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Effects of surface micromesas on reverse leakage current in InGaN/GaN Schottky barriers
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10.1063/1.4748317
/content/aip/journal/jap/112/4/10.1063/1.4748317
http://aip.metastore.ingenta.com/content/aip/journal/jap/112/4/10.1063/1.4748317

Figures

Image of FIG. 1.
FIG. 1.

(a) Schematic cross section of the InGaN/GaN Schottky diode and (b) the Nomarski optical microscopy top view of a real diode with surface micromesas.

Image of FIG. 2.
FIG. 2.

Nomarski optical microscopy images of (a) HP_InGaN/GaN, (b) LP_InGaN/GaN, (c) HP_GaN, and (d) LP_GaN. The inset in (b) is a zoom-in image of one surface micromesa.

Image of FIG. 3.
FIG. 3.

Representative SEM and AFM (tapping mode) micrographs of the surface micromesas. (a) A SEM micrograph; (b) an AFM micrograph; (c) 3-D AFM micrograph of (b); and (d) surface profile along the line shown in (b). (b)-(d) are from the same micromesa and (a) is from a different one. Numbers in (b) indicate the resolvable spiral steps.

Image of FIG. 4.
FIG. 4.

10 × 10 m2 AFM images of (a) HP_InGaN/GaN, (b) surface profile along the line in (a), (c) LP_InGaN/GaN, and (d) surface profile along the line in (c) after HPO etch.

Image of FIG. 5.
FIG. 5.

Surface micromesa mapping by Nomarski optical microscopy. (a) Surface micromesas before etch and (b) etch pits in the same area of a LP_InGaN/GaN sample. (c) A schematic superposition of image (a) and (b). The inset in (b) is a representative SEM image of a large etch pit shown in (b). The circles and dots in (c) represent the surface micromesas and nanopipe-related etch pits, respectively.

Image of FIG. 6.
FIG. 6.

An AFM (tapping mode) micrograph of surface micromesas with and without nanopipes at the center. The inset is a SEM image of a nanopipe without formation of a surface micromesa on the InGaN/GaN sample.

Image of FIG. 7.
FIG. 7.

Leakage current at a reverse bias of 30 V versus diode diameter for LP_InGaN/GaN and HP_InGaN/GaN Schottky diodes. The black dashed lines have slope of two and the color dashed curves represent the trend of measured data points.

Image of FIG. 8.
FIG. 8.

Leakage current at a reverse bias of 30 V versus micromesa number on the smallest (17-m diameter) LP_InGaN/GaN and HP_InGaN/GaN Schottky diodes.

Image of FIG. 9.
FIG. 9.

Representative forward IV curves for the smallest (17-m diameter) Ni-InGaN/GaN Schottky barriers (a) without surface micromesas and (b) with surface micromesas. The red dots are measured data and the solid black curves are calculated thermionic emission (TE) currents. In (b), the green and pink dashed curves represent the calculated TE currents for micromesas and InGaN/GaN, respectively. The black solid curve is the summation of the two dashed curves. The inset is the equivalent circuit diagram of the InGaN/GaN Schottky diodes with surface micromesas.

Image of FIG. 10.
FIG. 10.

Representative reverse-bias IV curves for the smallest (17-m diameter) Ni-InGaN/GaN Schottky barriers (a) without surface micromesas and (b) with surface micromesas. The red dots are measurement data and the solid curves are calculated tunneling currents. In (b), the green curve is calculated tunneling current for micromesas and the pink curve is calculated tunneling current for InGaN/GaN.

Image of FIG. 11.
FIG. 11.

RBS spectra of as-deposited, annealed at 200 °C for 60 min, 500 °C for 24 min, and 625 °C for 15 min Ni-InGaN/GaN samples. The inset on the left shows the zoom-in spectra and the inset on the right is a schematic diagram of the inter-diffusion at the Ni-InGaN interface.

Image of FIG. 12.
FIG. 12.

Leakage current at a reverse bias of 30 V versus diode diameter for LP_InGaN/GaN and HP_InGaN/GaN Schottky diodes before and after annealing at different temperatures.

Tables

Generic image for table
Table I.

Sample labels and key growth details used in this work (the coalescence time for HP buffer and LP buffer is ∼50 min and ∼10 min, respectively; the growth rate for HP buffer an LP buffer is ∼0.52 nm/s and ∼0.46 nm/s, respectively; and the InGaN growth rate is ∼0.0326 nm/s).

Generic image for table
Table II.

FWHM of symmetric (0002) and asymmetric (10 2) XRCs, surface micromesa density estimated under Nomarski optical microscopy and nanopipe and TD densities estimated by EPD in all samples.

Generic image for table
Table III.

Values of the key parameters used for all calculations in this work (the other parameters used in the calculations but not listed here are all theoretical physical constants, e.g., , , etc.).

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/content/aip/journal/jap/112/4/10.1063/1.4748317
2012-08-23
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Effects of surface micromesas on reverse leakage current in InGaN/GaN Schottky barriers
http://aip.metastore.ingenta.com/content/aip/journal/jap/112/4/10.1063/1.4748317
10.1063/1.4748317
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