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Title: Detecting Fermi-level shifts by Auger electron spectroscopy in Si and GaAs

Abstract

In this study, changes in surface Fermi-level of Si and GaAs, caused by doping and cleaning, are investigated by Auger electron spectroscopy. Based on the Auger voltage contrast, we compared the Auger transition peak energy but with higher accuracy by using a more accurate analyzer and an improved peak position determination method. For silicon, a peak shift as large as 0.46 eV was detected when comparing a cleaned p-type and n-type wafer, which corresponds rather well with the theoretical difference in Fermi-levels. If no cleaning was applied, the peak position did not differ significantly for both wafer types, indicating Fermi-level pinning in the band gap. For GaAs, peak shifts were detected after cleaning with HF and (NH 4) 2S-solutions in an inert atmosphere (N 2-gas). Although the (NH 4) 2S-cleaning in N 2 is very efficient in removing the oxygen from the surface, the observed Ga- and As-peak shifts are smaller than those obtained after the HF-cleaning. It is shown that the magnitude of the shift is related to the surface composition. After Si-deposition on the (NH 4) 2S-cleaned surface, the Fermi-level shifts back to a similar position as observed for an as-received wafer, indicating that this combination is notmore » successful in unpinning the Fermi-level of GaAs.« less

Authors:
 [1];  [1];  [1];  [2];  [3];  [4];  [1];  [1]
  1. KU Leuven, Heverlee (Belgium)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. IBM Research Zurich, Ruschlikon (Switzerland)
  4. KU Leuven, Heverlee (Belgium); IMEC vzw, Heverlee (Belgium)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1418021
Report Number(s):
PNNL-SA-130366
Journal ID: ISSN 0169-4332; PII: S0169433218300801
Grant/Contract Number:
AC05-76RL01830
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Applied Surface Science
Additional Journal Information:
Journal Volume: 440; Journal ID: ISSN 0169-4332
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; Auger electron spectroscopy; semiconductor surface; Fermi level shifts; surface cleaning

Citation Formats

Debehets, J., Homm, P., Menghini, M., Chambers, S. A., Marchiori, C., Heyns, M., Locquet, J. P., and Seo, J. W. Detecting Fermi-level shifts by Auger electron spectroscopy in Si and GaAs. United States: N. p., 2018. Web. doi:10.1016/J.APSUSC.2018.01.079.
Debehets, J., Homm, P., Menghini, M., Chambers, S. A., Marchiori, C., Heyns, M., Locquet, J. P., & Seo, J. W. Detecting Fermi-level shifts by Auger electron spectroscopy in Si and GaAs. United States. doi:10.1016/J.APSUSC.2018.01.079.
Debehets, J., Homm, P., Menghini, M., Chambers, S. A., Marchiori, C., Heyns, M., Locquet, J. P., and Seo, J. W. Fri . "Detecting Fermi-level shifts by Auger electron spectroscopy in Si and GaAs". United States. doi:10.1016/J.APSUSC.2018.01.079.
@article{osti_1418021,
title = {Detecting Fermi-level shifts by Auger electron spectroscopy in Si and GaAs},
author = {Debehets, J. and Homm, P. and Menghini, M. and Chambers, S. A. and Marchiori, C. and Heyns, M. and Locquet, J. P. and Seo, J. W.},
abstractNote = {In this study, changes in surface Fermi-level of Si and GaAs, caused by doping and cleaning, are investigated by Auger electron spectroscopy. Based on the Auger voltage contrast, we compared the Auger transition peak energy but with higher accuracy by using a more accurate analyzer and an improved peak position determination method. For silicon, a peak shift as large as 0.46 eV was detected when comparing a cleaned p-type and n-type wafer, which corresponds rather well with the theoretical difference in Fermi-levels. If no cleaning was applied, the peak position did not differ significantly for both wafer types, indicating Fermi-level pinning in the band gap. For GaAs, peak shifts were detected after cleaning with HF and (NH4)2S-solutions in an inert atmosphere (N2-gas). Although the (NH4)2S-cleaning in N2 is very efficient in removing the oxygen from the surface, the observed Ga- and As-peak shifts are smaller than those obtained after the HF-cleaning. It is shown that the magnitude of the shift is related to the surface composition. After Si-deposition on the (NH4)2S-cleaned surface, the Fermi-level shifts back to a similar position as observed for an as-received wafer, indicating that this combination is not successful in unpinning the Fermi-level of GaAs.},
doi = {10.1016/J.APSUSC.2018.01.079},
journal = {Applied Surface Science},
number = ,
volume = 440,
place = {United States},
year = {Fri Jan 12 00:00:00 EST 2018},
month = {Fri Jan 12 00:00:00 EST 2018}
}

