Correlating stress generation and sheet resistance in InAlN/GaN nanoribbon high electron mobility transistors

Abstract

We report the nanoscale characterization of the mechanical stress in InAlN/GaN nanoribbon-structured high electron mobility transistors (HEMTs) through the combined use of convergent beam electron diffraction (CBED) and elastic mechanical modeling. The splitting of higher order Laue zone lines in CBED patterns obtained along the [540] zone axis indicates the existence of a large strain gradient in the c-direction in both the planar and nanoribbon samples. Finite element models were used to confirm these observations and show that a passivating layer of Al[subscript 2]O[subscript 3] can induce a tensile stress in the active HEMT layer whose magnitude is dependent on the oxide layer thickness, thus, providing important ramifications for device design and fabrication.