Probe pressure dependence of nanoscale capacitance-voltage characteristic for AlGaN/GaN heterostructures

This paper investigated the effect of atomic force microscopy probe pressure on capacitance-voltage (C-V) and two-dimensional electron gas (2DEG) characteristics. Based on the experimental results, first principles and charge control model calculations were carried out to explore the origin of the changes in C-V and 2DEG characteristics. It is found that the strain of AlGaN induced by the probe pressure was very limited, thus it did not change the C-V characteristic and 2DEG density. The change of threshold voltage and 2DEG density is mainly attributed to the variation of surface barrier height, which is sensitive to the gap between the probe and the sample. Therefore, to map the electronic properties distribution, one should adopt constant force mode to eliminate the effect of probe pressure.