Controllable p–n Switching Behaviors of GaAs Nanowires via an Interface Effect

Abstract

Due to the extraordinary large surface-to-volume ratio, surface effects on semiconductor nanowires have been extensively investigated in recent years for various technological applications. Here, we present a facile interface trapping approach to alter electronic transport properties of GaAs nanowires as a function of diameter utilizing the acceptor-like defect states located between the intrinsic nanowire and its amorphous native oxide shell. Using a nanowire field-effect transistor (FET) device structure, p- to n-channel switching behaviors have been achieved with increasing NW diameters. Interestingly, this oxide interface is shown to induce a space-charge layer penetrating deep into the thin nanowire to deplete all electrons, leading to inversion and thus p-type conduction as compared to the thick and intrinsically n-type GaAs NWs. More generally, all of these might also be applicable to other nanowire material systems with similar interface trapping effects; therefore, careful device design considerations are required for achieving the optimal nanowire device performances.

Surfactant-assisted chemical vapour deposition of high-performance small-diameter GaSb nanowires

“…All of these results are analogous to the case of sulfur surfactant growth of GaSb NWs, in which sulfur is employed as the surfactant with the function of stabilizing the surface group V atoms, inhibiting the uncontrolled NW radial growth to give thin and uniform NWs. Notably, these small diameter GaAs NWs also demonstrate the p-type semiconductor behaviour, consistent with previous reports 33 . In the literature, it is shown that GaAs NWs would yield different electronic behaviours with different NW diameters, in which thin GaAs NWs would give p-type conduction while thick NWs would give n-type conduction, owing to the interface trapping states existed between the intrinsic GaAs core and its amorphous oxide shell.…”

“…2a) explicitly shows the lattice of the spherical catalytic seed as well as the body, inferring a vapour-liquid-solid (VLS) or vapour-solid-solid growth mode. In addition, there is an amorphous layer of B2 nm around the NW body, which is always observed in the literature 33,34 . On the basis of the highresolution transmission electron microscope imaging and corresponding reciprocal lattice spots extracted by fast Fourier transform, the NW has a catalyst/NW interface orientation relationship of cubic AuGa 2 {111}|cubic GaSb{111}, without any noticeable amount of crystal defects such as stacking faults or inversion domains, and so on.…”

“…In the literature, it is shown that GaAs NWs would yield different electronic behaviours with different NW diameters, in which thin GaAs NWs would give p-type conduction while thick NWs would give n-type conduction, owing to the interface trapping states existed between the intrinsic GaAs core and its amorphous oxide shell. As a result, because of the sulfur passivation on the NW surface here, the surface oxide formation and its corresponding interface trapping effect are significantly reduced and a lower ON current (less p-type) results, as compared with the GaAs NWs prepared by conventional solid-source CVD method 33 . In summary, the adopted surfactant-assisted CVD approach can also be successfully implemented for the growth of GaAs NWs, further illustrating this surfactant-assisted scheme as a versatile growth platform extending to other NW material systems.…”

Strong Schottky barrier reduction at Au-catalyst/GaAs-nanowire interfaces by electric dipole formation and Fermi-level unpinning

“…This value is in good agreement with the experimental value of 30 A V À 1 cm À 2 deduced from our STM measurements. We therefore attribute the observed large ideality factor to surface depletion 23,25 due to NW surface oxidation 26,27 , an effect that we discussed above for NWs from series A. Mechanisms responsible for the low Schottky barrier. To elucidate the physics behind this surprisingly low Schottky barrier, we will discuss several mechanisms that could be responsible for this result.…”

“…In fact, to the best of our knowledge, this is the smallest Schottky barrier height ever reported for Au/GaAs interfaces. An important comment to this analysis is that the effective contact area A between the Au catalyst and GaAs NW most likely depends on the applied bias 23 V app owing to self-gating effects 24 in combination with a surface depletion 23,25 due to NW surface oxidation 26,27 . However, such effects will not affect the extracted barrier height, as evident from equation (1) as well as from the saturation of the barrier height observed in Fig.…”