Acoustic phonon-assisted resonant tunneling via single impurities

Abstract

We perform the investigations of the resonant tunneling via impurities embedded in the AlAs barrier of a single GaAs/AlGaAs heterostructure. In the I(V) characteristics measured at 30 mK, the contribution of individual donors is resolved and the fingerprints of phonon assistance in the tunneling process are seen. The latter is confirmed by detailed analysis of the tunneling rates and the modeling of the resonant tunneling contribution to the current. Moreover, fluctuations of the local structure of the DOS ͑LDOS͒ and Fermi edge singularities are observed.

Fermi-edge singularities in transport through quantum dots

“…The change of occupation of the local levels during the tunneling process generates sudden changes of this scattering potential leading to characteristic singularities in the I-V curves at the corresponding voltage threshold. [4][5][6][7][8][9] A theoretical analysis of the low energy response, i.e., in the vicinity of these singularities, at zero temperature is possible using bosonization techniques. 10 In this approach the response functions can be expressed as correlation functions of boundary changing operators in an equivalent 1 + 1 dimensional conformal field theory.…”

Current Fluctuations in Single Barrier Vertical GaAs/AlAs/GaAs Tunneling Devices

“…2a) has been measured in the range from 0 V to -1 V at a temperature T = 4.2 K. Minus sign in the biasing voltage means the current flowing from the substrate to metallic contact on the top of the mesa structure. The most important feature of this characteristics is the bump in the region from -0.45 to -0.75 V, where the tunneling current is mediated by silicon impurities in the center of the barrier [4,5]. More fea- tures can be seen in differential conductance characteristics (Fig.…”

“…2c has values between 0.7 for higher biases and 1 for lower. Astonishingly, the Fano factor close to F = 0.85 is observed in the range from -0.4 V to -0.55 V, where in I(V ) characteristics the resonant tunneling through the impurity states is observed [4,5]. The Fano factor close to F = 0.75, expected for tunneling through strongly localized states randomly distributed in the center of the barrier [7,8], is observed for biasing voltages higher than 0.8 V. However, because of the large dispersion of the Fano factors the conclusions from this discussion should be limited.…”

Transport in GaAs/AlAs/GaAs [111] Tunnel Junctions

“…If, in addition, the barrier is doped, also the donor states can participate in the resonant tunneling. This is especially interesting, as a discrete level of a single impurity can be used as a local probe of the tunneling electron gas [1,2]. However, if the structure is grown along [001] direction, due to strain and anisotropy of X minimum, the donor state is split into two components separated by ≈ 20 meV [3].…”