Commercial photodiodes suffer from reflection losses and different recombination losses that reduce the collection efficiency of photogenerated charge carriers. Recently, we realized a near-ideal silicon photodiode, which steps closer to the physical performance limits of silicon photodiodes than any other silicon photodiode realized before. Our device exhibits an external quantum efficiency above 95% over the wavelength range of 235 – 980 nm, and provides a very high response at incident angles of up to 70 degrees. The high quantum efficiency is reached by 1) virtually eliminating front surface reflectance by forming a “black silicon” nanostructured surface having dimensions in the range of wavelength of optical light and 2) using an induced junction for signal collection, formed by negatively charged alumina, instead of a conventional doped p-n junction. Here, we describe the latest efforts in further development of the photodiode technology. In particular, we report improvements both in the short wavelength response via better control of the surface quality, and superior response to photons with energies close to the silicon bandgap.
Juha Heinonen, Mikko A. Juntunen, Hannu S. Laine, Ville Vähänissi, Päivikki Repo, Timo Dönsberg, and Hele Savin, "Black silicon n-type photodiodes with high response over wide spectral range," Proc. SPIE 10231, Optical Sensors 2017, 102310X (Presented at SPIE Optics + Optoelectronics: April 26, 2017; Published: 16 May 2017); https://doi.org/10.1117/12.2264998.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon