Investigation of breakdown mechanism during field emission process of AlN thin film microscopic cold cathode

Abstract

The breakdown mechanism of a 100 nm-thick AlN thin film cold cathode structure was investigated during the field emission process, where the AlN film was synthesized by metalorganic chemical vapor deposition under low pressure on an n-type SiC substrate. The microdevice structure formed by a Si-doped AlN film (NSi = 1.0 × 1018–1.0 × 1019 cm−3) and by an unintentionally doped AlN film were first characterized by a field emission (FE) system in a vacuum chamber. During the measurement, the FE current of those two samples presented an discontinuous increase with increasing voltage, and ultimately a breakdown of current with an abrupt drop-down (around 1 × 10−6 A). Scanning electron microscopy coupled with energy dispersive spectral analysis was applied to characterize the surface morphology and chemical elements of the Si-doped AlN film surface after the FE measurement. Nonuniform local field enhancement factors of the AlN film was proposed to explain the fluctuation increase in the FE current with increasing electric field. It was believed that both heat accumulation in the cathode and the bombardment of Au ions sputtered from the anode are responsible for the breakdown of the FE characteristics of the AlN cold cathode.