Ballistic nanodevices for terahertz data processing: Monte Carlo simulations

Abstract

By using a semi-classical two-dimensional Monte Carlo simulation, simple devices (T-branch junctions (TBJs) and rectifying diodes) based on AlInAs/InGaAs ballistic channels are analysed. Initially, the model is validated by means of Hall-effect measurements of mobility and electron concentration in long (diffusive) channels. Then, quasi-ballistic transport at room temperature is confirmed in a 100 nm channel. Our simulations qualitatively reproduce the experimental results of electric potential measured in a TBJ appearing as a result of electron ballistic transport, and in close relation with the presence of space charge inside the structure. As examples of devices exploiting the ballistic transport of electrons, preliminary simulations of a multiplexor/demultiplexor and a rectifying diode are presented, demonstrating their capability for terahertz operation.

THz operation of self-switching nano-diodes and nano-transistors

“…Within the FV simulations the layer structure is taken into account, but the device in the z dimension is considered to be homogeneous. This kind of simulations can be useful for the modeling of simple structures, like homogeneous channels or classical transistors 7,8,12,14 . On the other hand, to account for the top geometry of more complicated devices (such as our SSDs and SSTs) TV simulations will be carried out.…”

“…It is important to remark that the operating principle of SSDs, unlike other semiconductor nanodevices (TBJs, YBJs, ballistic rectifiers), [7][8][9] is not based on ballistic transport or high mobility, and therefore SSDs could also be fabricated on…”

“…Some theoretical descriptions of the operation of ballistic devices have been proposed [2][3][4] , always starting from a coherent transport description based on the Landauer-Buttiker formalism 5,6 . In this work we will make use of a semiclassical 2D Monte Carlo (MC) simulation [successfully employed in previous works for the modelling of different types of InGaAs-based nanodevices: T-and Y-branch junctions and ballistic rectifiers [7][8][9][10][11] ] to explain the physics of the operation of InAlAs/InGaAs based SSDs and SSTs. MC simulations provide an insight of the processes taking place inside the devices, thus allowing us to relate the macroscopic results of the experiments with the microscopic behavior of electrons.…”

Characterization of GaAs-Based Three-Branch Nanowire Junction Devices by Light-Induced Local Conductance Modulation Method

“…In the case of the n-type semiconductor, the channel depletion occurs in the positively biased branch, as shown in Fig. 2(b) [19][20][21][22][23][24][25][26] .…”

“…However, experimentally, it is also clearly observed at room temperature (RT) [14][15][16][17][18] where the carrier transport should be in the nonballistic transport regime. The mechanism in such a case has not been clarified yet, although several hypotheses have been introduced, including those regarding the effective mean free path extension 16) and the asymmetric channel depletion due to the surface potential [19][20][21][22][23][24][25][26] .…”