Evaluate Fixed Charge and Oxide Trapped Charge on SiO₂/GaN MOS Structure Before and After Post Annealing

Abstract

The electrical properties of SiO2/GaN metal‐oxide‐semiconductor capacitors with different SiO2 thicknesses are evaluated before and after postmetallization annealing (PMA). The distribution of charges in bulk SiO2 and the SiO2/GaN interface is estimated by analyzing the electrical properties. It is revealed that the net effective charges (Nf) tend to increase with decreasing SiO2 thickness before PMA. This indicates that the negative bulk charges are present uniformly, and the positive interface charges exist locally near the interface. In the sample after PMA, Nf tends to decrease with decreasing SiO2 thickness at the thin SiO2 region (<25 nm). This indicates that the distribution width of positive charges becomes larger by applying PMA. Therefore, PMA widens the distribution of interface positive charges, although it is effective in reducing the amount of Nf.

Influence of the Cl2 etching on the Al2O3/GaN metal–oxide–semiconductor interface

“…Nevertheless, these works demonstrate an additional positive dipole strength that cannot explain the observed opposite variation of the Vfb. On the other hand, the formation of SiOx/GaN generates positive charges which, in turn, causes a negative flat band voltage shift 24,25 .…”