The authors have fabricated long-wavelength abrupt-junction InGaAs/AlInAs metal-semiconductor-metal photodetectors that are potentially compatible with AlInAs/InGaAs H-MESFETs. The detectors have nanoampere dark currents and low capacitance. The responsivity at 10 MHz is 0.32 A/W, corresponding to at least 90% internal collection efficiency. The device performance limitations due to charge storage at the InGaAs/AlInAs interface are discussed, and it is shown that despite charge pile up, high data rates (>3 GHz) have been achieved at low bias voltages, provided the incident intensity is low. >