Growth and characterization of epitaxial SrF2 on InP(100)

Abstract

Indium phosphide is an important substrate material for microwave metal–insulator–semiconductor field effect transistor (MISFET) devices; SrF2 is an attractive candidate for use as an insulating layer on it because of the relatively close lattice match (−1.2% mismatch). We have grown epitaxial SrF2 films on n-type and p-type InP(100) surfaces using a conventional UHV system. The combination of a brief ion bombardment at 350 °C using 0.5 keV argon ions and a subsequent anneal at the same temperature was found to be an effective cleaning technique for the InP(100) substrate that was chemicomechanically polished prior to insertion in the UHV chamber. The best quality epifilms were grown at 350 °C, using a slow (<1 Å/s) initial growth rate, with a postanneal at the same temperature. The substrate and the film surfaces were characterized in situ, using low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES), and ex situ, using reflection high-energy electron diffraction (RHEED) and Nomarski optical microscopy. In this paper we report these results, along with the results of capacitance–voltage (C–V) measurements on these films.