Single-impurity tunneling spectroscopy to probe the discrete states of a two-dimensional electron gas in a quantizing magnetic field

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.…”

Spectroscopy of a Single Si Donor by the Resonant Tunnelling Experiment

“…We took advantage of the magnetic field studies of the Landau quantization for the structure b, reported in [3]. Knowing cyclotron energyhω c and separation between the Landau levels in the bias voltage scale, a so-called leverage factor α = ∆U/∆E was found (12.3 mV/meV).…”

“…The inset of presents a magnification of the low bias region. The structure present at about 0.9 V, marked with b, reflects the tunnelling via a single state of one impurity and it was discussed in more detail in [3]. Here we want to emphasize that the complicated shape of each structure (e.g.…”

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].…”