New silicon epitaxial avalanche diode for single-photon timing at room temperature

Avalanche Photodiodes in Submicron CMOS Technologies for High-Sensitivity Imaging

“…This in turn implies a breakdown voltage variation across the active region, which strongly affects the homogeneity of the photon detection efficiency (Ghioni et al, 2007). Thirdly, the increase of the quasi-neutral field region at the detector edge promotes late diffusion of minority carriers into the central high-field region, resulting in a long diffusion tail in the timing resolution characteristic, first reported in (Ghioni et al, 1988), and also evident in the 130nm implementation of (Niclass et al, 2007). Fourthly, this structure has a minimum diameter limitation due to merging of the guard ring depletion region as the active region is reduced, illustrated in (Faramarzpour et al, 2008).…”

“…The timing resolution, or 'jitter' of the detector is the full-width, half-maximum (FWHM) measure of this temporal variation. Among the timing resolution components are the variation caused by the generated carrier transit time from depletion layer to multiplication region, which is dependent on the depth of absorption of the incident photon (as a guideline, the transit time at carrier saturation velocity is 10ps per micron), and, more important, the statistical build up of the avalanche current itself (Ghioni et al, 1988). This is impacted by the electric field strength, and so jitter may be minimised by employing high overall bias conditions.…”

“…b. The enhancement mode structure, first introduced in the reach-through device of (Petrillo et al, 1984), was employed in a hybrid diffused guard ring/enhancement structure (Ghioni et al, 1988), and finally used without the diffused guard ring structure (Lacaita et al, 1989), relying on a single central active region enhancement implant (with doping polarities reversed, and embedded in a dual layer P-epitaxial substrate), which is referred to as a 'virtual' guard ring structure. The benefits of this structure are significant.…”

“…e. The work of the research group at Politecnico di Milano has prioritised timing resolution as the key performance metric since early publications utilising the diffused guard ring structure (Cova et al, 1981). This focus was maintained in the progression to devices implemented in a custom epitaxial layer (Ghioni et al, 1988). It was observed that previously published devices exhibited a long diffusion tail in the timing response.…”

Single photon avalanche detectors: prospects of new quenching and gain mechanisms

“…To this end, thin Si detectors came into favour due to the lower operating bias and reduced carrier-diffusion length. The double-epitaxial device structure developed by Cova [43] is similar to the simple planar diode but with an n-type starting substrate and two thin expitaxial p-type layers. The active area is defined by the centre top highly doped p region, which is around 10-50 µm, and the breakdown voltage is around 15-50 V. The higher p-doping region was established in the cen- The design is similar to the planar epitaxial design, except the low resistance p++ layer is broken underneath the active region to allow for wider epistrate/substrate depletion region.…”