Evolution of Electrically Active Defects in n-GaN During Heat Treatment Typical for Ohmic Contact Formation

Ohmic contact formation to n-type GaN often involves high temperature steps, for example sintering at about 800 degrees C in the case of Ti-based contacts. Such processing steps might cause changes in the distribution, concentration, and properties of the defects. The present work aims at contributing to the knowledge about defect evolution in GaN upon processing at different temperatures. The processing temperatures are selected according to fabrication procedures for commonly used ohmic contacts to n-GaN: 300 degrees C (In-based), 550 degrees C (Ta-based), and 800 degrees C (Ti-based). Properties and concentration of the defects are studied by the means of deep level transient spectroscopy (DLTS). Changes in carrier capture kinetics are monitored with varying filling pulse duration.