A quantitative analysis of photocurrent signals measured on GaAs using conductive atomic force microscopy

In this work, photocurrent (PC) spectra on GaAs measured by conductive atomic force microscope (AFM) tips are analyzed quantitatively. The measurements were carried out on n-doped bulk GaAs samples as a function of excitation wavelength and tip bias. The measured data are compared to simulations employing a two-dimensional self consistent POISSON SOLVER. It is found that the shape of the depletion zone below the AFM tip is strongly influenced by the tip bias and the surface potential, which leads to a clear difference between PC data obtained with large area devices and conductive AFM tips.