High barrier height, low leakage current Schottky contacts to III-V semiconductors are important for application to field effect transistors, optical sensors and photovoltaic converters. Schottky contacts to III-V semiconductors will be cryogenically processed (CP) to greatly increase barrier height and reduce leakage current. Specific semiconductor materials will include n-type InP, GaAs, InAlAs and IngaAs. Diodes will be fabricated with the substrate cooled to 77K, a process which already has given promising results in the form of increased barrier height, to 0.96 eV in n-InP, and reduced leakage current by several orders of magnitude. The metals Al, Cu, Au, Pd and Pt will be utilized to show unpinning of the Fermi level. An important aspect of the study involves understanding the reason for CP contacts to give such improved performance. Electrical and optical data will be correlated with high resolution structural and chemical data. Electrical and optical data will include current-voltage-temperature to reveal conduction mechanisms, deep level transient spectroscopy, photoreflectance spectroscopy, photoreflectance spectroscopy, and Raman spectroscopy. High resolution transmission electron microscopy and chemical analysis will be correlated with other data. A later focus will be made to apply the CP technique to quantum well and superlattice structures, where extremely sharp interfaces are of great importance.
