Gas source chemical vapor deposition of hexagonal boron nitride on C-plane sapphire using B2H6 and NH3

Abstract

Chemical vapor deposition (CVD) of hexagonal boron nitride (hBN) using diborane (B2H6) and ammonia (NH3) is reported. The effect of growth conditions on hBN growth rate using continuous vs. flow modulation epitaxy (FME) method is investigated to gain insight into the role of gas-phase chemistry during film deposition. In continuous mode, hBN growth rate decreases with increase in growth temperature, reactor pressure, and decrease in gas velocity. This is attributed to increased gas-phase polymerization of intermediate products such as borazine (B3N3H6) which forms high molecular weight species that do not contribute to hBN film growth. Using FME method, the hBN growth rate increases by ~ 25 times compared to continuous mode and exhibits a strong positive dependence on substrate temperature with an activation energy of ~ 61.1 kcal/mol, indicative of a kinetically limited process. The results provide additional insight into the effects of gas-phase reactions on CVD of hBN. Graphical abstract: [Figure not available: see fulltext.]