Low dark current InGaAs(P)/InP p-i-n photodiodes

Planar InGaAs(P)/InP p-i-n photodiodes have been successfully fabricated by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). High-quality and uniform epitaxial layers are obtained. It is noted that the InGaAs layer background concentration is as low as 4.5 × 10¹³ cm^-3. The dark current is significantly reduced by using a wider-band-gap material of quaternary In_xGa_1-xAs_yP_1-y as a cap layer to reduce the device surface leakage current. In addition, the device becomes highly photosensitive due to the reduction of the absorption of the radiation in the narrow-band-gap In_xGa_1-xAs_yP_1-y cap layer. The p-i-n photodiode with a wide-band-gap InP cap layer exhibits a dark current as low as 60 pA at -10 V bias, corresponding to a dark current density of 4.2 × 10^-7 A/cm².