Study of the thermal step signal of GaN grown on porous silicon substrate by MOVPE

In this work, we report the electric investigation of thin gallium nitride films by the thermal step method (TSM). The space charge dynamics was studied using the thermal step method with applied negative step (Δ T = −30 °C). The experimental TSM current indicates the presence of two peaks indicating the presence of two depletion widths in the silicon substrate and the GaN epilayer. The comparison between the theoretical and the measured TSM current indicates a good agreement for times less than 2 s. The divergence for times above 2 s is probably due to a thermoelectric current similar to Seebeck effect, due to the majority charge carriers’ contribution.