Electrical transport properties of single GaN and InN nanowires

Abstract

The transport properties of single GaN and InN nanowires grown by thermal catalytic chemical vapor deposition were measured as a function of temperature, annealing condition (for GaN) and length/square of radius ratio (for InN). The as-grown GaN nanowires were insulating and exhibited n-type conductivity (n ; 2 3 10 17 cm ÿ3 , mobility of 30 cm 2 /V s) after annealing at 700°C. A simple fabrication process for GaN nanowire field-effect transistors on Si substrates was employed to measure the temperature dependence of resistance. The transport was dominated by tunneling in these annealed nanowires. InN nanowires showed resistivity on the order of 4 3 10 ÿ4 V cm and the specific contact resistivity for unalloyed Pd/Ti/Pt/Au ohmic contacts was near 1.09 3 10 ÿ7 V cm 2 . For In N nanowires with diameters ,100 nm, the total resistance did not increase linearly with length/square of radius ratio but decreased exponentially, presumably due to more pronounced surface effect. The temperature dependence of resistance showed a positive temperature coefficient and a functional form characteristic of metallic conduction in the InN nanowires.

Growth direction modulation and diameter-dependent mobility in InN nanowires

“…This was an interesting observation, based on which we assumed a unique radius-dependent mobility μ e (r ) for the NWs, which enabled us to extract mobility for many different diameters even from devices that contain multiple NWs (see the discussion below). Although dependence of NW conductance on diameter has been proposed earlier [23][24][25], to the best of our knowledge, dependence of mobility on NW diameter has not been proposed or investigated so far, mainly due to the difficulty in determining carrier mobility in InN NWs (through back-gate modulation of charges in an FET configuration) arising out of high carrier density [11,13].…”

“…An intriguing property of InN NWs observed in several past studies is the variation in conductance with NW diameter [23][24][25][26]. While some studies reported an increase in conductance with a decrease in NW diameter [23], and proposed theoretical models for the behavior [24], other studies found that the conductance can decrease with a decrease in NW diameter [25,26].…”

“…While some studies reported an increase in conductance with a decrease in NW diameter [23], and proposed theoretical models for the behavior [24], other studies found that the conductance can decrease with a decrease in NW diameter [25,26]. Clearly, the phenomenon of diameter-dependent transport in InN NWs needs to be examined more thoroughly, which can be highly significant for their applications in electronic, electromechanical and sensor devices.…”

Quantum transport in indium nitride nanowires

“…2,[4][5][6][7] Among the semiconductor nanowires, indium-based III-V semiconductors, such as InN, InAs and InSb, are known to have high conductivity and extremely high electron mobility. [8][9][10][11][12][13] Thus, it is of significant interest to investigate their quantum transport properties in order to evaluate them as the future building blocks for high-speed electronic devices. Figure 1c.…”

Surface Roughness Scattering of GaN Nanowire

“…3 shows the result of mobility limited by SRS versus electron density. The value of three dimensional electron density of GaN nanowire is usually in the range 10 17 -10 18 cm -3 [11]. Mobility goes up with electron density increasing, for the reason that higher electron density indicate stronger screen effect, which is same as GaN heterojunction [7].…”