Edge-illuminated refracting-facet photodiode with large bandwidth and high output voltage

A high-speed and high-output-voltage edge-illuminated refracting-facet photodiode (RFPD) has been developed by employing a thin absorption layer. In the RFPD, the incident light parallel to the up-side surface is refracted at an inwardly angled facet and penetrates at a small angle in the absorption layer. The absorption length is thus effectively longer, resulting in high responsivity even at a thin absorption layer. In addition, since this RFPD uses a p-metal as a reflector, the absorption length is doubled. The light penetration at a small angle in the absorption layer also reduces the carrier density, and thinning the absorption layer effectively suppresses the influence of field modulation due to space charges. The fabricated RFPD has a responsivity as high as 0.69 A/W for 1.55 μm light even with an absorption layer as thin as 0.43 μm, a maximum 3 dB bandwidth of 66 GHz, and a high output peak voltage of over 2.5 V.