The influence of the Franz-Keldysh effect on the electron diffusion length in p-type GaN determined using the spectral photocurrent technique

The zero-bias spectral response of a p-type GaN Schottky diode with an acceptor doping density of 10(19) cm(-3) was measured, and the electron diffusion length was calculated using the standard theoretical equation that relates this parameter to the measured photocurrent. Here it is shown that the minor but perceptible spectral variation of the diffusion length calculated can be explained by taking into account the Franz-Keldysh effect. Consideration of this effect, through the use of an equation that describes the electric field and spectral dependence of the absorption coefficient, leads to a constant diffusion length value of 14 nm. By also taking into account the inherent inaccuracy of the theoretical equation, a final value of 10 nm was estimated for the electron diffusion length. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4746740]