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 °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 °C (In‐based), 550 °C (Ta‐based), and 800 °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. The figure shows DLTS spectra of the samples treated at the different temperatures (300 oC, 550 oC, 800 oC). The heat treatment influences the properties and concentration of electrically active defects: E1 change in activation energy, E2/E3 steady increase in concentration upon annealing; E4 decreases while E5/E5 become pronounced.