Solid source molecular beam epitaxy was used to deposit in a continuous process an integrated metamorphic high electron mobility transistor (HEMT) and PIN photodiode structure. A metamorphic buffer layer was first grown on a GaAs substrate to expand the lattice constant to that of In0.53Ga0.47As used in the device layers. The HEMT layers were subsequently grown followed by the PIN diode structure. Cross-sectional and plan-view transmission electron micrographs showed planar layer interfaces and a dislocation density in the device layers of 1 x 10(6) cm(-2). The device characteristics of the HEMT transistors were not adversely affected by growth of the PIN structure on top. Also the bandwidth and responsivity of the metamorphic PIN photodiode were comparable to an InP PIN photodiode with similar dark currents. The integrated HEMT/PIN diode circuit had a 3 dB bandwidth 20% greater than a hybrid combination of devices due to a decrease in parasitic losses from device interconnects. The frequency performances of circuits fabricated from the same wafer. exhibited a high degree of uniformity. (C) 2004 American Vacuum Society.