Investigation of MOCVD grown crack-free 4 μm thick aluminum nitride using nitrogen as a carrier gas

We report the growth of crack-free 4 μm thick Aluminum Nitride (AlN) layers in a custom build vertical cold wall metal–organic chemical vapor deposition (MOCVD) reactor using N2 carrier gas on 0.2° offcut sapphire substrate without any additional substrate preprocessing steps. The growth process includes a low-temperature pulsed rough buffer layer followed by a high-temperature layer with continuous growth without any interlayer. The structural properties of the AlN were analyzed using atomic force microscopy (AFM), X-ray diffraction (XRD), and Raman spectroscopy. The AFM image of the 4 µm AlN layer shows an atomically smooth 2-dimensional surface with terrace-like steps. The dislocation density of 1 × 109 cm−2 was calculated using Williamson and Hall process for a 4 µm AlN sample. Additionally, strain calculation from XRD and stress calculation from Raman spectroscopy of AlN grown with N2 carrier gas are discussed.