Abstract
Mg doping of GaAs nanowires has been established as a viable alternative to Be doping in order to achieve p-type electrical conductivity. Although reports on the optical properties are available, few reports exist about the physical properties of intermediate-to-high Mg doping in GaAs nanowires grown by molecular beam epitaxy (MBE) on GaAs(111)B and Si(111) substrates. In this work, we address this topic and present further understanding on the fundamental aspects. As the Mg doping was increased, structural and optical investigations revealed: i) a lower influence of the polytypic nature of the GaAs nanowires on their electronic structure; ii) a considerable reduction of the density of vertical nanowires, which is almost null for growth on Si(111); iii) the occurrence of a higher WZ phase fraction, in particular for growth on Si(111); iv) an increase of the activation energy to release the less bound carrier in the radiative state from nanowires grown on GaAs(111)B; and v) a higher influence of defects on the activation of nonradiative de-excitation channels in the case of nanowires only grown on Si(111). Back-gate field effect transistors were fabricated with individual nanowires and the p-type electrical conductivity was measured with free hole concentration ranging from 2.7 × 1016 cm−3 to 1.4 × 1017 cm−3. The estimated electrical mobility was in the range ≈0.3–39 cm2/Vs and the dominant scattering mechanism is ascribed to the WZ/ZB interfaces. Electrical and optical measurements showed a lower influence of the polytypic structure of the nanowires on their electronic structure. The involvement of Mg in one of the radiative transitions observed for growth on the Si(111) substrate is suggested.
Highlights
In recent years, semiconductor nanowires have attracted a great deal of interest as building blocks for a new generation of electronic and optoelectronic devices, namely, batteries, biological and chemical sensors, thermoelectric devices, laser diodes, photo detectors, integrated photonic circuits, and solar cells [1,2,3]
Electrical measurements performed on individual nanowire back-gate field effect transistors (FETs) allowed the estimation of the free hole concentration and the electrical mobility
scanning electron microscopy (SEM) images of tangled nanowires are presented in Figure 2: (a) and (b) show the border regions of bunches of nanowires in sample A and B, respectively, and (c) and (d) show equivalent images for inner regions
Summary
Semiconductor nanowires have attracted a great deal of interest as building blocks for a new generation of electronic and optoelectronic devices, namely, batteries, biological and chemical sensors, thermoelectric devices, laser diodes, photo detectors, integrated photonic circuits, and solar cells [1,2,3]. GaAs nanowires show a polytypic structure along the gowth axis that is characterized by the occurrence of a mixture of WZ and ZB phases [12,13,14] This fact creates an unintentional bandgap that critically influences the optical and electrical properties of the nanowires [11,12,13,14,15,16,17,18,19]. A few studies have focused on the optical and electrical properties of Mg-doped GaAs nanowires. It is very important to study the effect introduced by the substrate on the physical properties of Mg-doped GaAs nanowires. Electrical measurements performed on individual nanowire back-gate field effect transistors (FETs) allowed the estimation of the free hole concentration and the electrical mobility. A nominal free hole concentration of 3 × 1017 cm−3 was estimated by Hall effect measurements performed in a GaAs epilayer, grown on a non Au-coated substrate, simultaneously with the nanowire samples. The excitation power (P) was varied in the range ≈0.03–90 mW
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
