On the p-type character of Cd-and Zn-doped InAs nanowires

InAs nanowires are potential materials for high speed nanoelectronic devices due to their high electron mobility among the semiconductor nanostructures. One of the main challenges, however, is to obtain a p-type InAs material, since the Fermi level is usually pinned at the conduction band, leading to an intrinsic n-type behaviour. Here we show through first principles calculations that InAs nanowires, doped with Cd or Zn substitutional impurities, can behave as p-type materials. Differently from other III-V nanowires, these impurities introduce shallow acceptor levels. We show that the Zn impurity can be equally distributed along the nanowire radius, naturally compensating the surface levels. On the other hand, the Cd impurity is preferentially found in the core region, requiring a surface treatment to eliminate the surface pinning levels. These results explain the available experiments and show how and why p-type InAs nanowires can be obtained.