Band bending and the apparent barrier height in scanning tunneling microscopy

Weimer, Michael; Kramar, John A.; Baldeschwieler, John D.

doi:10.1103/physrevb.39.5572

Cited by 78 publications

(39 citation statements)

References 16 publications

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“…The rise of the band bending is nearly directly proportional to the applied voltage. 21 In this case the electric field is only screened by the charge of ionized donors. In this voltage range no tunneling of electrons from the STM tip or from the semiconductor sample is possible, because the conduction band edge at the surface is above the tip's Fermi level for positive sample voltage, and the valence-band maximum at the surface is below the Fermi level of the tip for negative sample voltage.…”

Section: A Tunneling Through a Vacuum Barriermentioning

confidence: 99%

Scanning tunneling microscopy and spectroscopy of semi-insulating GaAs

et al. 2002

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We report on atomically resolved scanning tunneling microscopy images and tunneling spectra of ͑110͒ cleavage surfaces of semi-insulating GaAs without illumination at room temperature. With help of simple model calculations we extract the physical mechanisms involved in the tunneling processes from and into semi-insulating GaAs. Atomically resolved images can only be observed at negative voltages, while no tunneling into empty states is possible without illumination. This is explained, on the one hand, by the absence of a carrier inversion at the semiconductor surface without illumination under the nonequilibrium tunneling contact conditions. On the other hand, at negative voltages in the noncontact mode an accumulation at the surface occurs and leads to tunneling of electron from the valence band states into the empty tip states. This current is limited by the tunneling through the vacuum barrier and the scanning tunneling microscopy images are found to show the occupied dangling bond states above the arsenic atoms. In the point contact mode the current is limited by tunneling through the space charge region without and with illumination. The implications of the results for the investigation of low-conductivity materials by scanning tunneling microscopy are discussed.

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Section: A Tunneling Through a Vacuum Barriermentioning

confidence: 99%

Scanning tunneling microscopy and spectroscopy of semi-insulating GaAs

et al. 2002

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“…For a known bandbending the tunneling current can then be calculated using a tunneling theory for a MIS diode. [5][6][7][8][9][10]14,17 The question whether this quasi-equilibrium approach is valid for STS measurements is still controversly discussed. 5,10,[12][13][14] It was first recognized by Feenstra and Stroscio 5 that due to an extraction of the minority charge carriers, the semiconductor surface might not invert for the reverse bias situation.…”

Section: Introductionmentioning

confidence: 99%

“…However, on semiconductors with a low surface state density, such as H-terminated Si, cleaved GaAs͑110͒ or the layered materials WSe 2 and WS 2 , the situation is far more complex, since the applied tunneling voltage and the work function difference between the tip and the sample lead to an additional bandbending at the semiconductor surface and nonequilibrium effects need to be considered. [5][6][7][8][9][10][11][12][13][14] In a one-dimensional model the bandbending in a metalinsulator-semiconductor ͑MIS͒ diode was first determined by Garret and Brattain 15 and Kingston and Neustadter 16 by integrating the Poisson equation, including accumulation, depletion and inversion at the semiconductor surface. For a known bandbending the tunneling current can then be calculated using a tunneling theory for a MIS diode.…”

Section: Introductionmentioning

confidence: 99%

Tunneling spectroscopy on semiconductors with a low surface state density

Sommerhalter¹,

Matthes²,

Boneberg³

et al. 1997

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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A detailed study of tunneling spectroscopy concerning semiconductors with a low surface state density is presented. For this purpose, I -V curves under dark conditions and under illumination were measured on the ͑0001͒ van der Waals surface of a p-type WS 2 single crystal, which is known to be free of intrinsic surface states. The measurements are interpreted by an analytical one-dimensional metal-insulator-semiconductor model, which shows that the presence of the finite tunneling current has to be considered in the calculation of the tip-induced bandbending. Rectification of the dark I -V curves is explained by the absence of an inversion layer at the semiconductor surface. In contrast, the I -V curves measured for different light intensities and tip-sample separations indicate the existence of an optically induced inversion layer. Since no surface recombination needs to be considered to model these spectra, we conclude that bulk recombination, diffusion and direct tunneling of photogenerated minority charge carriers are the dominant processes for semiconductors with a low density of surface states. In contrast to the standard interpretation of tunneling spectroscopy, which can be applied to semiconductors with a high surface state density, our results clearly show that in this case the normalized differential conductivity (dI/dU)/(I/U) cannot be used to determine the energetic distribution of the local surface state density.

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“…Clearly, the tunnel currents have an exponential dependence on the tip-sample separation. 25 This accounts for the fact that under small bias conditions the current shows stronger dependence on the tip-sample separation than the one under the large bias region.…”

Section: Resultsmentioning

confidence: 95%

A reverse bias, tip-insulator-semiconductor tunnel diode model accounting for the delineation of a p/p+ junction using scanning tunneling microscopy

Lin

Jaccodine

Freund

2000

Journal of Applied Physics

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In this article, a tunneling-generation-avalanche model has been proposed to explain the reverse bias current–voltage behavior observed at a tip/air/p-type silicon junction. Based on this model, under conditions where the applied bias is more negative than the flat band voltage, the current will be dominated by generation processes, which has significant doping density dependence. Since mechanically cut tips, used in this work, can have complicated geometries, geometric effects, such as extended gates and concentration of the electrical field must be taken into account. By taking these factors into account, good agreement between theory and experiments can be achieved. Finally, in the presence of illumination, p/p+ junctions can be delineated successfully by taking advantage of the generation process. These results demonstrate that scanning tunneling microscopy can be used as a powerful tool for characterizing semiconductor devices.

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Band bending and the apparent barrier height in scanning tunneling microscopy

Cited by 78 publications

References 16 publications

Scanning tunneling microscopy and spectroscopy of semi-insulating GaAs

Scanning tunneling microscopy and spectroscopy of semi-insulating GaAs

Tunneling spectroscopy on semiconductors with a low surface state density

A reverse bias, tip-insulator-semiconductor tunnel diode model accounting for the delineation of a p/p+ junction using scanning tunneling microscopy

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