CHARGE INJECTION TRANSISTORS AND LOGIC-CIRCUITS

The charge injection transistor or CHINT is a semiconductor device based on realspace transfer of hot electrons between two conducting layers, separated by a potential barrier. Recently, significant progress has been achieved at Bell Laboratories in the implementation of CHINT devices. Using InGaAs InAlAs heterostructure materials and novel epitaxial contacts, nearly ideal characteristics were obtained, e.g. an NDR with a peak-to-valley ratio approaching 104 at room temperature and a transconductance gm > 20 S/mm. The nature of hot-electron injection in CHINT allows the implementation of novel circuit elements. In particular, we have proposed and demonstrated a multiterminal single-device structure that works as a functional element with three symmetric logic inputs X1, X2, X3 and one output equal to (X1∩X2∩X3) ∪ (X1∩X2∩X3). This device, called the NORAND, can perform both as a NOR (X1, X2) and as an AND (X1, X2) element, reprogrammable electrically by changing the X3 input. The NORAND element permits the implementation of circuits in which the function of a particular logic element is not fixed by the layout but is reprogrammable in the course of the circuit operation. © 1990.