Metal-semiconductor-metal (MSM) polysilicon photodetectors which are compatible with all standard complementary
metal-oxide-semiconductor (CMOS) processes and which were made in a commercial 0.35 ìm process have
demonstrated DC responsivities up to 1.3 A/W at 690 nm. An effective absorption coefficient of 0.63 dB/ìm was found
from a comparison of responsivities of 5- and 10-μm long detectors. For a constant bias voltage, responsivity varies as
the inverse square of the contact spacing, with responsivity continuing to increase for the smallest available contact
spacing devices. Responsivities corresponding to quantum efficiencies over 200% were observed, implying a gain
mechanism. For AC performance, electrical pulse full-width at half-maximum (FWHM) as low as 0.81 ns and 10% -
90% rise times as low as 0.39 ns have been measured in response to ~0.65 ns FWHM optical input pulses. The ability
to modulate the source laser diode limits the measured pulse performance of the detectors. Observed DC and pulse
results are well explained by an analytic expression which incorporates the effects of bulk and contact recombination.
Possible means of improving the detector speed are proposed.2
CMOS technology scaling especially in the sub-100 nm
regime has made signaling in long global a challenge,
resulting in a need for an improved interconnect technology.
Optical signalling is a promising alternative to
existing global interconnects and alleviates interconnect
bottle-neck. This paper presents a design of a CMOS
trans-impedance amplifier (TIA) that is intended for a
truly CMOS compatible on-chip optical clock distribution
system. This TIA employs replica biasing technique
to achieve stability while maximizing its bandwidth and
gain. The design was implemented in a 0.35μm CMOS
process and is currently under probe testing. The simulation
results show that the design achieved a bandwidth of
1GHz and gain of 128dB-Ω. Extensive Monte-Carlo simulations
indicate the superior characteristics of stability
under a variety of process and environmental variations.
A novel, truly CMOS compatible, waveguide coupled, high-speed photodiode for on-chip optical clock distribution is designed using analytical calculations, electro-optical simulations, and experimental analysis. Experiment and simulation results from test devices are presented and analyzed.