Boron doping of amorphous hydrogenated silicon films prepared by r.f. sputtering
Amorphous hydrogenated silicon (a-Si:H) films 1 μm thick were prepared at 190 and 250 °C by r.f. sputtering in an Ar-H 2-B 2H 6 gas mixture whose composition Y g = [B 2H 6]/([Ar] + [H 2]) was varied between zero and 10 -2. Measurements of the optical gap E 0 and the dark conductivity σ d give eviden...
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Published in | Thin solid films Vol. 124; no. 1; pp. 49 - 53 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Elsevier B.V
01.02.1985
|
Online Access | Get full text |
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Summary: | Amorphous hydrogenated silicon (a-Si:H) films 1 μm thick were prepared at 190 and 250 °C by r.f. sputtering in an Ar-H
2-B
2H
6 gas mixture whose composition
Y
g = [B
2H
6]/([Ar] + [H
2]) was varied between zero and 10
-2. Measurements of the optical gap
E
0 and the dark conductivity σ
d give evidence for the existence of three regions as a function of
Y
g. Up to
Y
g = 10
-6, the conductivity activation energy
E
a increases towards the intrinsic value
E
0/2. For
Y
g between 10
-6 and 10
-3,
E
0 and
E
a decrease to 1.5 eV and 0.4 eV respectively, indicating that efficient p-type doping is achieved. At higher diborane concentrations a boron-rich a-Si:B:H compound is formed which is not conductive. The photoconductivity ratio σ
ph/σ
d reaches its maximum value (of 10
3) at
Y
g ≈ 10
-6 and drops to unity for
Y
g ⩾ 10
-4. The loss in σ
ph is related to an increase in the density of states near the Fermi level as revealed by the onset of an important hopping conductivity on the σ
d curves. |
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ISSN: | 0040-6090 1879-2731 |
DOI: | 10.1016/0040-6090(85)90027-6 |