In this paper? we studied the structural transformation of screw dislocatio
ns through gas-phase 4H-SiC epitaxial growth. We confirmed based on the num
bers and features of etch pits on a surface after KOH treatment that some m
icropipes were closed in the epitaxial layer, and were divided into several
elementary screw dislocations. We discuss the magnitude of Burgers vectors
of micropipes in 4H-SiC substrates in relation to the number of elementary
screw dislocations generated by micropipe closing. A depth analysis furthe
r revealed that most micropipe closings tool; place in the initial stage of
epitaxial growth.