Comparison of wurtzite and zinc-blende GaAs surfaces as possible nanowire side walls: DFT stability calculations

For further clarification of the reasons for the occurrence of wurtzite type GaAs nanowires we investigate the energetic stability of a great variety of reconstruction patterns for the relevant wurtzite surfaces (0001)A, (0001)B, (1 (1) over bar 00), and (11 (2) over bar0) by the DFT supercell method for the first time. A procedure to obtain absolute surface energies of the polar WZ surfaces is presented. Surface energies in dependence on the chemical potential are compared with those of the related zinc-blende structures. For the side walls (1 (1) over bar 00)/(112) or (11 (2) over bar0)/(110), which play an important role for the stability of thin nanowires, the wurtzite structures are more stable than the related zinc-blende structures in a wide range of the chemical potential. From a comparison of the surface energies for WZ and ZB side walls it can be concluded that under strongly As-rich growth conditions only ZB type nanowires should be found and under less strongly As-rich conditions thin nanowires of the WZ type and thick nanowires of the ZB type should occur. (C) 2013 Elsevier B.V. All rights reserved.