Research data supporting "Engineering the Photoresponse of InAs Nanowires"

Raw data from the figures in "Engineering the Photoresponse of InAs Nanowires". InAs nanowires were grown by metal–organic chemical vapor deposition (MOCVD). The growth conditions were chosen to grow wurtzite crystal structures with minimal stacking faults, minimal tapering, and hexagonal cross sections with {11̅00} side facets, as confirmed by transmission electron microscopy (TEM). The nanowire diameter was tightly controlled by selecting the diameter of the Au catalyst. Nanowire diameters, inclusive of surface oxide, of 30 ± 5 nm, 40 ± 5 nm, 65 ± 5 nm, and 110 ± 5 nm, respectively, were obtained, as confirmed by SEM. For TEM measurements, nanowires were mechanically transferred to a holey carbon grid. TEM was performed using a JEOL 2100F instrument operated at 200 keV. The nanowires were transferred to a doped Si wafer with 300 nm of thermally grown SiO2 which served as a global back gate. Contacts with a separation of 1 μm were patterned using e-beam lithography and sputter deposition of 70 nm Ni, followed by lift-off. To obtain low contact resistivity, prior to Ni deposition, the contact region of the nanowire was etched in 2% aqueous (NH4)2S solution at 40 °C for 10 min. Electrical measurements were carried out using a probe station connected to a Keithley 4200-SCS semiconductor characterization system. Illumination of the samples to measure the photoresponse was applied using a 3200 K halogen lamp with a power density of 30 mW cm–2. All measurements were carried out at room temperature under ambient conditions unless otherwise specified. For ALD passivation, after device fabrication, a 90 nm capping layer of Al2O3 was deposited using a Cambridge NanoTech ALD system at 120 °C using trimethylaluminum and H2O precursors. The probe pads were then exposed by etching through the Al2O3 with phosphoric acid