High Temperature GaN and AlGaN Photovoltaic Detectors for UV Sensing Applications

MRS Proceedings ◽

10.1557/proc-482-1065 ◽

1997 ◽

Vol 482 ◽

Cited By ~ 1

Author(s):

J. M. Van Hove ◽

P. P. Chow ◽

R. Hickman ◽

J. J. Klaassen ◽

A. M. Wowchak ◽

...

Keyword(s):

Ohmic Contacts ◽

Elevated Temperatures ◽

Internal Quantum Efficiency ◽

Spectral Characteristics ◽

Bottom Layer ◽

Nitrogen Plasma ◽

Type Material ◽

Sensing Applications ◽

Photovoltaic Detectors ◽

P Type

AbstractAlGaN photodiode detectors are grown on (0001) sapphire by RF atomic nitrogen plasma molecular beam epitaxy. Both individual detectors and 1 × 10 element arrays are fabricated. The individual detectors have active areas of 0.5 mm2, 1.0 mm2, and 2.0 mm2. Individual elements in the l × 10 detector arrays range in size from 250×250 μm to 450×450 μm. The detectors are fabricated using a chlorine-based reactive ion etch (RIE) and refractory metal ohmic contacts. At room temperature, GaN p-i-n photovoltaic detectors show peak responsivity at 360 nm as high as 0.198 A/W, corresponding to an internal quantum efficiency of 85%. These detectors also exhibit five orders of magnitude of rejection for radiation longer than 500 nm. The electrical and spectral characteristics of these detectors are examined at elevated temperatures. The short wavelength UV responsivity remains fairly constant at elevated temperatures, while the peak responsivity actually increases with increasing temperature. The smooth surface morphology of heavily doped p-type material grown by MBE makes possible diode structures with a p-type bottom layer. The effect of the spectrally broader p-type material in the photodiode responsivity will be discussed.

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A Comparison of Single- and Multi-Layer Ohmic Contacts Based on Tantalum Carbide on n-Type and Osmium on p-Type Silicon Carbide at Elevated Temperatures

Materials Science Forum ◽

10.4028/www.scientific.net/msf.338-342.1001 ◽

2000 ◽

Vol 338-342 ◽

pp. 1001-1004 ◽

Cited By ~ 1

Author(s):

T. Jang ◽

G. Rutsch ◽

B. Odekirk ◽

L.M. Porter

Keyword(s):

Silicon Carbide ◽

Ohmic Contacts ◽

Elevated Temperatures ◽

Tantalum Carbide ◽

Type Silicon ◽

P Type

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Laser Direct Write and Gas Immersion Laser Doping Fabrication of SiC Diodes

MRS Proceedings ◽

10.1557/proc-815-j3.4 ◽

2004 ◽

Vol 815 ◽

Cited By ~ 2

Author(s):

Z. Tian ◽

N.R. Quick ◽

A. Kar

Keyword(s):

Ohmic Contacts ◽

Wafer Surface ◽

Direct Write ◽

Laser Doping ◽

Sensing Applications ◽

P Type ◽

Sic Wafer ◽

Laser Direct Write ◽

Defect Densities

AbstractLaboratory prototype SiC diodes are fabricated using a combination of gas immersion laser doping (GILD) and laser direct write (LDW) in situ metallization in a commercial SiC wafer. Trimethylaluminum (TMA) and nitrogen are the precursors used to produce p-type and n-type SiC, respectively. Using these techniques, a 150 nm p-type doped junction is fabricated in semiinsulating 6H-SiC and n-doped 4H-SiC wafers. Ohmic contacts are created by laser direct metallization producing carbon rich conductive phases in these doped materials. Alternatively an excimer laser can be used to create silicon rich Schottky contacts. The geometry of the diodes can be vertical or planar to the wafer surface and the laser processes are thought to reduce defect densities in the irradiated areas. These laser-processed diodes are intended for use in high temperature, high voltage and high frequency switching and sensing applications.

