Field emission from GaN and (Al,Ga)N∕GaN nanorod heterostructures

Abstract

Vacuum field emission from GaN and (Al,Ga)N∕GaN nanorods with pyramidal tips has been measured. The turn-on fields, defined at a current density of 0.1μA∕cm2, were found to be 38.7 and 19.3V∕μm, for unintentionally doped GaN and (Al,Ga)N∕GaN nanorods, respectively. The 5nm (Al,Ga)N layer reduced the electron affinity at the surface, thereby lowering the turn-on field and increasing the current density. The nanostructures exhibit a field enhancement factor of approximately 65 and the work function of the (Al,Ga)N∕GaN nanorod heterostructure was estimated to be 2.1eV. The stability of the emission characteristics and the simple fabrication method suggest that intentionally doped and optimized (Al,Ga)N∕GaN nanorod heterostructures may prove suitable for field-emission device.

Ultralow Voltage GaN Vacuum Nanodiodes in Air

“…This comparison thus shows the enormous benefit of scaling vacuum electronic device gaps down to the nanoscale, allowing for an ∼2 orders of magnitude or greater reduction in turn-on voltage while enabling stable in-air or low-vacuum operation. Our nanogap devices also exhibit record low turn-on and very high currents compared to prior field-emission demonstrations of GaN structures including nanowire arrays and individual nanowires. − We note that the emitter sharpness of our devices is quite modest compared to prior work in the field utilizing emitters with near atomic sharpness, which should greatly improve manufacturability as well as emitter stability and durability.…”

“…This provides a scalable and high-yield path forward for manufacturable, monolithically integrated field-emission nanoelectronics, in contrast to prior impractical, one-off demonstrations such as focused-ion beam cutting and welding of 1D bottom-up grown nanowires and nanotubes . Future designs may benefit from using AlGaN instead of GaN because of its lower reported electron affinity, with prior field-emission measurements of GaN nanorod arrays showing a reduction in turn-on field by a factor of 2 when coated with a ∼ 5 nm layer of AlGaN . Field emission from a planar AlGaN/GaN 2D electron gas (2DEG) at nanoscale anode–cathode distances has also shown promise, and future architectures incorporating a 2DEG within the emitter tip could be intriguing.…”

“…37 Future designs may benefit from using AlGaN instead of GaN because of its lower reported electron affinity, with prior field-emission measurements of GaN nanorod arrays showing a reduction in turn-on field by a factor of 2 when coated with a ∼ 5 nm layer of AlGaN. 38 Field emission from a planar AlGaN/GaN 2D electron gas (2DEG) at nanoscale anode−cathode distances has also shown promise, 45 and future architectures incorporating a 2DEG within the emitter tip could be intriguing. Overall, these results show the attractive promise and inform the future design of a new class of scalable and robust, on-chip III-nitride based vacuum nanoelectronics operable at ultralow voltages and in air or relaxed vacuum requirements.…”

Crystallization Effects of Nanocrystalline GaN Films on Field Emission

“…The values of E on and data from other GaN nanostructured materials reported previously are summarized in Table . The E on of the microstructure modulated nanocrystalline GaN film (sample b) is smaller than that of the conventional film GaN materials − and even comparable to those of 1D GaN materials, ,− indicating efficient FE from the GaN films with the optimal microstructure. The detailed information about the F–N plot of GaN films is necessary to understand the microstructure effects on field electron emission.…”

Photonically excited electron emission from modified graphitic nanopetal arrays

“…Further investigation of the electronic structure, including detailed calculations of the energy bands could yield additional insight into the emission mechanism. However, this type of analysis is beyond the scope of this work, and the parabolic band assumption is often applied successfully to field emission from ultra-sharp emitter tips 41 including graphitic materials. 15 With these assumptions in place, the number of thermally emitted electrons with energy between E and E þ dE and velocity in the z-direction (i.e., normal to the surface) incident on the surface per unit time per unit area can be calculated as 30,42…”