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Pd Schottky barrier diodes were fabricated on undoped AlxIn0.02Ga0.98-xN/GaN with x less than 20%. The material properties, which were characterized by photoluminescence, x-ray diffraction, and atomic force microscopy, indicated that the quaternary samples were coherently grown on GaN template with high crystalline quality. The flatband barrier height obtained by capacitance-voltage (C-V) measurement increased with increasing Al mole fraction (increasing the band gap of the quaternary) up to 2.06 eV, in agreement with the predictions of the Schottky-Mott theory. However, current-voltage (I-V) measurements revealed that the barrier height decreased from 1.32 to 1.12 eV, which was accompanied by an increase in ideality factor from 1.04 to 1.73. The large difference of barrier height between I-V and C-V measurements could not be quantitatively explained by the traditional electron transport mechanisms of Schottky diode, such as tunneling effect, image force effect, and barrier inhomogeneity theory. Strong polarization effect in strained AlxIn0.02Ga0.98-xN/GaN heterostructure was proposed to account for the experimental results, since similar phenomena had been observed extensively in strained AlyGa1-yN/GaN heterojunction structures. [ABSTRACT FROM AUTHOR]

Discusses the fabrication of Schottky diodes of titanium, palladium and nickel/n-aluminum[sub0.11]gallium[sub0.89]nitride. Measurement of barrier heights; Experimental procedure; Use of metal lift-off technique for Schottky dots.

A Pd/InAlN Schottky diode with leakage current as low as \1.01 \times \10^-6\ \A/cm^2 at -5 V at 300 K has been fabricated. It is found that the current–voltage (I–V) characteristics of Pd/InAlN Schottky contact can be quantitatively described by taking into account the inhomogeneity of Schottky barrier height (SBH), and the SBH inhomogeneity is the main cause for the significant deviation from an ideal Schottky contact. The SBH inhomogeneity is suggested to be related to the quantum dotlike structure on InAlN surface, indicating the importance of surface effect to the investigations on those devices involving InAlN-based Schottky contact. [ABSTRACT FROM AUTHOR]

A series of InxAl1-xN-based Schottky solar-blind photodiodes are fabricated on the InxAl1-xN epilayers with high and very close crystal qualities. The quantum efficiency varies from 14.5% to 68.5%. The microstructure and strain state of epilayers are investigated in detail. It is found that the quantum efficiency of photodiode depends on the strain state in InxAl1-xN films. This indicates that adjusting the strain state in InxAl1-xN film is one of the promising approaches to optimize the performance of InAlN-based solar-blind photodiode. [ABSTRACT FROM AUTHOR]

The authors report the growth of InxAl1-xN with high crystal quality by metal organic chemical vapor deposition, the Pd/InxAl1-xN Schottky contacts with reverse current densities as low as 6.0×10-7 A/cm2 at -5 V and 2.1×10-5 A/cm2 at -10 V, and consequently significant improvement in the performance of InAlN-based Schottky solar-blind photodiodes with peak responsivity of 133 mA/W at 242 nm, corresponding to a quantum efficiency of 68.5%. The illumination is detectable under the intensity as weak as 10 nW/cm2. The rejection ratios by 300 nm are one order of magnitude for 10 nW/cm2 illumination and three orders of magnitude for 1 μW/cm2 illumination. [ABSTRACT FROM AUTHOR]

The authors report the high-performance AlGaN solar-blind Schottky photodiodes grown on AIN/sapphire templates by metal organic chemical vapor deposition. The devices exhibit dark current densities as low as 1.6×10-11 A/cm2 at -5 V bias. The peak responsivity is 41 mA/W at 256 nm in the photovoltaic mode, corresponding to a quantum efficiency of 20%. A sharp spectral response cutoff of more than two orders of magnitude by 300 nm is observed under a low illumination intensity of 10 nW/cm2. The zero-bias resistance-area product of the device is found to be 5.0×1012 Ω cm2, leading to an estimated detectivity of 7.0×1014 cm Hz1/2/W at 256 nm. [ABSTRACT FROM AUTHOR]

