AlN插入层对AlxGa1-xN/GaN界面电子散射的影响

本文研究AlN作为Al_xGa_1-xN/GaN插入层引起的电子输运性质的变化, 考虑了Al_xGa_1-xN和AlN势垒层的自发极化、压电极化对Al_xGa_1-xN/AlN/GaN双异质结高电子迁移率晶体管(HEMT)中极化电荷面密度、二维电子气(2DEG) 浓度的影响, 分析了AlN厚度与界面粗糙度散射和合金无序散射的关系; 结果表明, 2DEG 浓度、界面粗糙度散射和合金无序散射依赖于AlN层厚度, 插入一层1–3 nm薄的AlN层, 可以明显提高电子迁移率.

Effect of inserted AlN layer on the two-dimensional electron gas in AlxGa1-xN/AlN/GaN

This paper investigates the changes of electron transport properties in Al_xGa_1-xN/GaN with an inserted AlN layer. The polarization charge density and two-dimensional electron gas (2DEG) sheet density in Al_xGa_1-xN/AlN/GaN double heterojunction high electron mobility transistors (HEMT) affected by the spontaneous polarization and piezoelectric polarization in Al_xGa_1-xN and AlN barrier are studied. Relations of interface roughness scattering and alloy disorder scattering with the AlN thickness are systematically analyzed. It is found that the alloy disorder scattering is the main scattering mechanism in Al_xGa_1-xN/GaN heterojunction high-electron-mobility transistors, while the interface roughness scattering is the main scattering mechanism in Al_xGa_1-xN/AlN/GaN double-heterojunction structure. It is also known that the 2DEG sheet density, interface roughness scattering and alloy disorder scattering are depended on the thickness of the inserted AlN layer. The 2DEG sheet density increases slightly and the mobility increases obviously by inserting an AlN layer about 1–3 nm. Taking Al mole fraction of 0.3 as an example, if without AlN layer, the 2DEG sheet density is 1.47× 10¹³ cm^-2 with the mobility limited by the interface roughness scattering of 1.15× 10⁴ cm²·V^-1·^-1, and the mobility limited by alloy disorder scattering of 6.07× 10²cm²·V^-1·^-1. After inserting an AlN layer of 1 nm, the 2DEG sheet density increases to 1.66× 10¹³cm^-2, and the mobility limited by the interface roughness scattering reduces to 7.88× 10³cm²·V^-1·^-1 while the mobility limited by alloy disorder scattering increases greatly up to 1.42× 10⁸ cm²·V^-1·^-1.