As vacancies, Ga antisites, and Au impurities in zinc blende and wurtzite GaAs nanowire segments from first principles

Abstract

In this paper some specific issues related to point defects in GaAs nanowires are addressed with the help of density functional theory calculations. These issues mainly arise from the growth of nanowires under conditions different from those used for thin films or bulk GaAs, such as the co-existence of zincblende and wurtzite polytypes, the use of gold particles as catalyst, and the arsenic-limited growth regime. Hence, we carry out density-functional calculations for As vacancies, GaAs antisites, and Au impurities in ZB and WZ GaAs crystals. Our results show that As vacancies can diffuse within in a ZB GaAs crystal with migration barriers of ∼1.9 eV. Within WZ GaAs, As vacancy diffusion is found to be anisotropic, with low barriers of 1.60 up to 1.79 eV (depending on doping conditions) in the ab-plane, while there are higher barriers of 2.07 to 2.44 eV to diffuse along the c-axis. The formation energy of Au impurities is found to be generally much lower than those of arsenic vacancies or GaAs antisites. Thus, Au impurities will be the dominant defects formed in Au-catalyzed nanowire growth. Moreover, we find that it is energetically more favorable by 1 to 2 eV for an Au impurity to replace a lattice Ga atom than a lattice As atom in GaAs. An Au substitutional defect for a lattice Ga atom in ZB GaAs is found to create a charge transfer level in the lower half of the band gap. While our calculations locate this level at Ev + 0.22 eV, taking into account the inaccuracy of the density functional that ought to be corrected by a downshift of Ev by about 0.2 eV results in good agreement with the experimental result of Ev + 0.4 eV.

High‐Responsivity Photodetection by a Self‐Catalyzed Phase‐Pure p‐GaAs Nanowire

“…In recent years, semiconductor nanowires (NWs) have received tremendous attention because of their enormous potential applications in nanoscale electronics and optoelectronics devices such as photodetectors (PDs), single electron transistors, single photon detectors, tunneling diodes, and nanolasers . Reduced dimensionality, large surface‐to‐volume ratio, and strong light–matter interaction make the NWs a solid candidate for optoelectronic applications .…”

Influence of vacancies on indium atom distribution in InGaAs and InGaN compounds

“…The last E f values are also in agreement with the above mentioned data. According to different papers [25,27,29,32,33] the values of the arsenic vacancy formation energy for GaAs are in the range (2.08-5.21) eV. The E f value for the arsenic vacancy in the In 0.5 Ga 0.5 As compound was theoretically evaluated as 2.52 [32] and 2.6 eV [27].…”

Direct detection of spontaneous polarization in wurtzite GaAs nanowires

“…It is well known that due to their catalytic growth mode III-V-semiconductor nanowires (NWs) can grow in crystal structures that differ from the stable bulk crystal structure-a circumstance that is often referred to as crystal structure polytypism. [1][2][3][4][5] This allows to study the properties of crystal phases which are not or only rarely accessible in bulk or 2D materials. In our case, this is gallium-arsenide (GaAs) in the wurtzite (WZ) phase, which has mostly been subject to theoretical works 6 so far, as there have been only very few publications about WZ in GaAs layers 7 or in bulk crystals after a special pressure treatment.…”