To improve the external quantum efficiency and maintain the high speed of metal-semiconductor-metal (MSM) photodetectors, a thin film inverted MSM (I-MSM), which is separated from the growth substrate, has fingers on the bottom of the device, and is bonded to a silicon host substrate, is reported for the first time. This device optimizes the tradeoff between speed and responsivity, demonstrating the improvement in responsivity that can be achieved using an I-MSM. The photodetector time domain response at λ = 1.3 μm is 50 ps FWHM, with a 34 ps rise time and a 85 ps fall time.