Electrical and optical properties of a polymer semiconductor interface

We have fabricated a stable electrical interface between a range of n-type, p-type and undoped GaAs epitaxial layers and a film of conductive p-type polyaniline. The IV characteristics of this device show rectifying behaviour consistent with a potential barrier formed at the interface. We have used simple thermionic emission theory for a Schottky type barrier to model the results. This has shown no significant change in the barrier height as the fermi level moves through the semiconductor bandgap by changing from n-type to p-type substrates. We have measured the temperature dependence of the barrier height. Using n-type GaAs we can observe electroluminescence centred at 680 nm with a FWHM of 160 nm at a current density of 5 mA cm−2. Our data suggests that the interface characteristics are controlled by surface states on the GaAs layer.