Effects of the growth temperature on structural and electrical properties of AlN/GaN heterostructures grown by metal organic chemical vapor deposition

Abstract

In this paper, we present the dependence of structural and electrical properties of AlN/GaN heterostructure on the growth temperature on sapphire substrates by metal organic chemical vapor deposition. The results revealed that higher Ga incorporation (similar to 47%) and higher trench density on the surface of AlN barrier layer when grown at 1125 degrees C. However, further decreasing the AlN growth temperature to 500 degrees C results in the lower Ga incorporation (similar to 5%), higher dislocation density, 3D island growth and larger tensile strain of AlN barrier layer. Degradation of structural properties and surface morphologies AlN barrier layer results in the higher resistivity of 2-dimensional electron gas transport properties. Low sheet resistance (255.45 Omega/sq), high free carrier electron density (2.86 x 10(13) cm(-2)), simultaneously maintaining low surface roughness and high crystal quality of AlN barrier were achieved at optimized growth temperature around 800 degrees C.