An Improved Fabrication Method for Van Der Pauw Mobility Measurement on GaN Epitaxy on Conductive and Non-Conductive Substrates

A novel empirical method for fabricating Van der Pauw Hall test samples on GaN epitaxy is proposed and tested, which enables rapid preparation of Van der Pauw Hall test samples on both conductive and non-conductive substrates. Compared to traditional Van der Pauw Hall sample preparation, this approach eliminates the need for annealing to form Ohmic contacts, thereby facilitating more accurate measurement of the resistivity, Hall coefficient, majority carrier concentration, and mobility in semiconductor wafers, which may be subject to change after high-temperature annealing. This method is based on the use of specialized plasma dry-etched patterns to form the Ohmic electrodes, which reduces the metal–semiconductor contact barrier, allowing the tunneling current to dominate and thus forming Ohmic contacts. In the validation experiments, three different substrate materials for GaN-epi—silicon, sapphire, and silicon carbide—were selected for the preparation of the Van der Pauw Hall test samples, followed by testing and analysis to confirm the accuracy of the new test method. The measurement results for the electron mobility and carrier concentration on the sapphire and silicon carbide substrate samples were verified via the contactless RF reflectance mapping method, with an average difference only 4.0% and 7.0%, respectively, and a minimum of only 0.53% and 1.8%. The proposed fabrication method features a relatively simple structure, enabling rapid preparation and avoiding the damage and errors caused by high-temperature annealing processes. It shows great potential for industrial application on precise carrier property measurements, especially for GaN-epi on a conductive substrate.