Structural and electrical properties of GaAs/InSb core-shell nanowires

We present results about the growth, structural and strain relaxation properties and room temperature electrical transport of GaAs/InSb core-shell nanowires grown self-catalyzed by molecular beam epitaxy on Si (111) substrates. Due to the high lattice mismatch of about 14%, the growth of the shell proceeds from an island-based nucleation to a closed and rather smooth layer. High resolution transmission electron microscopy in combination with geometric phase analyses are used to identify different types of dislocations responsible for the strain relaxation on zinc blende and wurtzite core-shell nanowire segments. While on the wurtzite phase only Frank partial dislocations with b WZ,FP = c/2[0001] are found, the strain on the zinc blende phase is relaxed by perfect and Schokley and Frank partial dislocations with b ZB,p = a/2〈110〉, b ZB,SP = a/6〈112〉 and b ZB,FP = a/3〈111〉, respectively. Electrical transfer characteristics of the core-shell nanowires show an ambipolar behavior whose strength depends strongly on the dimensions of the nanowires.