On the Superconducting Critical Temperature of Heavily Disordered Interfaces Hosting Multi-Gap Superconductivity

LaAlO3/SrTiO3 interfaces are a nice example of a two-dimensional electron gas, whose carrier density can be varied by top- and back-gating techniques. Due to the electron confinement near the interface, the two-dimensional band structure is split into sub-bands, and more than one sub-band can be filled when the carrier density increases. These interfaces also host superconductivity, and the interplay of two-dimensionality, multi-band character, with the possible occurrence of multi-gap superconductivity and disorder calls for a better understanding of finite-bandwidth effects on the superconducting critical temperature of heavily disordered multi-gap superconductors.

Investigation of Traps in AlGaN/GaN Heterostructures by Ultrasonic Vibrations

A method of dynamic deformations has been proposed as a useful informative tool in the characterization of transportation properties of a two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures. It is found that the exposing of a sample to ultrasonic vibrations results in the persistent acousto-conductivity (PAC) which was observed up to room temperatures. The PAC behaves itself like persistent photoconductivity (PPC), and the carrier density in the 2DEG channel is primarily contributed by the transfer of electrons excited from traps (like DX centers) as a result of their reconstruction under the ultrasonic loading.

Equations for the Electron Density of the Two-Dimensional Electron Gas in Realistic AlGaN/GaN Heterostructures

This paper presents equations for the electron density of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures in three realistic scenarios: (1) AlGaN/GaN heterostructure with surface exposed to ambient with mobile ions, (2) metal gate deposited on the AlGaN surface, and (3) a thick dielectric passivation layer on the AlGaN surface. To derive the equations, we analyzed these scenarios by applying Gauss’s law. In contrast to the idealistic models, our analysis shows that the 2DEG charge density is proportional to the difference between spontaneous polarization of AlGaN and GaN, whereas surprisingly, it is independent of the piezoelectric polarization.