| 摘要 |
A very high transmittance, back-illuminated, silicon-on-thin sapphire-on-fused silica wafer substrate design is presented for enabling high quantum efficiency and high resolution, silicon or silicon-germanium avalanche photodiode detector arrays with improved indirect optical crosstalk suppression. The wafer substrate incorporates a stacked antireflective bilayer between the sapphire and silicon, comprised of single crystal aluminum nitride (AlN) and non-stoichiometric, silicon rich, amorphous silicon nitride (a-SiNX<1.33), as well as a one quarter wavelength, magnesium fluoride (λ/4-MgF2) back-side antireflective layer which is bonded to a fused silica wafer. The fused silica provides mechanical support, allowing the sapphire to be thinned to optimal thickness below 50μm, for improved optical transmittance and in conjunction with monolithic sapphire microlenses, suppression of indirect optical crosstalk from multiple reflections of APD emitted light. After solid-state device fabrication, the silicon can be coated with photoresist and the fused silica dissolved in buffered hydrogen fluoride (HF) to recover the thin Si—(AlN/a-SiNX<1.33)-sapphire-(MgF2).
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