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Visible Blind uv GaN Photovoltaic Detector Arrays Grown by rf Atomic Nitrogen Plasma MBE

MRS Proceedings ◽

10.1557/proc-449-1227 ◽

1996 ◽

Vol 449 ◽

Cited By ~ 10

Author(s):

J.M. Van Hove ◽

P.P. Chow ◽

R. Hickman ◽

A.M. Wowchak ◽

J.J. Klaassen ◽

...

Keyword(s):

Ohmic Contacts ◽

Molecular Beam ◽

Contact Layer ◽

Nitrogen Plasma ◽

Atomic Nitrogen ◽

Detector Arrays ◽

Photovoltaic Detectors ◽

Silicon Doped ◽

Visible Blind ◽

Photovoltaic Detector

ABSTRACTRF atomic nitrogen plasma molecular beam epitaxy (MBE) was used to deposit gallium nitride (GaN) p-i-n junction photovoltaic detectors on (0001) sapphire. The detectors consisted of a bottom contact layer n-type silicon doped to 5 × 1018 cm−3. The intrinsic layer was undoped and possessed an n-type background carrier concentration of 1 × 1016 cm−3. The top /p-GaN layer was doped with magnesium to give a Hall concentration of 5 × 1017 cm−3. The p-type GaN cathodoluminescence (CL) spectra showed a strong 372 nm emission level in contrast to the 430 nm level observed in MOCVD samples. These layers were fabricated into 1 × 10 element detector arrays using a chlorine-based reactive ion etch (RIE) and refractory metal ohmic contacts. Peak responsivity of 0.11 AAV on detectors without anti-reflection coating were obtained at the GaN bandedge of 360 nm. The ultraviolet (UV) to visible rejection ratio was greater than 103 − 104 and was accredited to the reduction of the yellow defect levels in MBE material. Preliminary results on AlxGa1−xN detectors with responsivity peaks at 313 and 343 nm are presented as well.

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Low Resistance Ohmic Contact on p-type GaN Grown by Plasma-Assisted Molecular Beam Epitaxy

MRS Proceedings ◽

10.1557/proc-423-131 ◽

1996 ◽

Vol 423 ◽

Cited By ~ 3

Author(s):

Myung C. Yoo ◽

J. W. Lee ◽

J. M. Myoung ◽

K. H. Shim ◽

K. Kim

Keyword(s):

Molecular Beam Epitaxy ◽

Ohmic Contacts ◽

Doping Concentration ◽

Molecular Beam ◽

Plasma Source ◽

Nitrogen Plasma ◽

Specific Contact Resistance ◽

Metal Bilayers ◽

Auger Microscopy ◽

P Type

AbstractOhmic contacts on p-type GaN have been investigated. High quality GaN epilayers on cplane sapphire were prepared using plasma-assisted molecular beam epitaxy that utilized an inductively coupled rf nitrogen plasma source and solid source beams. The resulting film thickness and the doping concentration of the grown samples were in the range of 0.7–1.35 μm and 1018 – 1020/cm3, respectively. The metallization consisted of high work function metal bilayers which included a combinations of 25 nm-thick Ni, Ti, Pt and/or Cr and 200 nm-thick Au on the highly p-doped GaN in a transmission line model pattern. Ohmic contacts were formed by alloying the bi-layers using rapid thermal annealing (RTA) at temperatures in the range of 300–700 °C for 1 min under nitrogen ambient. Current-voltage measurements showed that the specific contact resistance was as low as 1.2 × 10 −4 Ω–cm2 for the sample having 1.4 × 1020/cm3p-type doping concentration with a Cr/Au contact annealed at 500 °C for 1 min by RTA. Judging from the scanning Auger microscopy results and the glancing angle x-ray diffraction analysis, this resistance is attributed to Cr diffusion into the GaN layer.

