Integration of a variety of optical and electronic components monolithically on asingle chip of substrate is the goal of integrated optics. During the past few years a lotof effort has been put into the development of individual optical devices such as low-threshold single-mode GaAs lasers, waveguides, modulators, etc. On the other hand, agreat amount of progress has also been made on the high-speed GaAs electronic devicessuch as FET’s, Gunn oscillators, etc. However, the integration of these tWo kinds of de-vices has not been achieved. Recently, we succeeded, for the first time, in fabricatingGaAs heterostructure lasers on semi-insulating substrates. Because of the nonconductivesubstrate, the electrical integration can be performed on epilayers, and hence becomes Integration of a variety of optical and electronic components monolithically on asingle chip of substrate is the goal of integrated optics. During the past few years a lot of effort has been put into the development of individual optical devices such as low-threshold single-mode GaAs lasers , waveguides, modulators, etc. On the other hand, agreat amount of progress has also been on the high-speed GaAs electronic devicessuch as FET’s, Gunn oscillators, etc. However, the integration of these tWo kinds of de-vices has not has achieved. Recently, we succeeded, for the first time, in fabricating GaAs heterostructure lasers on semi-insulating substrates. Because of the nonconductive sub- stubstrate, the electrical integration can be performed on epilayers, and later