Improving performance of resonant tunneling devices in asymmetric structures

Based on the global coherent tunneling model, we present a self-consistent calculation and show that structural asymmetry of double barrier resonant t unneling structures (DBRTSs) significantly modifies the current-voltage cha racteristics compared to the symmetric structures. Within the framework of the dielectric continuum model, we further investigate the phonon-assisted tunneling (PAT) current in symmetric and asymmetric DBRTSs. Both the interf ace modes and the confined bulk-like longitudinal-optical phonons are consi dered. The results indicate that the four higher-frequency interface phonon modes (especially the one which has the largest electron-phonon interactio n at either interface of the emitter barrier) dominate the PAT processes. W e show that a suitably designed asymmetric structure can produce much large r peak current and absolute value of the negative differential conductivity than its commonly used symmetric counterpart. (C) 2001 Elsevier Science B. V. All rights reserved.