Humidity-dependent stability of amorphous germanium nitrides fabricated by plasma nitridation

We have investigated the stability of amorphous germanium nitride ( Ge 3 N 4 ) layers formed by plasma nitridation of Ge(100) surfaces using x-ray photoelectron spectroscopy and atomic force microscopy. We have found that humidity in the air accelerates the degradation of Ge 3 N 4 layers and that under 80% humidity condition, most of the Ge-N bonds convert to Ge-O bonds, producing a uniform Ge O 2 layer, within 12 h even at room temperature. After this conversion of nitrides to oxides, the surface roughness drastically increased by forming Ge O 2 islands on the surfaces. These findings indicate that although Ge 3 N 4 layers have superior thermal stability compared to the Ge O 2 layers, Ge 3 N 4 reacts readily with hydroxyl groups and it is therefore essential to take the best care of the moisture in the fabrication of Ge-based devices with Ge 3 N 4 insulator or passivation layers.