There has been considerable interest in InGaAs photodiodes which respond in the long-wavelength range (1.0-1.6 μm) because of low dark-current characteristics.1,2 Recently, Kim et al. reduced the dark current of the photodiode by using a wide-band gap InGaAsP layer to decrease the surface leakage current.3 Campbell et al.4 have shown that the dark current can be reduced to values as low as 50 pA by using a semi-insulating InP cap layer. We present a new InGaAs/InP PIN photodiode with a covered-mesa (CM) structure. Dark currents as low as 20 pA have been achieved with this structure.
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