Electroreflectance And Photoreflectance Characterization Of The Space Charge Region In Semiconductors: Ito/Inp As A Model System

Abstract

We have investigated the electroreflectance (ER) and photoreflectance (PR) spectra from the space charge region (SCR) of the model Schottky barrier system indium-tin-oxide on p-InP (ITO/InP). Both ER and PR were studied as a function of reverse dc bias, V_bias. The observed Franz-Keldysh oscillations (FKO) provide a direct measure of the surface dc electric field, εsdc. In ER the ac modulating voltage (for small modulation) effects only the envelope of the FKO but not the period. A generalized Franz-Keldysh theory, taking into consideration large built-in dc fields, is presented which accounts for the above experimental results. From a plot of (Eac)2 as a function of Vbias we have obtained the built-in potential and net carrier concentration of the device. Our work demonstrates that electromodulation in Schottky barriers can be used as an optical Mott-Schottky method.