We study the transport properties of a GaAs-based semiconductor under local optical excitation via direct numerical simulation. The simulation results propose a hypothesis which describes the possibility to control the high-field domain in terms of tunable modulations of the doping profile and the length of the notch region. This hypothesis can be verified, both quantitative and qualitative agreement, via principal-component analysis. Besides, higher harmonic modes embedded in the high-field domain also can be automatically extracted from principal-component analysis. This study might be useful to identify the "effective" length and shape of the cathode notch and to restore the doping concentration in semiconductor devices. (c) 2005 Elsevier Ltd. All rights reserved.