Poole–Frenkel emission and bulk charge trapping in AlON deposited on GaN and comparison to Al2O3

Abstract

The leakage conduction mechanisms in AlON dielectric deposited on GaN are identified and compared to the findings for Al2O3. Poole–Frenkel emission from similar trap energy levels was identified in both atomic layer deposited AlON and Al2O3¸ despite at different electric field ranges, while Fowler–Nordheim tunneling dominated the leakage current characteristics for Al2O3 at average electric field values. It is concluded that the differences observed in the leakage characteristics for these dielectrics are likely a result of the slightly larger conduction band offset between AlON and GaN. The identification of the same trap state energy level responsible for Poole–Frenkel emission in AlON and Al2O3 means that this trap state does not originate from the presence of nitrogen in the dielectric and is related to AlOx compounds and the deposition method. Bulk charge trapping is shown to play a major role in the leakage characteristics of AlON from average to high electric fields, which shifts the transfer characteristics from a certain electric field onward and causes hysteresis. These results provide valuable insights into the development of insulated gate architectures on GaN using the promising dielectric material AlON as the gate oxide.