Analysis of strain induced carrier confinement with varying passivation thickness of the Al0.3Ga0.7N/GaN heterostructure with graded AlxGa1-xN buffer on Si (111) substrate

Abstract

In this study, the authors demonstrate the strain induced piezoelectric charge effect on carrier confinement at the Al0.3Ga0.7N/GaN heterointerface with varying passivation (Si3N4) thicknesses. The graded Al0.2Ga0.8N/Al0.1Ga0.9N buffer on the Si (111) substrate grown by plasma assisted molecular beam epitaxy reduces the dislocation density of the GaN layer, which significantly improves the carrier concentration at the Al0.3Ga0.7N/GaN interface. The carrier confinement as well as the two-dimensional electron gas (2DEG) density with varying passivation thicknesses has been investigated through high resolution x-ray diffraction (HRXRD) followed by strain analysis and capacitance–voltage (C-V) measurements. As per the HRXRD strain analysis, the 2DEG density was predicted to increase about 5%, 7.9%, and 10% after Si3N4 passivation of 20, 30, and 40 nm, respectively. This enhancement in carrier density (2DEGs) was then validated by C-V characteristics for the same Si3N4 variation. After passivation, the induced tensile strain on the Al0.3Ga0.7N barrier along with surface state reduction at the interface of Si3N4/Al0.3Ga0.7N effectively improves the carrier confinement at the Al0.3Ga0.7N/GaN interface.