Since the first bipolar transistor was investigated in 1947, enormous efforts have been devoted to semiconductor devices. The strong world wide competition in fabricating metal-oxide-semiconductor field-effect of develop transistor (MOSFET) memories has accelerated the pace ments in semiconductor technology. Bipolar transistors play a major role due to their high-speed performance. Delay times of about 20 ps per gate have already been achieved. Because of this rapid technologi cal progress, it is difficult to predict the future with any certainty. In 1987 a special session on ultrafast...