Photon-trapping-enhanced avalanche photodiodes for mid-infrared applications

Abstract

The fast development of mid-wave infrared photonics has increased the demand for high-performance photodetectors that operate in this spectral range. However, the signal-to-noise ratio, regarded as a primary figure of merit for mid-wave infrared detection, is strongly limited by the high dark current in narrow-bandgap materials. Therefore, conventional mid-wave infrared photodetectors such as HgCdTe require cryogenic temperatures to avoid excessively high dark current. To address this challenge, we report an avalanche photodiode design using photon-trapping structures to enhance the quantum efficiency and minimize the absorber thickness to suppress the dark current. The device exhibits high quantum efficiency and dark current density that is nearly three orders of magnitude lower than that of the state-of-the-art HgCdTe avalanche photodiodes and nearly two orders lower than that of previously reported AlInAsSb avalanche photodiodes that operate at 2 µm. Additionally, the bandwidth of these avalanche photodiodes reaches ~7 GHz, and the gain–bandwidth product is over 200 GHz; both are more than four times those of previously reported 2 µm avalanche photodiodes.

Enhancing Extended SWIR Al0.3InAsSb PIN Photodetectors with All-Dielectric Amorphous Germanium Photon-Capturing Gratings

“…Compared to directly etching the photodetector into microstructures to enhance light absorption, , placing an a-Ge grating on top does not introduce a significant additional surface leakage current that would increase the dark current (Figure S2). Furthermore, when compared to the utilization of metal nanostructures, − an all-dielectric a-Ge grating avoids substantial optical loss. It is cost-effective and much easier to fabricate through plasmonic dry etching.…”

“…7−9 Previously, we have reported light absorption enhancement in SACM digital alloy Al 0.3 InAsSb APDs operating at 2 μm. 10,11 This enhancement was achieved by implementing a photon-trapping structure created by using gold (Au). Other papers also report using Au nanostructure to enhance the field of photodetector through plasmonic effect.…”

“…Digital alloy Al x In 1– x As y Sb 1– y has been demonstrated as a tunable material system that can be used to create eSWIR separate absorption, charge and multiplication (SACM) avalanche photodiodes (APDs). − Previously, we have reported light absorption enhancement in SACM digital alloy Al 0.3 InAsSb APDs operating at 2 μm. , This enhancement was achieved by implementing a photon-trapping structure created by using gold (Au). Other papers also report using Au nanostructure to enhance the field of photodetector through plasmonic effect. − However, gold, being a noble metal, presents challenges due to its cost and the complexity of fabricating dense nanostructures with high aspect ratios by using conventional lift-off techniques.…”

Achieving higher photoabsorption than group III-V semiconductors in ultrafast thin silicon photodetectors with integrated photon-trapping surface structures

“…Later, several similar techniques with such microhole structures were utilized in realizing efficient and ultrafast photodetectors, avalanche photodetectors, and high-performance single-photon avalanche photodetectors 46 – 49 It should be noted that photodetectors usually operate under reverse bias conditions, while solar cells are designed to operate at maximum power points and are used under zero bias. To circumvent the arduous device fabrication processes, researchers measured the quantum efficiencies using 1−T−R, where T and R are transmission and reflection of the illuminated light 20 , 21 , 24 .…”

Nonlocal, Flat-Band Meta-Optics for Monolithic, High-Efficiency, Compact Photodetectors

“…Resonant cavity-enhanced absorption occurs as the optical cavity traps light for a longer time period, which increases the absorption efficiency. Various dielectric and plasmonic resonators have been used to enhance the photon-to-electron conversion efficiency of PDs in silicon ,, and other materials. − However, these results all focus on normal incident light and thus are incompatible with lens-based concentrators (Figure b), as focused light contains a wide range of incidence angles. Therefore, an angle-independent resonant cavity can both enhance the light absorption and be compatible with a light concentrator to enhance the photoresponsivity (Figure c).…”