Multiplication noise of AlxGa1−xAs avalanche photodiodes with high Al concentration and thin multiplication region

We report that homojunction ${\mathrm{Al}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{As}$ avalanche photodiodes (APDs) exhibit very low multiplication noise when the Al content is ⩾80%. It was also found that, due to nonlocal effects, the multiplication noise decreased as the ionization region thickness was reduced from 0.8 μm to $\text{⩽0.2\hspace{0.5em}μ}\mathrm{m}$ for Al ratios (from 0 to 0.9). The excess noise factor of the thin (140 nm) ${\mathrm{Al}}_{\mathrm{0.9}}{\mathrm{Ga}}_{\mathrm{0.1}}\mathrm{As}$ APDs is the lowest reported to date for III–V compounds and is comparable to that of Si avalanche photodiodes.