Inp/langmuir-film m.i.s.f.e.t.

Abstract

The electrical properties of m.i.s. structures based on indium phosphide and organic films deposited using the Langmuir-Blodgett technique have been investigated. A strongly inverted low-frequency C/V response occurs at approximately 30 Hz using both melt-grown InP single crystals and epitaxial layers of this material prepared using the vapour-phase technique. Interface state distributions have been evaluated from the admittance data using quasistatic and conductance techniques. For an n-type InP-epitaxial-wafer/cadmium-stearate junction, the effective surface-state density is found to be ~3×1011 cm−2 eV−1 over a large fraction of the bandgap. Average surface-state densities calculated for structures based on melt-grown crystals were approximately one order of magnitude higher. For the first time measurements are reported for a transistor incorporating a Langmuir-Blodgett film. From the transfer characteristics of this relatively simple depletion-mode device, the InP field-effect surface mobility is calculated to be 2250 cm2 V−1 s−1