Fluorinated amorphous silicon-germanium alloys deposited from disilane-germane mixture

Guha, S.; Payson, J. S.; Agarwal, Samarth; Ovshinsky, Stanford R.

doi:10.1016/0022-3093(87)90349-8

Cited by 72 publications

(21 citation statements)

References 3 publications

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“…5 These alloys are used because of their availability to the authors, and their properties are representative of what is typically observed. 1,46 Subsequent works on a-Si 1Ϫx Ge x :H, which have yielded moderate improvements in optoelectronic properties compared to this earlier set, 20,21,24,26,47 do not affect the conclusions drawn from such a comparison.…”

Section: Introductionmentioning

confidence: 86%

High performance glow discharge a-Si1−xGex:H of large x

Wickboldt

Pang

Paul

et al. 1997

Journal of Applied Physics

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Radio frequency glow discharge chemical vapor deposition has been used to deposit thin films of a-Si1−xGex:H which possess optoelectronic properties that are greatly improved over any yet reported in the range of x⩾0.6. These films were deposited on the cathode (cathodic deposition) of an rf discharge. Their properties are assessed using a large variety of measurements and by comparison to the properties of alloys conventionally prepared on the anode (anodic deposition). Steady state photoconductivity measurements yield a quantum-efficiency-mobility-lifetime product, ημτ, of (1–3)×10−7 cm2 V−1 for 1.00⩾x⩾0.75 and (6–10)×10−8 cm2 V−1 for 0.75⩾x⩾0.50, and photocarrier grating measurements yield ambipolar diffusion lengths several times greater than previously obtained for alloys of large x. It is confirmed that the improvements in phototransport are not due to a shift in the Fermi level. In fact, results of recent measurements on lightly doped samples strongly suggest that for these cathodic alloys neither photocarrier is dominant [(μτ)e≈(μτ)h]. The improvements are attributed in large part to the reduction of long range structural heterogeneity observed in x-ray scattering and electron microscopy, and partly to the reduction in midgap state density. In spite of the superior properties, an assessment of the data of the cathodic alloys suggests that alloying introduces mechanisms detrimental to transport which are not present in a-Si:H or a-Ge:H. The Urbach tail width is 42±2 meV for cathodic a-Ge:H and 45±2 meV for cathodic a-Si1−xGex:H and is constant with x. From differences in the band edges and tails we infer that the atomic bond ordering is different between the cathodic and anodic alloys. For a given composition the cathodic alloys have roughly an order of magnitude lower midgap state density than do the anodic alloys, and both midgap densities increase exponentially with x, consistent with defect creation models from which the lower midgap density can be attributed to a larger band gap and decreased valence band tail width. A photoluminescence peak is observed with an intensity roughly an order of magnitude greater than for the anodic alloys, and a significantly different peak energy. Section VII E provides an overview of the results and conclusions. The improved properties of these alloys have significant implications for current and future device applications.

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Section: Introductionmentioning

confidence: 86%

High performance glow discharge a-Si1−xGex:H of large x

Wickboldt

Pang

Paul

et al. 1997

Journal of Applied Physics

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“…Guha et al have achieved an initial efficiency of 14.6% by a multi-gap amorphous silicon based solar cell in 1997 [1]. Hydrogenated amorphous silicon germanium (a-Si 1−x Ge x :H) has proved to be a promising material for the low-bandgap cell application in the multi-junction structure [2]. The composition of a-Si 1−x Ge x :H material affects its optoelectronic properties significantly.…”

Section: Introductionmentioning

confidence: 99%

Improvement of a-Si1−xGex:H single-junction thin-film solar cell performance by bandgap profiling techniques

Hsu

Tsai

2012

Journal of Non-Crystalline Solids

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“…Contrarily, the density of deep defects in the bandgap increases with increased Ge alloying which finally degrades the lifetime of photogenerated carriers [3][4][5]. Even though earlier studies reported negligible Staebler-Wronski effect (SWE) in a-SiGe:H mainly due to poor material quality available at those times [6,7], high quality alloy films prepared after improved deposition systems exhibited a substantial SWE under light soaking similar to that intrinsic to pure a-Si:H [8][9][10][11][12][13][14][15][16]. For this reason, investigations of the light induced defect creation as well as native defects in the alloy as a function of Ge content has become an important issue to be understood and resolved both scientifically and technologically.…”

Section: Introductionmentioning

confidence: 94%

“…For this reason, investigations of the light induced defect creation as well as native defects in the alloy as a function of Ge content has become an important issue to be understood and resolved both scientifically and technologically. As compared to the research undertaken during the last three decades on the SWE seen in pure a-Si:H [17], only a small number of studies have been reported for the native and light induced defects in a-SiGe:H alloys [8][9][10][11][12][13][14][15][16]. Fundamental investigations of these defects have been carried out using electron spin resonance (ESR) [4,5,10], steady-state photoconductivity (SSPC) [8,12,18], modulated photoconductivity (MPC) [19,20], drive level capacitance profiling (DLCP) [21], and sub-bandgap absorption methods [3,8,18,[21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

The effects of native and light induced defects on optoelectronic properties of hydrogenated amorphous silicon–germanium (a-SiGe:H) alloy thin films

Güneş

Yavas

Klomfass

et al. 2009

J Mater Sci: Mater Electron

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Effects of native and light induced defects states in hydrogenated amorphous silicon-germanium alloy thin films with different Ge concentrations have been investigated by using steady-state photoconductivity, dual beam photoconductivity (DBP), transmission spectroscopy and photothermal deflection spectroscopy (PDS) techniques. In the annealed state, sub-bandgap absorption spectra obtained from both PDS and DBP overlap very well at energies above 1.4 eV. However, differences in a (hm) spectrum exist in the lower energy part of absorption spectrum. The a (hm) value measured at 1.0 eV is the lowest for 10% Ge sample and increases gradually as Ge content of the sample increases. In the light soaked state, time dependence of photoconductivity decay obeys to t -x power law, where x changes from 0.30 to 0.60 for samples with low Ge content and 0.05-0.1 for samples with high Ge content. Correspondingly, the increase of the sub-bandgap absorption coefficient at lower energies obeys to t y power law, where y values are lower than the x value of the same sample. It can be inferred that sub-bandgap absorption and photoconductivity measurements are not controlled by the same set of defects created in the bandgap of alloys.

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Fluorinated amorphous silicon-germanium alloys deposited from disilane-germane mixture

Cited by 72 publications

References 3 publications

High performance glow discharge a-Si1−xGex:H of large x

High performance glow discharge a-Si1−xGex:H of large x

Improvement of a-Si1−xGex:H single-junction thin-film solar cell performance by bandgap profiling techniques

The effects of native and light induced defects on optoelectronic properties of hydrogenated amorphous silicon–germanium (a-SiGe:H) alloy thin films

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