We report the direct measurement of the intrinsic photocurrent response of both top and back illuminated planar metal–semiconductor–metal structures. We directly observe the temporal dynamics of the hole transport dependence on applied bias and the initial spatial distribution using a near infrared tunable femtosecond light source and electrically biased structures. The increased hole transit time of back illuminated structures can be completely understood in terms of the hole velocity and the initial spatial distribution of the carriers. Additionally, we report the fastest directly measured 50 &mgr;m diameter InGaAs photodetector with a 26 ps full width at half maximum. ©1995 American Institute of Physics.