Quantum Hall effect in Cd$_3$As$_2$ films

A well known semiconductor Cd$_3$As$_2$ is reentering the spotlight due to its unique electronic structure of three-dimensional Dirac semimetal. We have succeeded in fabricating high crystallinity and high mobility Cd$_3$As$_2$ thin films epitaxially grown on SrTiO$_3$ to observe quantum Hall effect at high magnetic fields up to 55 T. With a decrease in film thickness to 10 nm, the quantum Hall states exhibit various changes such as of degeneracy accompanied with topological phase transitions. Detailed electronic structures of subband splitting and gap opening are identified from the quantum transport depending on the confinement thickness. Our findings and techniques pave the way for further investigation of quantum transport originating from the topological electronic structures in Cd$_3$As$_2$.