Solar-blind AlGaN Schottky photodiodes with a large active area of 2×2 mm have been fabricated on a AlN/sapphire template. The resulting devices show dark current density as low as 6.6×10-11 A at -5 V bias. A zero-bias peak responsivity of 38 mA/W was obtained at 260 nm, corresponding to an estimated detectivity of 1.2×1014 cm Hz1/2 W-1. [ABSTRACT FROM AUTHOR]

Pd/Ti/Au and Ni/Au Schottky barrier diodes (SBDs) were demonstrated on quaternary AlInGaN. Current–voltage properties indicated that near-ideal and high-performance SBDs had been realized with ideality factor of 1.05, 1.07 and barrier height of 1.32, 0.98 eV for Pd and Ni SBDs, respectively. Capacitance–voltage measurement revealed that the high-density two-dimensional electron gas (2DEG) located at the AlInGaN/GaN interface. Ruling out the possible contribution from piezoelectric polarization and conduction band offset, we believe that the formation of 2DEG is due to the existence of large spontaneous polarization in AlInGaN layer, which experimentally verifies the feasible application of quaternary AlInGaN in the high-electron-mobility transistor. [ABSTRACT FROM AUTHOR]

Ir/Ni/Ir metallisation was employed as Schottky contacts of GaN Schottky photodiodes. After annealing at 500°C in O[SUB2] for 1 min, the Schottky contact achieved the maximum barrier height of 1.28 eV and the minimum dark current densities of 1.8×10[SUB-10] A/cm[SUP2] at -5 V bias. The peak responsivity is 105 mA/W at zero bias and increases to 150 mA/W at -15 V bias. The detectivity was estimated as 5.8×10[SUP15] cmHz[SUP1/2] W[SUP-1] at zero bias. [ABSTRACT FROM AUTHOR]

GaN films were grown on sapphire and SiC substrates. The crystal qualities of GaN films were investigated by photoluminescence, atomic force microscopy, and electron-beam-induced current measurements, etc. It was found that the crystal quality of GaN on SiC is better than the one on sapphire. Ni/Au Schottky contacts were formed on the both samples. The electronic characteristics were obtained by current–voltage and capacitance–voltage measurements. Schottky diodes on sapphire substrate show breakdown voltage of -80 V. While for SiC substrate, the strong breakdown was not observed even at -100 V. The reverse leakage current of diodes based on SiC is over three orders of magnitude lower than that of sapphire substrate when the reverse voltage is above 50 V, which is due to the presence of low dislocation density and high thermal conductivity. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The realisation of a fully vertical gallium nitride (GaN)-on-silicon (Si) Schottky barrier diode (SBD) without using wafer bonding and Si substrate removal process is reported. The SBD presented a turn-on voltage of 0.69 V at 1 A/cm², breakdown voltage of 148 V with a specific on-resistance of 13.9 mO cm². The ideality factor and Schottky barrier height were 1.35 and 0.71 eV, respectively. An effective critical electric field was estimated to be 1.48 MV/cm. The Baliga's figure of merit for the SBD was calculated to be 1.57 MW/cm². These results indicate the great potential of GaNon- Si in achieving cost-effective fully vertical power device. [ABSTRACT FROM AUTHOR]

AlGaN/GaN-based planer Schottky barrier diodes (SBDs) with circular anode configuration were formed on AlN template and on sapphire. SBDs formed on AlN template exhibited clearly improved reverse-blocking characteristics compared with SBDs formed on sapphire. This appears to be due to their high crystal quality realised as a result of using AlN template. Breakdown voltages in those SBDs increased with the anode-to-cathode spacing and reached a high value of approximately 3 kV at a gap-spacing of 50 µm for SBDs formed on AlN template. [ABSTRACT FROM AUTHOR]