Growth of Diamond within the Trenched AlN Surface and Study of the Induced Stress.

Diamond has been successfully grown within a patterned and trenched Aluminum Nitride (AlN) thin film using hot filament chemical vapor deposition. The ICP-RIE plasma etching process was used to form the trenched AlN-on-Si (111). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and thermal modeling with the COMSOL Multiphysics tools were used to examine the structural and morphological characteristics of the heterostructure. Even though the initial intention was to have a coating of polycrystalline diamond on the bottom of the etched trenches, it was revealed that the diamond also extended along the trench sidewalls as well as laterally on a portion of the AlN surface. This resulted in the creation of a vertical interface heterojunction, which holds promise for application in heterogenous integration of Ultra-Wide Bandgap (UWBG) semiconductor devices. The contact between vertical and horizontal AlN/diamond components appears seamless when observed in TEM micrographs. The Full Width at Half Maximum (FWHM) of the AlN (0002) diffraction peak and its rocking curve were unchanged after diamond deposition, indicating the integrity of the AlN. Based on the change in the Raman spectra's position from the free-standing substrate, the biaxial stress in the thin films was calculated. Finite Element analysis corroborates the experimental findings and demonstrates that the developed stress on the layer is due to the mismatch in the Coefficients of Thermal Expansion (CTE) of the materials.