The effects of size and strain on the electronic behavior of AlN/GaN heterojunction

The electronic behavior of AlN/GaN heterojunction is investigated at thicknesses of 1.2~4.2 nm and biaxial strain of -8%~8% based on density functional theory. The structural stability, charge distribution, electronic properties, and transport properties of the cells reveal the enhancing effects of size and strain. With the thickness decreases, the bandgap values of the cells, as low as -0.387 eV, confirm the transition in structural nature, while the individual atomic layers remain bandgaps of at least 0.3 eV in DOS. The carrier mobility enhances to 2×1012 m2/V/s. The cell with 1.2 nm thickness is weakened by 50% due to the quantum confinement effect. Under compressive strain ranging from -8% to 0%, the characteristics of heterojunctions are enhanced by an order of magnitude, in contrast, under 0%~8% tensile strain, the cells decrease slightly but for 2L cells.

本研究基于密度泛函理论（Density Functional Theory），系统探究了厚度区间为1.2~4.2 nm、双轴应变范围为-8%~8%的AlN/GaN（氮化铝/氮化镓）异质结的电子行为。研究对象的结构稳定性、电荷分布、电子特性及输运特性均表明，尺寸与应变对该异质结性能存在显著增强效应。随着厚度降低，晶胞的带隙值可低至-0.387 eV，证实了其结构性质发生转变；而在态密度（Density of States, DOS）分析中，单个原子层的带隙仍至少保持0.3 eV。载流子迁移率提升至2×10¹² m²/(V·s)。厚度为1.2 nm的晶胞因量子限域效应，其性能被削弱了50%。当处于-8%~0%的压应变区间时，异质结的特性提升了一个数量级；与之相反，在0%~8%的拉应变区间下，除双层（2L）晶胞外，其余晶胞的性能均出现小幅下降。