GaN layers are grown on sapphire substrates with AlN buffer layers by the metalorganic chemical vapor deposition method. GaN layers are doped with Si. The electron density of the n-type GaN is 2×1017 cm−3. It is found that the GaN surface is etched with hydrogen (H2) plasma produced by supplying microwave power leading to the formation of the roughened surface of GaN. A variation in the surface morphology occurs due to microwave power and gas pressure. Field emission measurements are carried out for GaN with various surface morphologies. It is observed that the turn-on electric field decreases with increasing surface roughness of the GaN. A turn-on electric field of the electron emission is estimated to be as low as 12.4 V/μm.
n -type gallium nitride (GaN) layers grown on sapphire substrates by metalorganic chemical vapor deposition are used to examine field emission characteristics. The electron concentration of the GaN is 2×1017 cm−3. In order to enhance the electric field, the GaN surface is roughened by hydrogen (H2) plasma treatment. Boron nitride (BN) films are grown on the roughened surface of the GaN by plasma-assisted chemical vapor deposition. The turn-on electric field between the anode and sample surface is estimated to be 12.4 and 8.8 V/μm from the field emission characteristics of the roughened GaN and the BN/GaN samples, respectively. It is demonstrated that BN coating is effective in improving the field emission characteristics.
Articles you may be interested inEffect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system J. Appl. Phys. 115, 084308 (2014); 10.1063/1.4866995Low threshold field emission from high-quality cubic boron nitride films J. Appl. Phys. 111, 093728 (2012); 10.1063/1.4711093Effect of cubic phase evolution on field emission properties of boron nitride island films An individual multiwall carbon nanotube ͑CNT͒ synthesized without a catalyst by an arc discharge method is bonded to a tungsten tip. Field emission characteristics of the individual CNT coated with a boron nitride ͑BN͒ nanofilm are investigated. The BN film is synthesized by plasma-assisted chemical vapor deposition method in which boron trichloride ͑BCl 3 ͒ and nitrogen ͑N 2 ͒ are used as source gases. Deposition of the BN film with a thickness less than 10 nm onto the individual CNT is attempted. Field emission characteristics are measured in the chamber evacuated to 2 ϫ 10 −8 Pa. An anode electrode is set 25 mm away from the CNT sample. The turn-on electric field, designated as an electric field at an emission current of 1.0 nA, is compared between individual CNTs with and without the BN nanofilm. A significant reduction in the turn-on electric field is achieved by coating with the BN nanofilm. The turn-on electric field is estimated to be 1.2ϫ 10 −2 V / m for the uncoated individual CNT sample, and the turn-on electric field is estimated to be 8.2ϫ 10 −3 V / m for the CNT sample coated with BN nanofilm. Moreover, stable operation is demonstrated at an emission current as high as 1 ϫ 10 −5 A.
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