Properties of GexSi1−xstrained‐layerp‐i‐ndetectors, in which the strained‐layer superlattice itself was used as an absorption region, have been studied for the first time. These devices were grown on (100)Si by molecular beam epitaxy. Using waveguide geometry we have obtained internal quantum efficiencies on the order of 40% at 1.3 &mgr;m in superlattices with the Ge fractionx=0.6. The superlattice detectors show the frequency response bandwidth of over 1 GHz and uniformly excellent electrical characteristics for values ofxas large as 0.8.