We demonstrate optical response from a side-injection light-controlled bistable laser diode buried with semi-insulating InP using hydride vapor phase epitaxy. The buried surface around both the ⟨110⟩ and⟨−110⟩oriented mesas is flat. The bistable operation is obtained by applying control voltage to the saturable absorption region. After optimization of the device parameters, we obtained error-free operation at a bit rate as high as 2.5 Gbit/s. ©1997 American Institute of Physics.