This paper reports a metal-semiconductor-metal（MSM）Schottky photodiode （MSM-PD）array as an optoelectronic self-mixer factured on the extension layer which is grown on GaAs by using low pressure metal organic chemical vapor deposition （LP-MOCVD）method.There are 32×32 pixels in the device.Measured at 3 V biasing voltage,the responsivity of the device is 8.25 A/W,the dark current is under 18 nA,the consistency of photocurrent is 59.1 μA/cm2 and the input saturated power of light is 1 μW.Measuring the response to pulses,the risetime is 212 ps and the Full Wave at Half Maximum（FWHM）is 372 ps,so the corresponding 3-dB bandwidth is 1.65 GHz.