Dark current reduction in fused InGaAs/Si avalanche photodiode

Mesa type fused InGaAs/Si separated absorption and multiplication APDs with a diameter of 130 /spl mu/m have been fabricated on n-type Si substrate. Substantial dark current reduction has been achieved compared with the published data for fused InGaAs/Si APDs. Dark current densities as low as 0.23 mA/cm/sup 2/ at -5 V and 3 mA/cm/sup 2/ at a gain of 10 are reported. Our improved dark current even though is still 2 orders larger than the conventional mesa-structure InGaAs/InP APD lower excess noise level is expected due to the larger difference between the electron and hole ionization coefficients of Si.