Facilely Achieved Self‐Biased Black Silicon Heterojunction Photodiode with Broadband Quantum Efficiency Approaching 100%

Abstract

Photodiodes are fundamental components in modern optoelectronics. Heterojunction photodiodes, simply configured by two different contact materials, have been a hot research topic for many years. Currently reported self‐biased heterojunction photodiodes routinely have external quantum efficiency (EQE) significantly below 100% due to optical and electrical losses. Herein, an approach that virtually overcomes this 100% EQE challenge via low‐aspect‐ratio nanostructures and drift‐dominated photocarrier transport in a heterojunction photodiode is proposed. Broadband near‐ideal EQE is achieved in nanocrystal indium tin oxide/black silicon (nc‐ITO/b‐Si) Schottky photodiodes. The b‐Si comprises nanostalagmites which balance the antireflection effect and surface morphology. The built‐in electric field is explored to match the optical generation profile, realizing enhanced photocarrier transport over a broadband of photogeneration. The devices exhibit unprecedented EQE among the reported leading‐edge heterojunction photodiodes: average EQE surpasses ≈98% for wavelengths of 570–925 nm, while overall EQE is greater than ≈95% from 500 to 960 nm. Further, only elementary fabrication techniques are explored to achieve these excellent device properties. A heart rate sensor driven by nanowatt faint light is demonstrated, indicating the enormous potential of this near‐ideal b‐Si photodiode for low power consuming applications.

Haynes-Shockley experiment analogs in surface and optoelectronics: Tunable surface electric field extracting nearly all photocarriers

“…4E ) is compared with the EQE for an annealed device at 0 V in fig. S14 ( 58 ). For the unannealed devices in this work, there is a limited chemical passivation effect at the surface, while the annealed device shows excellent surface chemical passivation ( 58 ).…”

“…S14 ( 58 ). For the unannealed devices in this work, there is a limited chemical passivation effect at the surface, while the annealed device shows excellent surface chemical passivation ( 58 ). In our previous work, it is demonstrated that a wide depletion region and a well chemically passivated surface enable a nearly complete collection of broadband photocarriers at 0 V bias ( 58 ).…”

Excellent Responsivity and Low Dark Current Obtained With Metal-Assisted Chemical Etched Si Photodiode

“…While MACE has previously been applied to Schottky photodiodes [26], [27], it is well known that they always suffer from high dark current and, consequently, have limited sensitivity. For instance, Zhang et al [26] have recently reported a high-responsivity MACE Si Schottky photodiode; however, the achieved dark current density is as high as 130 nA cm −2 at −1-V bias, which cannot compete with commercial Si photodiodes (typically <10 nA cm −2 ). Unlike Schottky diodes, p-n diodes are known for their low dark currents.…”

Design and Optimization of High-Responsivity High-Speed Ge/Si Avalanche Photodiode in the C+L Band

“…A diverse range of measures, including on-silicon lead-free halide perovskite single-crystalline thin film (SCTF), nanostalagmite structures, Ge nanowires, grating structures, graphene interlayer, reflector mirror, and tensile strain, have been investigated to enable high-performance photodetectors [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. Of them, tensile strain is considered an effective measure to enhance the optical properties of Ge [ 15 ].…”