Correlation between current–voltage characteristics and dislocations evaluated with submicrometer Schottky contacts on n-GaN grown by metalorganic chemical vapor deposition

We directly evaluated the effect of dislocations on current–voltage (I–V) characteristics of Au/Ni contacts formed on n-GaN grown by metalorganic chemical vapor deposition. The key feature of our evaluation is the combination of submicrometer Schottky dot array formation by electron-beam lithography and I–V measurement by atomic force microscopy with a conductive probe. The sample, which has a free electron concentration of 3×1017 cm−3, showed that neither mixed nor pure edge dislocations affect the I–V characteristics (Schottky barrier height, ideality factor, and reverse leakage current). Possible models to explain the results are discussed. On the other hand, it was found that a large structural defect with a diameter of a few hundred nanometers shorted the contact. The density, however, was less than 4×105 cm−2. These results indicate that, in fabricating short-gate field-effect transistors, gate Schottky contacts containing dislocations should not be considered a problem with respect to uniformity and reproducibility.