Using double heterojunction structure with linearly graded In x Al 1– x As as buffer layer and In 0.9 Al 0.1 As as cap layer, wavelength extended In 0.9 Ga 0.1 As detectors with cutoff wavelength of 2.88μm at room temperature have been grown by using gas source molecular beam epitaxy, their characteristics have been investigated in detail and compared with the detectors cutoff at 2.4μm with similar structure as well as commercial InAs detectors. Typical resistance area product R 0 A of the detectors reaches 3.2Ωcm 2 at 290K. Measured peak detectivity reaches 6.6E9cmHz 1/2 /W at room temperature.