Electrical Properties of Self-Assembled Branched InAs Nanowire Junctions Dmitry B. Suyatin, † Jie Sun, † Andreas Fuhrer, † Daniel Wallin, † Linus E. Fröberg, † Lisa S. Karlsson, ‡ Ivan Maximov, † L. Reine Wallenberg, ‡ Lars Samuelson, † and H. Q. Xu* ,† DiVision of Solid State Physics and The Nanometre Structure Consortium, Lund UniVersity, Box 118, S-221 00 Lund, Sweden, and Polymer & Materials Chemistry/ nCHREM, Lund UniVersity, Box 124, S-221 00 Lund, Sweden Received December 6, 2007; Revised Manuscript Received March 1, 2008 ABSTRACT We investigate electrical properties of self-assembled branched InAs nanowires. The branched nanowires are catalytically grown using chemical beam epitaxy, and three-terminal nanoelectronic devices are fabricated from the branched nanowires using electron-beam lithography. We demonstrate that, in difference from conventional macroscopic junctions, the fabricated self-assembled nanowire junction devices exhibit tunable nonlinear electrical characteristics and a signature of ballistic electron transport. As an example of applications, we demonstrate that the self-assembled three-terminal nanowire junctions can be used to implement the functions of frequency mixing, multiplication, and phase- difference detection of input electrical signals at room temperature. Our results suggest a wide range of potential applications of branched semiconductor nanostructures in nanoelectronics. Nanoelectronic elements made from self-assembled semi- conductor nanowires are considered nowadays as one of the most promising alternatives to conventional electronic ele- ments fabricated using lithography methods and tech- niques. 1–3 Recently, growth of branched nanowires has been demonstrated in different semiconductor material systems. 4–20 However, electrical properties of these self-assembled branched nanowires have rarely been studied. 11 Here we report on a study of the electrical properties of three-terminal junction devices made from self-assembled branched InAs nanowires. We show that the self-assembled nanoscale junctions exhibit tunable nonlinear electrical characteristics and a signature of ballistic electron transport. Thus, the branched nanowire junctions can provide a variety of applications in future nanoelectronics. As an example, we demonstrate in this work that the self-assembled three-terminal nanowire junctions can be used to implement the functions of frequency mixing, multiplication, and phase-difference detection in nanoelec- tronic circuits at room temperature. The branched self-assembled nanowires were catalytically grown using chemical beam epitaxy (CBE) in two steps. 21,22 The first step was the growth of vertical InAs nanowire trunks. For this step of growth, gold seed particles with diameters of about 70 nm were produced with an aerosol method 23 and deposited on an InAs (111) B substrate with a deposition density of 0.5 particles/μm 2 . The nanowire growth was carried out at 435 °C. Trimethylindium (TMIn) and tertiarybutylarsine (TBAs) were used as the growth sources. The source pressures in lines before the inlet valves during the growth were p As ) 200 Pa for TBAs and p In ) 15 Pa for TMIn. The lengths of the grown nanowire trunks were about 1.7 μm, and the diameters of the trunks, determined by the aerosol catalyst particle sizes, were found to be about 80 nm. After a second isotropic aerosol Au particle deposition, InAs nanowire branches were grown on the trunks. For this second growth step, aerosol particles with diameters of about 40 nm were deposited with a deposition density of 1 particle/ μm 2 on the substrates with the grown trunks. Nanowire branches were grown on the trunks for 25 min under a similar condition as for the growth of the trunks. The grown nanowire branches had a diameter of about 55 nm, and typically they grew faster at the base section of the trunks than on the top. Figure 1a shows a transmission electron microscope (TEM) image of some typical InAs nanowire junctions grown for this work. Figure 1b shows a high- resolution TEM image of the junction region of a branched nanowire. The image indicates that the grown branched InAs nanowire junctions had a wurtzite crystalline structure with some occasions of thin cubic sections or stacking faults. The nanowire trunks were grown in the [000–1] direction, while the branches were grown perpendicularly to the trunks in 〈1120〉 directions. After growth, branched nanowires were mechanically transferred onto the surface of a highly doped Si substrate * Corresponding author. E-mail: Hongqi.Xu@ftf.lth.se. † Solid State Physics. ‡ Polymer & Materials Chemistry/nCHREM. NANO LETTERS XXXX Vol. xx, No. x 000- 10.1021/nl073193y CCC: $40.75  XXXX American Chemical Society Published on Web 03/21/2008