表面电荷密度及介电常数对AlGaN/GaN异质结中二维电子气性质的影响

Effect of surface charge density and dielectric constant on the twodimensional electron gas properties in AlGaN/GaN heterojunctions

通过在Al_(x)Ga_(1-x)N层引入离化电荷面密度,结合自发极化和压电极化引起的极化电荷面密度,利用变分法计算二维电子气面密度随Al组分和Al_(x)Ga_(1-x)N厚度的变化关系.研究了相对介电常数对电子气密度的影响,并与实验数据进行了比较.通过在Al_(x)Ga_(1-x)N的相对介电常量中引入高阶项,使得计算结果更好地拟合了高Al组分的电子气密度.计算得到的离化电荷面电荷密度与极化电荷面电荷密度相当,从而证明离化面电荷密度对二维电子气形成的贡献.

By introducing the surface state in the outer layer of Al_(x)Ga_(1−x)N heterostructure and incorporating the electric polarization density induced by spontaneous and piezoelectric polarization,we use the variational method to analyze how Al composition and the thickness of Al_(x)Ga_(1−x)N affect the surface density of the twodimensional electron gas,comparing the results with the experimental data.Additionally,we investigate the impact of the relative dielectric constant on the two-dimensional electron gas density,introducing a higherorder term in the relative dielectric constant of Al_(x)Ga_(1−x)N,to improve the fit with the electron gas density at high Al compositions.Surface density calculations are also performed,and the results are compared with the polarization charge density to demonstrate the contribution of surface charge density to the formation of the two-dimensional electron gas.