An AlInAs/GaInAs high electron mobility transistor (HEMT) has been monolithically integrated with an InP/GaInAs pin photodiode for the first time. Transconductance of the integrated HEMT is 270 mS/mm at 1 μm gate length. The high transconductance has resulted in improved receiver sensitivity, −23.7 dBm at 2 Gbit/s.