Study of the leakage current mechanism in Schottky contacts to Al_(0.25)Ga_(0.75)N/GaN heterostructures with AlN interlayers

摘要

The leakage current mechanism in Schottky contacts (SCs) to Alo.25Gao.75N/GaN heterostructures incorporated by a thin high-temperature (HT) A1N interlayer has been investigated using current-voltage measurements, atomic force microscopy and deep level transient spectroscopy. It is found that the HT A1N interlayer thickness has a significant effect on the leakage current in SCs. The leakage current density decreases to 1.1 × 10~(-4) A cm~(-2) when the growth time of the A1N interlayer increases from 0 to 10 s, and then changes to increase with increasing growth time. Correspondingly, the heterostructure with the A1N growth time of 10 s has the least number of surface pinholes. The thickness of the HT A1N also influences the density of electron traps with the activation energy of 0.762 eV in an Al_(0.25)Ga_(0.75)N barrier. It is suggested that the HT A1N interlayer adjusts the microstructure and the defect state density in the Al_(1-x)Ga_xN barrier, and the leakage via these defect states makes the main contribution to the leakage current in SCs to Al_(1-x)Ga_xN/GaN heterostructures.