Localised feedback in silicon-based avalanche photodiodes

Avalanche photodiode structures with wide-bandgap (WBG) barrier on epitaxial silicon layers of 4–20 μm thickness were studied and fabricated for short-wavelength photons (∼0.4 μm) detector. To optimise avalanche multiplication and current transport processes, a physical model has been developed taking into account charge transport localisation mechanisms in silicon and WBG layer. To reduce lateral spreading of current filaments, the nanostructuring of WBG layer has been proposed. The nanostructured WBG layer includes semiconductor nanoclusters between which electrons may tunnel to reach the field electrode. Thus, additional localisation of every separate avalanche region (filament) is provided. The current outflow mechanism through this structure is characterised by a delay caused by multiple tunnelling of electrons injected from semiconductor local region, where avalanche multiplication takes place, to WBG layer. For this mechanism the noise factor should be lower than for avalanche structures with resistive layer caused by the WBG layer nanoclusters configuration.