Fluoride dielectric films on inp for metal-insulator-semiconductor applications

Abstract

This paper describes the characteristics of thin fluoride films on InP which are used as dielectric for metal-insulator-semiconductor (MIS) devices. Films of Ba_1-xSr_xF₂ (x=0.0, 0.5, 0.83, and 1.0) were deposited by sublimation of mixtures of BaF₂ and SrF₂ in vacuum under 10^-5 Torr pressure. The composition of the films was deduced from x-ray diffraction and energy dispersion analysis by x-ray studies. The electrical activation energies of the films determined between 120 and 300 K were found to be 3.5-22.0× 10^-3 eV , depending on composition and temperature. The resistivity of the films was in the range of 5.0× 10¹¹ to 5.0× 10¹² Ωcm with the breakdown fields greater than 5.0× 10⁵ Vcm^-1 . The interface state density obtained was as low as 5× 10¹⁰ cm^-2eV^-1 with annealed BaF₂ films. Scanning electron microscope studies showed that annealing caused development of cracks resulting in decreased film resistivity. Auger studies gave evidence of broadening of the interface and outdiffusion from the substrate due to annealing.