Local increase in compressive strain (GaN) in gate recessed AlGaN/GaN MISHFET structures induced by an amorphous AlN dielectric layer

Abstract

We fabricated and characterized metal insulator semiconductor (MIS) structures by applying amorphous AlN thin layers as a dielectric in gate recessed AlGaN/GaN heterostructure field effect transistors (HFETs). Micro photoluminescence measurements performed on MISHFET devices reveal a local non-uniform distribution of strain in the source—gate recess—drain region. Furthermore, a reduction of compressive stress up to 0.3 GPa in GaN after gate recessing was experimentally determined. The local stress increases by ∼0.1 GPa and ∼0.2 GPa after the deposition of 4 and 6 nm thin AlN layers in the gate recessed structures, respectively. Additionally, an increase in sheet charge density in the devices under investigation from ∼ 3.8×1012cm−2\u2009 to ∼ 6.2×1012cm−2\u2009 was evaluated by capacitance–voltage measurements. Therefore, strain engineering by applying amorphous AlN layers in gate recessed MISHFETs can significantly improve their device characteristics.