We propose and demonstrate a new lateral structure InP/InGaAs double heterojunction phototransistor (DHPT) which utilizes the interchangeability of the emitter and collector in double heterostructure. The lateral structure DHPT has the potential to have better high-frequency performance and requires simpler epitaxial layers than a vertical structure device. At 2 V bias, optical gains of 163 and 124 were obtained in 50 x 50 pm 2 area device and 20 x 20 mu m(2) device, respectively. Frequency response measurement exhibits optical power gains of 32 dB at 100 MHz and 8 dB at 1 GHz in the 20 x 20 mu m(2) device. Frequency response is also calculated numerically for a case of smaller active area device. (c) 2007 Elsevier Ltd. All rights reserved.