No abstract

Herein, the physical mechanism of the GaN interlayer for improving 2D electron gas (2DEG) mobility in the InGaN channel using an intersub‐band scattering model is systematically elucidated. The model takes into account various scattering mechanisms between the first four sub‐bands, in which the wavefunction of each sub‐band is obtained by self‐consistently solving 1D Schrödinger−Poisson equations. The total 2DEG mobility is obtained by averaging the sub‐band mobility by the percentage of electrons in the different sub‐bands. The effect of introducing different thicknesses of the GaN interlayer on the mobility limited by various scattering mechanisms is discussed in detail, especially polar optical phonon scattering and alloy disorder scattering. The calculated results are well supported by the reported experimental data, validating the correctness of the model.

The authors simulated the damage caused by proton irradiation to the device and analyzed the effect of proton irradiation on two-dimensional electron mobility taking various scattering mechanisms into account. Proton-irradiation simulation of the AlGaN/AlN/GaN HEMT device was carried out to obtain the irradiation simulation results by using SRIM software. Then, considering various scattering mechanisms, the authors established a model to simulate two-dimensional electron mobility under different proton energy and irradiation doses at low temperature. The theoretical data show that proton irradiation significantly decreased the mobility of a two-dimensional electron in a GaN-based HEMT at low temperature.

2D/3D heterostructures have received extensive attention due to their unique structures and outstanding properties. In this work, the structural and electronic properties of monolayer MoS2/4H-SiC(Si-face) heterojunctions are systematically investigated through density functional theory calculation and experimental analysis. The calculated results show that the monolayer MoS2/4H-SiC heterostructure is a van der Waals heterojunction because of low formation energy and shows a type-II band alignment with a valence band offset of 1.43 eV. Then the type-II band alignment of the MoS2/4H-SiC heterostructure is verified by x-ray photoelectron spectroscopy. However, there is a deviation of 0.44 eV in the valence band offset between the calculated results and the experimental data, which may be caused by the underestimation of the bandgap by the Perdew–Burke–Ernzerhof method and the introduction of impurities at the interface. Our experimental results reveal the type of band alignment and the combination of the MoS2/4H-SiC heterostructure interface, which is an effective way to understand and design photocatalysts and electronic devices.

Gallium nitride (GaN)-based high electron mobility transistors (HEMTs) that work in aerospace are exposed to particles radiation, which can cause the degradation in electrical performance. We investigate the effect of proton irradiation on the concentration of two-dimensional electron gas (2DEG) in GaN-based HEMTs. Coupled Schrödinger’s and Poisson’s equations are solved to calculate the band structure and the concentration of 2DEG by the self-consistency method, in which the vacancies caused by proton irradiation are taken into account. Proton irradiation simulation for GaN-based HEMT is carried out using the stopping and range of ions in matter (SRIM) simulation software, after which a theoretical model is established to analyze how proton irradiation affects the concentration of 2DEG. Irradiated by protons with high fluence and low energy, a large number of Ga vacancies appear inside the device. The results indicate that the ionized Ga vacancies in the GaN cap layer and the AlGaN layer will affect the Fermi level, while the Ga vacancies in the GaN layer will trap the two-dimensional electrons in the potential well. Proton irradiation significantly reduced the concentration of 2DEG by the combined effect of these two mechanisms.