We present on high efficiency metal-insulator-semiconductor (MIS) photodetectors based on amorphous germanium quantum dots (QDs) embedded in a SiO 2 matrix. High internal quantum efficiencies (IQE) were achieved across a broad wavelength range, with peak value reaching 700% at -10 V applied bias due to high internal photoconductive gain. The transient photoresponse behavior is also studied and it was found that the response time of the photodetector depends on the thickness of the QD layer. We also discuss the conduction mechanism which leads to the high photoconductive gain.