Ballistic Electron Contributions in Vertically Integrated Resonant Tunneling Diodes

Abstract

Understanding coherent transport of electrons below (see e.g. Lakhani et al., 1988; England et al., 1989; Vendgurlekar et al., 1990) or above the barriers (Beltram et al., 1989; Gaylord and Brennan, 1988) is important in developing complex quantum well devices. Studies of current-voltage (I–V) curves as a function of the doped spacer layer width (W _sp) separating two vertically-integrated resonant tunneling diodes (VIRTD) structures have shown quantum interference effects depend on the spacer width (Wolak et al., 1989). Our work examines ballistic transport across the doped spacer layer and resonant tunneling through quantum levis in the collector RTD. Using a transverse magnetic field B we “tuned” the longitudinal momentum of the ballistic portion of the current. The magnetic field effects on the ballistic electron component became more evident as the doped spacer layer width decreased (0 < W _sp < 100 nm). For W _sp = 50 nm, there is a threshold magnetic field at which the ballistic electrons become resonant with a quasi-bound level in the collector well, leading to dramatic changes in the I–V characteristics. In the strong coupling case (W _sp = 0), there is a B-induced enhancement of resonant tunneling across the whole structure and a resonance from Γ-X intervalley tunneling.

Work supported inpart by the National Science Foundation through DMR grant 87–196344 and the NSF-CNRS collaborative grant INT-88–15314.