The lateral current injection heterostructure field-effect laser structure is operated both as a three-terminal laser and a field-effect transistor. The structure was grown by low-temperature molecular-beam epitaxy (580-degrees-C) and excellent performance characteristics were obtained for both devices. The laser is shown to have both source/emitter and source/collector modes of operation. Both modes exhibited a continuous wave operation and the source/emitter mode has a - 3 dB bandwidth of 4 GHz limited by heating caused by a high source resistance. The transistor had a peak transconductance of 95 mS/mm and a peak drain to source current density of 120 mA/mm for a 2-mu-m X 50-mu-m device.