Characterization of interface charge at Ga0.52In0.48P/GaAs junctions using current–voltage and capacitance–voltage measurements

Abstract

Al/i:GaInP/n:GaAs Schottky structures of varying undoped layer thicknesses (100–1000 Å) were grown in situ by gas source molecular beam epitaxy (GSMBE). Effective Schottky barrier heights (φbIV)of 0.87±0.02 eV were determined from the current–voltage (I–V) method with ideality factor of <1.05 which is characteristic of thermionic emission but a decrease in barrier height (φbCV) with increasing GaInP thickness as measured by the capacitance–voltage (C–V) method was observed. We found that the plot of φbIV minus φbCV versus GaInP thickness is a straight line. This can be explained by modeling a positive delta sheet charge at the GaInP/GaAs interface which will result in a constant electric field (slope of the above line) with sheet charge estimated to be 5×1011 cm−2. This sheet charge is proposed to be the result of ionized donor states at such interface.