High-dielectric-constant Ta2O5/n-GaN metal-oxide-semiconductor structure

Abstract

High-dielectric-constant Ta2O5 has been grown on the n-GaN epifilm by rf magnetron sputtering. Photoluminescence measurement has been performed to compare the luminescence intensity with and without the dielectrics. Threefold increase in intensity is obtained, and a surface recombination velocity is estimated to be 3×104 cm/s as an upper limit using a modified dead-layer model. A metal-oxide-semiconductor structure has been fabricated with Al on n-GaN as the ohmic contact and on Ta2O5 as the gate metal. Capacitance-versus-voltage characteristics have been measured. The doping concentration obtained from the depletion regime is compared with the result of Hall measurement, which is 7.0×1016 cm−3. The flat-band voltage is obtained from the high-frequency data, and the effective oxide charge number density is calculated as 4.1×1012 cm−2. Indication of strong inversion appears at low reverse bias due to the high dielectric constant of Ta2O5, and matches closely with calculated values. Hysteresis is observed and ascribed to positive mobile charges derived as 2.1×1012 cm−2. The capacitance dependence on the frequency and the leakage current are discussed.

Electrical characterization of Au/n-GaN metal–semiconductor and Au/SiO2/n-GaN metal–insulator–semiconductor structures

“…Many researchers have explored various metal/insulator schemes for the fabrication of Schottky contacts on GaN [7][8][9][10][11][12][13]. Tu et al [7] fabricated GaN metal-oxide-semiconductor structure using the high-dielectric-constant Ta 2 O 5 and possible low threshold voltages were demonstrated with high-frequency C-V measurements.…”

“…Tu et al [7] fabricated GaN metal-oxide-semiconductor structure using the high-dielectric-constant Ta 2 O 5 and possible low threshold voltages were demonstrated with high-frequency C-V measurements. Chang et al [8] prepared silicon nitride (SiN)/GaN MIS diodes by electron cyclotron resonance chemical vapor deposition (ECR-CVD).…”

Investigations of GaN metal-oxide-semiconductor capacitors with sputtered HfO2 gate dielectrics

“…Many effective techniques are available for depositing insulators on GaN. They include plasma-enhanced chemical vapor deposition (PE-CVD), ebeam evaporation, low-pressure CVD, photo-CVD, sputtering and atomic layer deposition [10][11][12]14,15]. Among these techniques, sputtering offers the advantages of simplicity process, low cost and high throughput.…”

Properties of high k gate dielectric gadolinium oxide deposited on Si (1 0 0) by dual ion beam deposition (DIBD)

“…These requirements include dielectric constant, band gap, band alignment to silicon, low oxygen diffusivity, lower leakage current than SiO 2 at an equivalent oxide thickness (t eq defined as ðk SiO 2 =k oxide Þt phys ) less than 1.5 nm, thermodynamic stability in contact with silicon at temperature exceeding 800 C, high-quality interface with silicon with low interfacial state density [2]. Some binary metal oxides are currently under consideration as the potential replacements for SiO 2 as the gate dielectrics, such as Ta 2 O 5 [3,4], TiO 2 [5], ZrO 2 [6].…”