We report on a novel implementation of long-wavelength vertically-coupled waveguide-integrated metal-semiconductor-metal (MSM) InGaAs photodetectors which results in a significantly improved guide-to-absorber coupling efficiency. By employing an In/sub 0.53/Al/sub 0.31/Ga/sub 0.16/As buried strip waveguide embedded in InP, a coupling length of only 20 /spl mu/m is sufficient to obtain an internal quantum efficiency greater than 95%. Moreover, the photoresponse is found to be virtually independent of the polarization state of light coupled into the input waveguide. The device parameters agree with the results of eigenmode calculations.