In situ off-axis electron holography of real-time dopant diffusion in GaAs nanowires

Abstract

Off-axis electron holography was used to reveal remote doping in GaAs nanowires occurring during in-situ annealing in a TEM. Dynamic changes to the electrostatic potential caused by carbon dopant diffusion upon annealing were measured across GaAs nanowires with radial p-p+ core-shell junctions. Electrostatic potential profiles were extracted from holographic phase maps and built-in potentials (Vbi) and depletion layer widths (DLWs) were estimated as function of temperature over 300-873 K. Simulations in absence of remote doping predict a significant increase of Vbi and DLWs with temperature. In contrast, we measured experimentally a nearly constant Vbi and a weak increase of DLWs. Moreover, we observed the appearance of a depression in the potential profile of the core upon annealing. We attribute these deviations from the predicted behavior to carbon diffusion from the shell to the core through the nanowire sidewalls, i.e. to remote doping, becoming significant at 673 K. The DLW in the p and p+ regions are in the 10-30 nm range.

Large Tolerance of Lasing Properties to Impurity Defects in GaAs(Sb)‐AlGaAs Core‐Shell Nanowire Lasers

“…[44] Dopant diffusion is also an issue in III-V NWs (for example GaAs NWs), as has been observed for a variety of dopant elements. [45][46][47] The pres-ence of point defects, either intrinsic or mediated by excess doping, can further aggravate dopant redistribution, and even lead to diffusion-induced layer disordering, seen in for example Sidoped AlGaAs/GaAs MQW structures. [48] Furthermore, point defects, such as vacancies, were found in large quantities in GaAsbased NWs, even without doping.…”