Characterization of heterojunction devices constructed by amorphous diamondlike films on silicon

• Published in: Journal of applied physics 1997-05, Vol.81 (9), p.6238-6245
• Main Authors: Konofaos, N., Thomas, C. B.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.364412

The electronic properties of amorphous diamondlike carbon (DLC) films on silicon were examined for their capability for application to electronic devices. Metal-insulator-semiconductor (MIS) diodes and p-n heterojunction devices were created and characterized. The films used were grown using rf plasma assisted CVD of methane. They were grown on n-type silicon (100) wafers. Their structural composition was identified by Raman spectroscopy, ellipsometry, and x rays. They showed an insulating behavior and they were suitable for the creation of MIS devices. They showed extremely low internal conductivity due to defect currents. This conductivity showed a behavior of the form I∼T1/4. Then the density of trapping states at the silicon/carbon interface was measured using the conductance technique. The aim of investigating the nature and behavior of these states was to determine the magnitude of the density of states and try to find a way to reduce it. Thus optimization of the DLC/silicon interface could be made, for future reference to the construction of heterojunction devices containing the DLC/silicon configuration. The values of the density of states were of the order of 1011–1012 cm−2 eV−1. Annealing had the effect of reducing the magnitude of the Dit. The ion implantation technique was used to transform the insulating DLC films into semiconducting by adding boron ions as dopants to achieve p-type conductivity. Thus p-n heterojunction devices were made, having silicon as one of the elements and DLC as the other element. Four different doses of boron were implanted, producing different conducting properties of the DLC films. Those devices performed like Schottky diodes for low boron doses and like p-n diodes for high doses.