Top-illuminated metamorphic In0.53Ga0.47As p-i-n photodetectors are grown on the ultrathin low-temperature InP buffered GaAs substrates. Photodetectors with the 300-nm-thick In0.53Ga0.47As absorption layer show a typical responsivity of 0.12 A/W to 1.55-micron optical radiation, corresponding to an external quantum efficiency of 9.6%. Photodetectors with the active area of 50*50 (microns) exhibit the -3 dB bandwidth up to 6 GHz. These results are very encouraging for the application of this metamorphic technology to opto-electronic integrated circuit (OEIC) devices.