M.A. Yildirim, K. Teker
Istanbul Sehir University,
Keywords: high temperature, GaN nanowires, nanowire FETs
Summary:Wide bandgap (WBG) semiconductor-based electronics are becoming the center of interest due to their ability to operate at high temperatures and high voltages. Gallium Nitride (GaN), as one of the WBG semiconductors, is a strong candidate that can meet expectations in high-temperature electronic applications such as military systems, automotive and aerospace control units, gas and oil exploration drilling systems. The superior physical properties of GaN nanowires such as high direct bandgap, high breakdown voltage, and high thermal conductivity, as well as high surface area to volume ratio, make it even more significant material for harsh environments. In this work, we investigate the electrical transport properties of a back-gated single GaN nanowire field-effect transistor (GaNNW-FET) at elevated temperatures. GaN nanowires produced at 1100°C in a hot-wall LPCVD reactor with Ga (99.999 % purity) and NH3 (% 99.99) materials as Ga and N sources, and H2 as the carrier gas. The single nanowire back-gated FET was built by the dielectrophoretic alignment method on a pair of pre-patterned electrodes (10nm Ti/90 nm Au) with a gap of 2.65 µm over a SiO2/Si substrate (highly-doped) via applying 10 Vpp voltage at 10 kHz frequency. Figures 1a and 1b show the grown GaN nanowires and an aligned-GaN nanowire between the two Au electrodes, respectively. To analyze transport properties (IDS-VDS and IDS-VGS), electrical measurements were performed at temperatures ranging from room temperature to as high as 350°C. Figure 2 shows IDS-VDS and IDS-VGS curves at temperatures ranging from room temperature to 350°C. The device performs very well until 250°C, whereas it shows some reduction in current values beyond 300°C. In fact, the drain current increases by 2.1, 13.6 and 19.7 times at the temperatures of 100°C and 200°C, 250°C, respectively, with respect to room temperature current at the same bias voltage of 1 V. The enhancement of current is likely due to the reduction of contact resistance between the nanowire and electrodes as well as an increase in thermally excited carrier concentration. On the other hand, degradation of current is likely due to the increase in lattice scattering, lowering the carrier mobility, of the GaN nanowire Moreover, the influence of high temperature on important transport properties such as transconductance, carrier concentration and carrier mobility will be presented in details. In summary, GaNNW-FET proves to be an excellent device capable of operating at high temperatures enabling the development of high-performance nanoelectronic devices especially for harsh conditions.