A high-saturation-current, back side-illuminated In0.53Ga0.47As photodiode with a partially depleted absorber has been fabricated and tested. The I dB small-signal compression current was 199 mA at 1 GHz for a 100 pm diameter photodiode. The I dB large-signal compression current was 24 mA at 48 GHz for an 8 pm-diameter photodiode. The responsivity was 0.6 A/W at 1.55 mum.