Study of cracks formation in HIGHLY – low boron-doped epitaxial (113) diamond bilayers

Abstract

In this work, we present the study of the formation of cracks in high and low boron-doped diamond epitaxial bilayers necessary in the fabrication process of Schottky diodes. Epitaxial diamond layers were grown on (113) oriented diamond substrates by Microwave Plasma Enhanced Chemical Vapor Deposition. The effect of the thickness and the methane concentration during the growth of the undoped diamond layer on the crack formation have been studied using optical and scanning electron microscopy (SEM). We experimentally observed a critical thickness of ca. 3.5 µm above which all undoped layers are cracked. The formation of these cracks is attributed to the relaxation of the elastic energy stored in the epitaxial undoped layer due to the significant lattice mismatch (ca. 0.8 %) between the undoped and highly boron-doped diamond layers with a boron concentration of 10 21 cm -3 as determined by Raman spectroscopy analysis.