Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 4Citation - Scopus: 5Conductance Fluctuations in Undoped Hydrogenated Amorphous Silicon-Germanium Alloy Thin Films(Elsevier Ltd., 2002) Güneş, Mehmet; Johanson, Robert E.; Kasap, Safa O.; Yang, Jeffrey C.; Guha, SubhenduWe report coplanar conductance fluctuations of device quality, undoped hydrogenated amorphous silicon-germanium alloy thin films (a-SiGe:H) measured from 430 to 490 K. The a-SiGe:H alloys produce noise power spectra similar to coplanar undoped a-Si:H films in the same temperature range. The noise power spectrum S(n) does not fit a single 1/fα power law but rather has two distinct regions, each accurately fitted by a power law, but with different slopes. The low frequency slope α1 is similar to that observed in undoped a-Si:H films varying from 1.30 to 1.46 for different Ge concentrations and shows a slight temperature dependence. At higher frequencies, the slope α2 is less than unity and temperature independent but depends on the Ge content of the film. α2 decreases from 0.60 for no Ge (pure a-Si:H) to 0.15 for 40 at.% Ge. The noise power at lower frequencies increases and at higher frequencies decreases substantially as the temperature increases from 430 to 490 K. We infer that similar noise mechanisms are operating in undoped a-SiGe:H and a-Si:H films but that the Ge content is influencing the noise, particularly the slope at higher frequencies. In addition, the noise has the expected quadratic dependence on bias current and obeys Gaussian statistics.Conference Object Citation - WoS: 1Citation - Scopus: 1Conductance Fluctuations in Vhf-Pecvd Grown Hydrogenated Microcrystalline Silicon Thin Films(Springer Verlag, 2003) Güneş, Mehmet; Johanson, Robert E.; Kasap, Safa O.; Finger, Friedhelm; Lambertz, AndreasCoplanar conductance fluctuations or excess noise of undoped hydrogenated microcrystal-line silicon (μc-Si : H) thin films grown by VHF-PECVD from silane-hydrogen mixtures with silane concentrations from 2% to 6% have been studied between room temperature and 470 K. We report that undoped μc-Si : H thin films show similar noise-power spectra to those of undoped a-Si : H films in a coplanar sample geometry. At lower temperatures, the noise with the slope α = 0.60 ± 0.07 and at higher temperatures, the noise with the slope α close to unity dominate the spectrum. The noise magnitude decreases with decreasing silane concentration and becomes strongly temperature dependent with increased crystal unity.Conference Object Citation - WoS: 1Citation - Scopus: 2Conductance Fluctuations in A-Si:h: Effects of Alloying and Device Structure(Springer Verlag, 2003) Kasap, Safa O.; Güneş, Mehmet; Johanson, Robert E.; Wang, Q.; Yang, Jeffrey; Guha, SubhenduWe present measurements of conductance noise in undoped a-Si:H and a-SiGe: H thin films in both a transverse and coplanar electrode geometry. For a-Si:H with coplanar electrodes, the noise spectrum is not a pure f-α power law but consists of two linear regions with different slope parameters α. The spectral shape and its temperature dependence are similar for all samples, regardless of the growth technique. Adding Ge results in qualitatively similar spectra; however, α at high frequencies and the temperature dependence are altered. For both a-Si:H and a-SiGe:H with transverse electrodes, the noise spectra are pure f-α power laws, and α decreases with the Ge content.Article Citation - WoS: 10Citation - Scopus: 71/F Noise in Doped and Undoped Amorphous Silicon(Elsevier Ltd., 2000) Johanson, Robert E.; Güneş, Mehmet; Kasap, Safa O.We measured the spectrum of conductance fluctuations in n-type, p-type, and undoped hydrogenated amorphous silicon (a-Si:H) as a function of temperature. In general, the spectra can be fit to a power law, 1/fα, although in the p-type and undoped samples deviations from a strict power law occur. For n-type and p-type samples, the noise magnitude increases with temperature by approximately a factor of 5 from 295 to 450 K. The slope parameter, α, also increases with temperature in the p-type samples from near unity to 1.4 but not in the n-type sample where it remains near 1.05 independent of temperature. The undoped sample could be measured only over a limited range of elevated temperatures, but α does trend larger. The undoped and lightly doped material have similar noise levels but larger p-type doping reduces the noise by two orders of magnitude. Correlation measurements indicate the 1/f noise is Gaussian for all samples. However, intermittent random-telegraph noise is observed in n-type material.Article Citation - WoS: 4Citation - Scopus: 4Conductance Fluctuations in Undoped Intrinsic Hydrogenated Amorphous Silicon Films Prepared Using Several Deposition Techniques(Elsevier Ltd., 2000) Güneş, Mehmet; Johanson, Robert E.; Kasap, Safa O.Coplanar conductance fluctuations in a range of device quality undoped hydrogenated amorphous silicon (a-Si:H) films prepared using different deposition systems were measured in the temperature range of 440-505 K for frequencies from 2 Hz to 3 kHz. The 1/fa type noise spectra had two different power law dependencies, one at lower frequencies with slope α1 close to unity and a second region at higher frequencies with slope α2 around 0.60. The noise power density decreases with increasing temperature in the high frequency region, but only increases much less with temperature at low frequencies. The results indicate that the noise in undoped intrinsic a-Si:H films is due to two independent noise mechanisms operating simultaneously