A novel ultrafast functional device: resonant tunneling high electron mobility transistor

Resonant-tunneling transistors (RTTs) are emerging as promising functional devices for achieving high functionality and reduced circuit complexity in integrated circuits. Many RTTs have been proposed and demonstrated. Most of these concepts are based on integrating a resonant tunneling diode (RTD) structure into one or more terminals of conventional transistors. In this paper, we demonstrate an InP-based resonant-tunneling high electron mobility transistor (RTHEMT) which integrates a pseudomorphic In/sub 0.53/Ga/sub 0.47/As-AlAs-InAs RTD into the source of a non-alloyed ohmic contact InAlAs-InGaAs HEMT. Employing the non-alloyed ohmic contact cap layer structure in the HEMT significantly reduces the interconnection resistance between the RTDs and the HEMTs, and therefore, high P/V ratios and small hysteresis are maintained in the output characteristics. The device exhibits both pronounced negative differential resistance (NDR) and negative transconductance at room temperature. Most importantly, a near-flat valley current is obtained in the output I-V characteristics at certain gate voltages. This unique feature of flat valley current leads to the observation of pronounced negative transconductance throughout a wide bias range. As a result RTHEMTs can be used for many circuit applications.