BALLISTIC CURRENT-VOLTAGE CHARACTERISTICS OF SEMICONDUCTOR SUPERLATTICE ELECTRON-WAVE QUANTUM-INTERFERENCE FILTER EMITTER NEGATIVE DIFFERENTIAL RESISTANCE DEVICES

The transmission and current-voltage characteristics of Ga1-xAlxAs superlattice electron-wave quantum-interference filter/emitter negative differential resistance devices are analyzed with and without the self-consistency requirement. The analysis neglects the scattering effects within the superlattice since it is assumed that it is very thin (less than the electron coherence length). Thus, the calculated characteristics correspond to the ballistic component of the current. For the non-self-consistent calculation the single-band effective-mass time-independent Schroedinger equation is solved. For the self-consistent calculation, the Schroedinger and Poisson equations are solved iteratively until a self-consistent electron potential energy and electron density are obtained. It is shown that suitably designed electron-wave quantum-interference filter/emitters can exhibit strong negative differential resistance in the current-voltage characteristics, similar to those of resonant tunneling diodes. For low-to-moderate (2-30 meV) Fermi energies in the conduction band of Ga1-xAlxAs (Si doping concentration less or equal to 2 x 10(18) cm-3) and temperatures near 30 K (in the ballistic transport regime), it is shown that space-charge effects are relatively small and result in a slight shift of the current-voltage and transmission characteristics toward higher bias voltages. In a fashion similar to that occurring in resonant tunneling diodes, the self-consistent field in electron-wave filter/emitter negative differential resistance devices partially screens the positive applied bias. Designs of Ga1-xAlxAs resonant devices with current peak-to-valley ratios of approximately 50 as well as nonresonant (not exhibiting negative differential resistance) devices are analyzed. The corresponding electron charge density distributions are also presented. Superlattice electron-wave filter/emitter negative differential resistance devices can be used as high-speed switches, oscillators, and as monoenergetic emitters in electroluminescent devices and photodetectors.