Journal Article:
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  • The use of Auger electron spectroscopy (AES) combined with in situ sputter etching for revealing the metallurgy of the metal-semiconductor interface is presented. The physical basis, measurement techniques, and data interpretation for Auger analysis of thin-film structures are briefly reviewed. Results of a detailed study of an alloyed multilayered contact (Ni/Au-Ge) on n-type epitaxial GaAs are summarized to illustrate how electrical and metallurgical contact properties can be correlated using AES. In addition, the results of a study of the growth kinetics and chemical phase identification of palladium silicide on single-crystal Si is given, as well as the initial results ofmore » a study of aluminum-palladium silicide interaction at elevated temperature. (auth)« less
  • The interface structure of thin overlayers of GaAs grown using molecular-beam epitaxy techniques on on-axis Si(100), Si(111), and Ge(111) substrates has been studied using photoemission core-level spectroscopy. Results for As and Ga overlayers are also reported and are utilized to interpret the results for GaAs growth. The interface bonding is found to be the same for growth using predeposition of Ga as for predeposition of As. For GaAs on Si(111), the bonding at the interface is found to consist predominantly of Si-As bonds. We also find strong evidence of island formation before the completion of the first GaAs bilayer. Themore » total area between islands can be reduced either by faster deposition rates or by using a Ga prelayer. For GaAs on Si(100), bonding takes place to both Ga and As but with fewer Si-Ga bonds than Si-As bonds. The tendency to island formation is less than for the Si(111) case. These results are compared with earlier data for As interaction with off-axis Si(100) surfaces to explain the absence of antiphase domains in GaAs grown on off-axis (100) substrates. Roughly equal numbers of Ge-As and Ge-Ga bonds were found for GaAs on Ge(111), and this result is interpreted as indicating that Ge interdiffuses more rapidly into GaAs than does Si.« less
  • Electron stimulated desorption, Auger line shape analysis, and electron loss spectroscopy measurements are reported for the electron activated stepwise oxidation and nitridation of the Si(111) surface. In ESD it is found that appreciable levels of surface hydrogen can be present which can lead to hydroxyl formation upon oxidation. The hydroxyl rich films are unstable in an electron beam, while surfaces oxidized with activated oxygen, where no OH is formed, are much more stable. The nitrided films are always stable in the electron beam even though there too hydrogen is always found. On the OH-free oxide, ESD shows two chemically distinctmore » O species, one thought to be SiO/sub 2/ and the other adsorbed O/sub 2/ or a chemical intermediate. The Si(L/sub 23/VV) Auger spectra for both the oxide and nitride are treated by background subtraction, integration, deconvolution, and subtraction of the elemental part of the spectrum, as a function of reaction time over a well controlled series of reaction steps. The Auger spectra for both oxide and nitride films suggest that in the earliest stages of reaction, the reacted film is made up of low coordination intermediates which gradually evolve to the stoichiometric compound as the coordination increases. In loss spectroscopy, both the Si(L/sub 23/) core loss and the near elastic loss were measured. The L/sub 23/ core loss shows the same gradual evolution to the oxide seen in the Auger results, with an intermediate oxidation state dominating in the early stages of reaction. The near elastic loss spectra, by contrast, quickly saturate in the early stages of reaction to the final oxide spectrum which is characterized by features both of the full oxide and a suboxide. Similar results are found for the nitride.« less
  • Work function, photoemission yield, and Auger electron spectra were measured on (001) p-type GaAs during negative electron affinity (NEA) surface preparation, surface degradation, and heating processes. The emission current sensitively depends on work function change and its dependence allows us to determine that the shape of the vacuum barrier was close to double triangular. Regarding the NEA surface degradation during photoemission, we discuss the importance of residual gas components the oxygen and hydrogen. We also found that gentle annealing (≤100 °C) of aged photocathodes results in a lower work function and may offer a patch to reverse the performance degradation.
  • The blueshift results from the higher H/Si ratio; the invariant yield is believed to be limited by the density of dangling bonds at the SiO[sub [ital x]]H[sub [ital y]]/Si interface which is apparently unaffected by the treatments. It is therefore believed that the PL is at least partially due to SiH[sub [ital x]] or SiO[sub [ital x]]H[sub [ital y]] complexes on the crystallite and column surfaces, which are similar to those found at the surface of some H-rich [ital a]-Si:H. Size effects, however, cannot be ruled out. In contrast to films etched from 7 to 20 [Omega] cm wafers, [lambda][submore » max] of those prepared from 1 to 2 [Omega] cm substrates was consistently [similar to]7000 A after a brief exposure to air. While [eta] exhibited a complex dependence on the O[sub 2] RIE power, [lambda][sub max] was unchanged by either O[sub 2] or H[sub 2] plasmas. The emission from heavily doped [similar to]0.02 [Omega] cm films was usually undetectable. However, H[sub 2] RIE resulted in observable PL.« less