The effects of passivation and temperature on the barrier strain of Al0.22Ga0.78N/GaN heterostructures
表面钝化前后Al0.22Ga0.78N/GaN异质结势垒层应变的高温特性

The barrier strain in Al0.22 Ga0.78 N/GaN heterostrueture, with and without Si3N4 passivation layer, was investigated at temperatures from room temperature to 813K by using high resolution X-ray diffraction. The strain relaxation occurs when the temperature exceeds 523K for the unpassivated Al0.22 Ga0.78 N layers. After passivation, an initial increase of the strain with increasing temperature is observed in Al0.22 Ga0.78 N layers, and at the higher temperatures the strain only decreases slightly in the 100-nm-thick Al0.22Ga0.78 N layer, but a pronounced strain relaxation occurs in the 50-nm-thick one due to the fact that the thickness of the Al0.22 Ga0.78 N layer is close to the critical thickness, and hence the increase of tensile strain induced by passivation will result in partial strain relaxation via the formation of cracks or the gliding motion and multiplication of dislocations.