Integrated multiquantum well heterojunction bipolar transistors for optical switching and thresholding applications

The integrating-thresholding properties of an integrated bipolar device realized by molecular beam epitaxy are demonstrated, and switching characteristics for 10 mu W input to the controller are measured. The device is based on the quantum confined Stark effect in multiquantum wells. The controller, which is a bipolar transistor with a MQW collector region, provides an amplified photocurrent and feedback voltage to switch the modulator. Cascadability, optoelectronic amplification, and multistage operation are demonstrated in terms of a fan-out of eight devices. The integrating-thresholding properties also lend themselves to the implementation of neurons and to the realization of decision-making processes. The controller-modulator device can form a versatile basic module for optical computation architectures.<>