Growth and Characterization of GaN Nanostructures toward Electron Field Emitter Application

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We have investigated the growth of GaN nanostructures on three different Si substrates [Si(001) covered with native oxides, Si(001)(2 \times 1), and Si(111)(7 \times 7)] under N-rich conditions by using plasma-assisted molecular beam epitaxy (PA-MBE). For Si native oxides, hexagonal GaN (h-GaN) nanorods with a c-axis fiber texture are formed, i.e., the c-axis is aligned along the substrate normal without any preferential in-plane orientations. For the clean Si(001)(2 \times 1) substrates, c-axis-orientated nanorods are also grown with the epitaxial relationship of \langle 11\bar{2}0\rangle_{\text{h-GaN}}\parallel\langle 110\rangle_{\text{Si}} or \langle 12\bar{3}0\rangle_{\text{h-GaN}}\parallel\langle 110\rangle_{\text{Si}}. On the other hand, mesh-like structures of h-GaN are formed on the clean Si(111)(7 \times 7) substrates with the epitaxial relationship of \{0001\}_{\text{h-GaN}}\parallel\{111\}_{\text{Si}} and \langle 11\bar{2}0\rangle_{\text{h-GaN}}\parallel\langle 110\rangle_{\text{Si}}. The difference in the growth mode of GaN will be discussed in terms of the nitridation process during the initial stages of GaN growth, the chemical states of the substrate surfaces, and the substrate orientations. On the basis of the present findings, toward the fabrication of excellent electron field emitters by utilizing the GaN nanorods grown on the Si(001) with native oxides, we have shown the electron field-emission characteristics with a turn-on electric field as low as 1.25 V/μm at a current density of 0.1 μA/cm<sup>2</sup>and a field-emission current density as high as 2.5 mA/cm<sup>2</sup>at an applied electric field of 2.5 V/μm. We will demonstrate the fabrication of electron field emitter arrays of GaN nanorods on patterned W/SiO<inf>2</inf>/Si substrates in a selective-area growth mode by PA-MBE.
2013-11-25

Growth and Characterization of GaN Nanostructures toward Electron Field Emitter Application

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