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Thermodynamics and Microstructure Development in the Thin Film Reaction of Aluminum on Silicon Carbide

MRS Proceedings ◽

10.1557/proc-403-489 ◽

1995 ◽

Vol 403 ◽

Cited By ~ 1

Author(s):

T. S. Hayes ◽

F. T. Ray ◽

K. P. Trumble ◽

E. P. Kvam

Keyword(s):

Thin Film ◽

Thin Films ◽

Silicon Carbide ◽

Ohmic Contacts ◽

Microstructure Development ◽

P Type ◽

Microstructural Studies

AbstractA refined thernodynamic analysis of the reaction between molen Al and SiC is presented. The calculations indicate much higher Si concentrations for saturation with respect to AkC 3 formation than previously reported. Preliminary microstructural studies confirm the formation of interfacial A14C3 for pure Al thin films on SiC reacted at 9000C. The implications of the calculations and experimental observations for the production of ohmic contacts to p-type SiC are discussed.

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Correlation between the electrical properties and the interfacial microstructures of TiAl-based ohmic contacts to p-type 4H-SiC

Journal of Electronic Materials ◽

10.1007/s11664-004-0203-x ◽

2004 ◽

Vol 33 (5) ◽

pp. 460-466 ◽

Cited By ~ 50

Author(s):

S. Tsukimoto ◽

K. Nitta ◽

T. Sakai ◽

M. Moriyama ◽

Masanori Murakami

Keyword(s):

Electrical Properties ◽

Ohmic Contacts ◽

P Type

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Improvement of the Specific Contact Resistance on P-Type 4H-SiC by Using a Highly P-Typed Doped 4H-SiC Layer Selectively Grown by VLS Transport

Materials Science Forum ◽

10.4028/www.scientific.net/msf.806.57 ◽

2014 ◽

Vol 806 ◽

pp. 57-60

Author(s):

Nicolas Thierry-Jebali ◽

Arthur Vo-Ha ◽

Davy Carole ◽

Mihai Lazar ◽

Gabriel Ferro ◽

...

Keyword(s):

Contact Resistance ◽

Ohmic Contacts ◽

Schottky Barrier Height ◽

Annealing Temperature ◽

Process Condition ◽

Specific Contact Resistance ◽

High Doping Level ◽

Annealing Temperatures ◽

Specific Contact ◽

P Type

This work reports on the improvement of ohmic contacts made on heavily p-type doped 4H-SiC epitaxial layer selectively grown by Vapor-Liquid-Solid (VLS) transport. Even before any annealing process, the contact is ohmic. This behavior can be explained by the high doping level of the VLS layer (Al concentration > 1020 cm-3) as characterized by SIMS profiling. Upon variation of annealing temperatures, a minimum value of the Specific Contact Resistance (SCR) down to 1.3x10-6 Ω.cm2 has been obtained for both 500 °C and 800 °C annealing temperature. However, a large variation of the SCR was observed for a same process condition. This variation is mainly attributed to a variation of the Schottky Barrier Height.

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Selective Area Deposition of Passivants, Insulators, and Epitaxial Films of II-VI Compound Semiconductors

MRS Proceedings ◽

10.1557/proc-161-159 ◽

1989 ◽

Vol 161 ◽

Author(s):

D.L. Dreifus ◽

Y. Lansari ◽

J.W. Han ◽

S. Hwang ◽

J.W. Cook ◽

...

Keyword(s):

Ohmic Contacts ◽

Epitaxial Films ◽

Semiconductor Surface ◽

Epitaxial Layers ◽

Double Crystal ◽

Surface Areas ◽

Selective Area ◽

Lift Off ◽

P Type ◽

Area Deposition

ABSTRACTII-VI semiconductor surface passivants, insulators, and epitaxial films have been deposited onto selective surface areas by employing a new masking and lift-off technique. The II-VI layers were grown by either conventional or photoassisted molecular beam epitaxy (MBE). CdTe has been selectively deposited onto HgCdTe epitaxial layers as a surface passivant. Selective-area deposition of ZnS has been used in metal-insulator-semiconductor (MIS) structures. Low resistance ohmic contacts to p-type CdTe:As have also been realized through the use of selectively-placed thin films of the semi-metal HgTe followed by a thermal evaporation of In. Epitaxial layers of HgTe, HgCdTe, and HgTe-CdTe superlattices have also been grown in selective areas on CdZnTe substrates, exhibiting specular morphologies and double-crystal x-ray diffraction rocking curves (DCXD) with full widths at half maximum (FWHMs) as narrow as 140 arcseconds.

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