A self-consistent, one-dimensional solution of the Schrödinger and Poisson equations is obtained using the finite-difference method with a nonuniform mesh size. The use of the proper matrix transformation allows preservation of the symmetry of the discretized Schrödinger equation, even with the use of a nonuniform mesh size, therefore reducing the computation time. This method is very efficient in finding eigenstates extending over relatively large spatial areas without loss of accuracy. For confirmation of the accuracy of this method, a comparison is made with the exactly calculated eigenstates of GaAs/AlGaAs rectangular wells. An example of the solution of the conduction band and the electron density distribution of a single-heterostructure GaAs/AlGaAs is also presented.

This paper presents an experimental demonstration of a basic cell of the quantum-dot cellular automata, a transistorless approach to computation that addresses the issues of device density, interconnection, and power dissipation. The device under study was composed of four metal dots, connected with tunnel junctions and capacitors, and operated at <50 mK. Operation was evidenced by switching of a single electron between output dots controlled by a single electron switching in input dots, demonstrating a nonlinear, bistable response.

We report 30-nm-gate-length InAlN/AlN/GaN/SiC high-electron-mobility transistors (HEMTs) with a record current gain cutoff frequency (fT) of 370 GHz. The HEMT without back barrier exhibits an extrinsic transconductance (g_m.ext) of 650 mS/mm and an on/off current ratio of 10⁶ owing to the incorporation of dielectric-free passivation and regrown ohmic contacts with a contact resistance of 0.16 Ω·mm. Delay analysis suggests that the high fT is a result of low gate-drain parasitics associated with the rectangular gate. Although it appears possible to reach 500-GHz fT by further reducing the gate length, it is imperative to investigate alternative structures that offer higher mobility/velocity while keeping the best possible electrostatic control in ultrascaled geometry.

We investigated two-dimensional electron transport in doped AlGaN–GaN heterostructures (with the electron sheet concentration $n_s{\text{≈10}}^{13}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-2}}$ ) grown on conducting 6H–SiC substrates in the temperature range $\text{T=0.3–300\hspace{0.17em}}\mathrm{K}.$ The electron mobility in AlGaN–GaN heterostructures grown on SiC was higher than in those on sapphire substrates, especially at cryogenic temperatures. The highest measured Hall mobility at room temperature was ${\mu }_H\text{=2019\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{2}}\mathrm{/V\hspace{0.17em}s}.$ At low temperatures, the electron mobility increased approximately five times and saturated below 10 K at ${\mu }_H\text{=10250\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{2}}\mathrm{/V\hspace{0.17em}s}.$ The experimental results are compared with the electron mobility calculations accounting for various electron scattering mechanisms.

We report on the measurements of the electron mobility in modulation-doped ${\mathrm{Al}}_{\mathrm{0.2}}{\mathrm{Ga}}_{\mathrm{0.8}}\mathrm{N–GaN}$ heterostructures grown on sapphire, conducting 6H–SiC, and insulating 4H–SiC substrates as a function of the sheet electron density, $n_s,$ at the heterointerface in a wide temperature range. The mobility increases with an increase in $n_s$ up to approximately ${\text{1×10}}^{13} {\mathrm{cm}}^{\mathrm{-2}}$ and decreases with a further increase in $n_s.$ This is explained by the electron spillover at high values of $n_s$ from the two-dimensional states at the AlGaN/GaN heterointerface into the delocalized states in the doped GaN channel. The maximum electron Hall mobility in excess of $\text{2000\hspace{0.05em}}{\mathrm{cm}}^{\mathrm{2}}\mathrm{/V s}$ at room temperature and $\text{11\hspace{0.05em}000\hspace{0.05em}}{\mathrm{cm}}^{\mathrm{2}}\mathrm{/V s}$ at 4.2 K was measured in the heterostructures grown on 6H–SiC at the values of $n_s$ close to ${10}^{13} {\mathrm{cm}}^{\mathrm{-2}}$ and ${\text{7×10}}^{12} {\mathrm{cm}}^{\mathrm{-2}},$ respectively.