Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
Browse
4 results
Search Results
Conference Object Citation - WoS: 1Citation - Scopus: 1Minority Carrier Properties of Microcrystalline Silicon Thin Films Grown by Hw-Cvd and Vhf-Pecvd Techniques(National Institute of Optoelectronics, 2005) Okur, Salih; Göktaş, Oktay; Güneş, Mehmet; Finger, Friedhelm; Carius, ReinhardOpto-electronic properties of μc-Si:H films prepared by hot-wire/catalytic chemical vapor deposition (HWCVD) and very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) techniques with various silane concentrations (SC) have been investigated using Raman spectroscopy, the steady-state photocarrier grating technique (SSPG), and the steady-state photoconductivity (SSPC). A correlation between the minority carrier transport properties and the microstructure has been found, using the dependence of the diffusion length (Ld) on the SC and Raman intensity ratio (I c RS) representing crystalline volume fractions. I C RS changes from 0.22 to 0.77. Ld increases with increasing Ic RS. It peaks around 0.5 with a maximum value of 270 nm, then decreases. Similar dependences of Ld on I C RS were obtained for films prepared by both HWCVD and VHF-PECVD. However, the grating quality factor measured on highly crystalline HWCVD films is substantially smaller than that found for VHF-PECVD films, indicating a relatively higher surface roughness present in the highly crystalline HWCVD films.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.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