bipolarjunction transistor - (BJT), A three terminal device in which emitter to collector current is controlled by base current. junction diode - diode. A semiconductor diode in which the rectifying characteristics occur at a junction between the n-type and p-type semiconductor materials. junction - Contact or connection between two or more wires or cables. The area where the p-type material and n-type material meet in a semiconductor. unijunction transistor - Three terminal device that acts as a diode with its own internal voltage divider biasing circuit.