Silicon, amorphous, electronic

Amorphous Silicon. Amorphous alloys made of thin films of hydrogenated siUcon (a-Si H) are an alternative to crystalline siUcon devices. Amorphous siUcon ahoy devices have demonstrated smah-area laboratory device efficiencies above 13%, but a-Si H materials exhibit an inherent dynamic effect cahed the Staebler-Wronski effect in which electron—hole recombination, via photogeneration or junction currents, creates electricahy active defects that reduce the light-to-electricity efficiency of a-Si H devices. Quasi-steady-state efficiencies are typicahy reached outdoors after a few weeks of exposure as photoinduced defect generation is balanced by thermally activated defect annihilation. Commercial single-junction devices have initial efficiencies of ca 7.5%, photoinduced losses of ca 20 rel %, and stabilized efficiencies of ca 6%. These stabilized efficiencies are approximately half those of commercial crystalline shicon PV modules. In the future, initial module efficiencies up to 12.5% and photoinduced losses of ca 10 rel % are projected, suggesting stabilized module aperture-area efficiencies above 11%. 

Nathan, A. et al.. Amorphous silicon backplane electronics for OLED displays, IEEE J. Selected Topics in Quantum Electronics, 10, 58, 2004. 

Disordered covalent materials such as amorphous silicon, hydrogenated amorphous silicon, amorphous carbon, and diamondlike carbon are of current interest because they are important in technological applications. The TBMD scheme will be very useful in the study of the microscopic structural, dynamical, and electronic properties of these complex systems. 

The status of the dye-sensitized device as the only verified alternative to solid-state junction devices has already been discussed. It must be recognized that the solid-state devices, particularly the silicon p-n junction cells benefit from forty years of industrial and development experience, the technology transfer from the silicon-based electronics industry, and even the widespread availability of high-quality silicon at low cost resulting from the expansion of that industry. The procedures for high-yield fabrication of silicon devices, both crystalline and amorphous, are well understood, with costing well established on the basis of decades of solid industrial experience. For dye-sensitized... 

Biegelsen, Electron Spin Resonance Studies of Amorphous Silicon, Proc. Electron Resonance Symp. 3 85 (1981). dler and and F.R. Shapiro, Effective Correlation Energy of the Dangling Bond in Amorphous Silicon, Physica 117B and 118B 932 (1983). ... 

Therefore it is reasonable to prepare already the data acquisition for a three dimensional evaluation in cone-beam-technique by means of two-dimensional detectors. The system is already prepared to integrate a second detector- system for this purpose. An array of up to four flat panel detectors is foreseen. The detector- elements are based on amorphous silicon. Because of the high photon energy and the high dose rates special attention was necessary to protect the read-out electronics. Details of the detector arrangement and the software for reconstruction, visualisation and comparison between the CT results and CAD data are part of a separate paper during this conference [2]. 

Fig. 4. Some electronic device applications using amorphous silicon (a) solar cell, (b) thin-fiLm transistor, (c) image sensor, and (d) nuclear particle detector.

In disordered materials such as amorphous silicon, the mobility is so low that it would correspond to a mean free path lower than the distance between atomic sites, which is not physically pertinent. In a classical paper, Anderson [20 has shown that disorder in a solid may result in a localization of the states, in which case the one-electron wave function takes an exponential form... 

Probe measurements in silane discharges have been reported [296,297]. Apparently, no difficulties were experienced, as the deposited amorphous silicon layer on the tip was sufficiently photoconductive. For typical silane discharge conditions values for are found to be between 2 and 2.5 eV. Electron densities are around 1 x 10 cm - [296]. Probe measurement in the ASTER system failed due to strong distortions of the probe current, even after following cleaning procedures. 

In the early 1970s, Spear and coworkers (Spear, 1974 Le Comber et al., 1974), although unaware of the presence of hydrogen, demonstrated a substantial reduction in the density of gap states (with a corresponding improvement in the electronic transport properties) in amorphous silicon films that were deposited from the decomposition of silane (SiH4) in an rf glow discharge. 

As described earlier, the covalently bonded hydrogen, by passivating dangling bond defects and removing strained weak Si—Si bonds from the network, dramatically improves the semiconducting quality of amorphous silicon. Hence without the presence of hydrogen, effective amorphous semiconductor devices such as solar cells or thin film transistors would not be possible. Unfortunately, low defect density, high electronic quality... 

P.G. LeComber, A.E. Owen, W.E. Spear, J. Hajto, and W.K. Choi, Electronic Switching in Amorphous Silicon Junction Devices... 

Hong, C. Wagner, S. 2000. Inkjet printed copper source/drain metallization for amorphous silicon thin-film transistors. IEEE Electron Dev. Lett. 21 384-386. 

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