Superconductor-topological insulator junctions based on an Sb₂Te₃/Bi₂Te₃ p-n heterostructure

Topological insulators combined with superconducting electrodes are very promising systems for realizing Majorana bound states. However, realizing functional structures including 3D topological insulator (TI) materials suffer from a high unintentional background doping as well as surface state degradation due to oxygen inclusion as soon as the sample is exposed to air. Here, we present the successful integration of niobium superconducting contacts on top of a 3D TI layer system. The TI layers were grown by means of molecular beam epitaxy on Si (111) substrates and are capped in-situ by a few nm of aluminumoxide to protect the Dirac-like surface states. Utilizing a layer stack of p-type doped Sb2Te3 on top of n-type doped Bi2Te3, defining a p-n heterostructure, pushes the Fermilevel at the upper surface to the Dirac-point.