the charge concentration at the surface. Assuming a steady state between charge generation via optical excitation and charge annihilation via the tunneling process, parameters such as the diffusional or field driven transport rate towards the surface are determined.The build-up and relaxation of an SPV is connected to various microscopic processes, e.g., charge transport or carrier recombination. With pulsed optical excitation, these mechanisms can be probed and disentangled. Whereas for low tunnel rates the decay of the system after optical excitation is mainly determined by the charge annihilation via the tunneling process, for high rates the recharging of dopants becomes visible. Studies of this ionization process for donors, positioned at different depths beneath the surface, reveal a significant local inhomogeneity. By applying a field driven ionization mechanism, it turns out, that the dopants cannot be treated independently from each other. Instead, the ionization dynamics have to be treated as an interacting network of coupled, locally fixed and randomly distributed charge centers.

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Laser and voltage manipulation of bistable Si dopants in the GaAs (110) surface

Cited by 10 publications

References 22 publications

Controlling the screening process of a nanoscaled space charge region by minority carriers

Controlling the screening process of a nanoscaled space charge region by minority carriers

Tunable switching dynamics of a single Si dopant inGaAs(110)

Optical Excitation in Scanning Tunneling Microscopy: From Surface Photovoltages to Charge Dynamics oin the Atomic Scale

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