Coherent approach to transport and noise in double-barrier resonant diodes

Abstract

We implement a quantum approach which includes long range Coulomb interaction and investigate current voltage characteristics and shot noise in double-barrier resonant diodes. The theory applies to the region of low applied voltages up to the region of the current peak and considers the wide temperature range from zero to room temperature. The shape of the current voltage characteristic is well reproduced and we confirm that even in the presence of Coulomb interaction the shot noise can be suppressed with a Fano factor well below the value of 0.5. This feature can be an indication of coherent tunneling since the standard sequential tunneling predicts in general a Fano factor equal to or greater than the value 0.5. This giant suppression is a consequence of Pauli principle as well as long range Coulomb interaction. The theory generalizes previous findings and is compared with experiments.

Giant suppression of shot noise as signature of coherent transport in double barrier resonant diodes

“…For the current flowing from the emitter to the collector we found [5]: with q the electron charge, m its effective mass andh the reduced Planck constant. In our model, we suppose that in the emitter there are no electron states with energy below −g L and that electron states with energy higher than this value are three dimensional.…”

“…Thus, the giant suppression of shot noise predicted by present theory extends the previous findings of Wei et al [8] and is confirmed by these experiments. A recent set of experiments [5] carried out at 300 K on a DBRD with barriers thinner than those of [7], thus more adequate to check coherent tunnelling at high temperature, is reported in figure 3 together with theoretical calculations. The structure consisted of two 2 nm AlAs layers separated by 6 nm InGaAs quantum well [9].…”

“…To calculate noise we implemented the wave packet approach [6] to account for the self-consistent potential. Accordingly, for the spectral density of current fluctuations we obtain: [5] …”

“…In our model, we suppose that in the emitter there are no electron states with energy below −g L and that electron states with energy higher than this value are three dimensional. Furthermore, the relation between u and the total applied voltage V is calculated self-consistently by using the condition of electroneutrality of the device [5]. To calculate noise we implemented the wave packet approach [6] to account for the self-consistent potential.…”

Current shot noise characteristics in resonant tunneling step-barrier structures

“…Reklaitis et al 34 reported a Monte Carlo study of shot noise suppression in singleand multiple-barrier nonresonant heterostructure GaAs/ Al x Ga 1−x As diodes at 77 K and provided a microscopic investigation of the mechanisms responsible for shot noise suppression when transport under nondegenerate conditions is controlled by tunneling across barriers. Through both the sequential and coherent tunneling models, Aleshkin et al [35][36][37] presented a systematic study of current shot noise in ultrashort single barrier semiconductor structures and double-barrier resonant diodes. While the shot noise has been widely investigated for single-and double-barrier structures, [17][18][19][38][39][40][41][42][43] to our knowledge, there is no report on the shot noise of step-barrier structures.…”