Effects of Al addition to Si-based flux on the growth of 4H-SiC films by vapour-liquid-solid pulsed laser deposition

The stabilizing effect of Al addition to Si-based flux on 4H-type SiC has recently become a well-known phenomenon as it is commonly found in solution growth for bulk wafer use and in the vapor-liquid-solid (VLS) mechanism for epitaxial thin films. To understand its mechanism, in this study, we investigated the Al additive effects on VLS pulsed laser deposition (PLD) of SiC films on 4° off 4H-SiC (000-1) substrates, systematically varying the Al content in the Si flux. The inclusion of 3C-type SiC in the films tended to decrease as the Al content in the flux increased. On the other hand, a sizable amount of Al, ∼10²⁰ cm^-3, was necessarily incorporated as a dopant homogeneously into the SiC films, giving a good linear relationship between the Al density in the SiC films and the Al content in the flux. In situ observation of a flux/SiC growth interface with a confocal laser scanning microscope technique revealed that the Al addition induced a well-regulated step-flow growth even at a temperature as low as 1300 °C, which is favoured for the selective growth of the 4H-type SiC, succeeding to the 4H stacking sequence of the seed substrate.