APLANAR metal–semiconductor–metal photodetector
(MSM-PD) usually performs better and is simpler to
fabricate than the conventional p-i-n photodiodes [1], so
the MSM-PD is a good candidate for a photodetector in
an OEIC (optoelectronic integrated-circuit) receiver. Such c-
Si MSM-PD’s operated at a wavelength of 830 nm, which
are compatible with Si IC technology, have been recently
investigated [2]–[6]. However, the conventional c-Si MSMPD
usually has a high dark current, low responsivity, and
long pulse tail. To improve the performance of the c-Si MSMPD,
several methods, such as ion-implanting the absorbing
layer [4], and reducing the spacing between the interdigitated
electrodes [2] have been suggested. Ion-implantation is an
expensive process, and electrodes with a smaller spacing
would retard more incident light and are more difficult
to fabricate. Since the amorphous semiconductor has a
larger optical absorption coefficient and dark resistance,
and a shorter carrier lifetime [7], then, a hydrogenated
intrinsic amorphous silicon (i-a-Si:H) barrier layer forming an