Epitaxial aluminum on hybridized InAs/GaSb quantum wells

Hybridized InAs/GaSb quantum wells (QW) are approved the existence of helical edge channels. According to the theoretical prediction, the combination with superconductor will lead to superconducting topological phase and realization of Majorana bound state (MBS). Besides, InAs/GaSb material shows a low Schottky barrier to superconductor, and high quality of superconductor-topological insulator interface will result in hard induced gap. In recent report [1], under low temperature of substrate, there is a good lattice match between InAs naowire and Al in the same direction. In our lab, we perform aluminum epitaxy on the in-situ cleaved InAs/GaSb QW with similar methods in our ultra-high vacuum STM system. After metal epitaxy, the Al layer can be selectively etched for fabricating the superconductor-topological insulator junction devices. [1] P. Krogstrup, N. L. B. Ziino, W. Chang, S. M. Albrecht, M. H. Madsen, E. Johnson, J. Nyg{\aa}rd, C. M. Marcus, T. S. Jespersen, Nature Materials 14, 400 (2015).