Hydrogen content of plasma deposited a-Si:H

Abstract

Amorphous hydrogenated Si is deposited using a remote Ar/H plasma. The plasma is generated in a d.c. thermal arc and expands into a low pressure chamber (20 Pa). Pure silane is injected into the plasma jet immediately after the arc source in a typical flow mixt. of Ar:H2:SiH4 = 55:10:6 scc/s. At the low Te in the jet (0.3 eV), silane radicals are produced mainly by H abstraction. In-situ ellipsometry yields refractive indexes of 3.6-4.2 at 632.8 nm and growth rates of 10-20 nm/s. FTIR anal. yields a H content of 9-25 at.% and refractive indexes of 2.7-3.3 in the IR. The SiH d. decreases with increasing H content, whereas the SiH2 d. increases, indicating a deterioration of the microstructure. The optical bandgap remains const. at .apprx.1.72 eV. The photocond. is of the order 10-6 (Wcm)-1 and the photoresponse 106. [on SciFinder (R)