Since the advent of impact ionization and its application
in avalanche
photodiodes (APD), numerous application goals have contributed to
steady improvements over several decades. The characteristic high
operating voltages and the need for thick absorber layers (π-layers)
in the Si-APDs pose complicated design and operational challenges
in complementary metal oxide semiconductor integration of APDs. In
this work, we have designed a sub-10 V operable Si-APD and epitaxially
grown the stack on a semiconductor-on-insulator substrate with a submicron
thin π-layer, and we fabricated the devices with integrated
photon-trapping microholes (PTMH) to enhance photon absorption. The
fabricated APDs show a substantially low prebreakdown leakage current
density of ∼50 nA/mm2. The devices exhibit a consistent
∼8.0 V breakdown voltage with a multiplication gain of 296.2
under 850 nm illumination wavelength. We report a ∼5×
increase in the EQE at 850 nm by introducing the PTMH into the device.
The enhancement in the EQE is evenly distributed across the entire
wavelength range (640–1100 nm). The EQE of the devices without
PTMH (flat devices) undergo a notable oscillation caused by the resonance
at specific wavelengths and show a strong dependency on the angle
of incidence. This characteristic dependency is significantly circumvented
by introducing the PTMH into the APD. The devices exhibit a significantly
low off-state power consumption of 0.41 μW/mm2and
stand fairly well against the state-of-the-art literature. Such high
efficiency, low leakage, low breakdown voltage, and extremely low-power
Si-APD can be easily incorporated into the existing CMOS foundry line
and enable on-chip, high-speed, and low-photon count detection on
a large scale.