DocumentCode :
1562077
Title :
Real time spectroscopic ellipsometry of thin film Si1-xGex:H: phase diagrams for optimization in photovoltaics applications
Author :
Podraza, N.J. ; Ferreira, G.M. ; Albert, M.L. ; Chen, Chi ; Wronski, C.R. ; Collins, R.W.
Author_Institution :
Dept. of Phys. & Astron., Toledo Univ., OH, USA
fYear :
2005
Firstpage :
1393
Lastpage :
1396
Abstract :
The growth of silicon-germanium alloys (Si1-xGex:H) by plasma-enhanced chemical vapor deposition (PECVD) on crystalline silicon substrates has been studied by real time spectroscopic ellipsometry (RTSE). The motivation is to develop deposition phase diagrams that can be used in the optimization of amorphous Si1-xGex:H (a-Si1-xGex:H) for multijunction photovoltaics. In initial studies, the phase diagram for bottom cell a-Si1-xGex:H (Eg ∼ 1.4 eV) is found to exhibit basic similarities to that for Si:H prepared under the same PECVD conditions. This similarity suggests directions for optimizing a-Si1-xGex:H by identifying conditions under which smooth, stable surfaces are obtained to the largest possible bulk layer thicknesses. For low temperature (200 °C), low power PECVD of a-Si1-xGex:H, high surface stability and smooth surfaces are obtained by cathodic deposition (self bias: ∼ -20 V), using a H2-dilution level just below that of the amorphous-to-(mixed-phase microcrystalline) transition [a→(a+μc)].
Keywords :
Ge-Si alloys; amorphous semiconductors; crystallisation; ellipsometry; hydrogen; phase diagrams; plasma CVD; semiconductor growth; semiconductor thin films; 200 degC; PECVD; Si; Si1-xGex:H; amorphous-to-mixed-phase microcrystalline transition; bottom cell; cathodic deposition; crystalline silicon substrates; dilution level; multijunction photovoltaics; phase diagrams; photovoltaics applications; plasma-enhanced chemical vapor deposition; real time spectroscopic ellipsometry; silicon-germanium alloys; smooth surfaces; surface stability; thin film; Chemical vapor deposition; Crystallization; Ellipsometry; Germanium alloys; Germanium silicon alloys; Plasma chemistry; Semiconductor thin films; Silicon alloys; Silicon germanium; Spectroscopy;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Photovoltaic Specialists Conference, 2005. Conference Record of the Thirty-first IEEE
ISSN :
0160-8371
Print_ISBN :
0-7803-8707-4
Type :
conf
DOI :
10.1109/PVSC.2005.1488400
Filename :
1488400
Link To Document :
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