scholarly journals Performance Improvement of GaN Based Laser Diode Using Pd/Ni/Au Metallization Ohmic Contact

Coatings ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 291 ◽  
Author(s):  
Wenjie Wang ◽  
Wuze Xie ◽  
Zejia Deng ◽  
Haojun Yang ◽  
Mingle Liao ◽  
...  
Keyword(s):  
Laser Diode ◽  
Ohmic Contact ◽  
Threshold Current ◽  
Contact Resistivity ◽  
Excellent Thermal Stability ◽  
Barrier Heights ◽  
Ohmic Behavior ◽  
Surface Oxides ◽  
Specific Contact ◽  
Gan Film

We report an investigation of the effects of different metal systems and surface treatment on the contact performance of GaN lasers. We found that multi-element metal alloy and surface chemical treatment are the keys to achieve good ohmic behavior contacts on GaN laser diodes. Pd/Ni/Au contact demonstrates excellent thermal stability and lowest specific contact resistivity in these metal systems. Properly adjusting the thickness of the Pd and Ni layer and pretreating with the KOH solution can further improve the ohmic contact performance. The improved ohmic behavior of the KOH solution pretreated Pd/Ni/Au contact is attributed to removing surface oxides and the reduction of the schottky barrier heights due to the metal Pd has a high work function and the interfacial reactions occurring between the Pd, Ni, Au, and GaN extends into the GaN film. As a result, a low contact resistivity of 1.66 × 10−5 Ω·cm2 can be achieved from Pd(10 nm)/Ni(10 nm)/Au(30 nm) contacts with KOH solution pretreated on top of the laser diode structure. The power of the GaN based laser diode with the Pd/Ni/Au metallization ohmic contact can be enhanced by 1.95 times and the threshold current decreased by 37% compared to that of the conventional ohmic contact Ni/Au.

Optimization of Ni/Nb Ratio for High-Temperature-Reliable Ni/Nb Silicide Ohmic Contact on 4H-SiC

2019 ◽  
Vol 963 ◽  
pp. 498-501
Author(s):  
Vuong Van Cuong ◽  
Seiji Ishikawa ◽  
Hiroshi Sezaki ◽  
Tomonori Maeda ◽  
Satoshi Yasuno ◽  
...  
Keyword(s):  
High Temperature ◽  
Ohmic Contact ◽  
Contact Resistivity ◽  
Specific Contact Resistance ◽  
X Ray Diffraction ◽  
High Concentration ◽  
Transfer Length ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
Specific Contact Resistivity

Low specific contact resistivity and high-temperature reliability of the Ni (x)/Nb (100-x) (where x = 25, 50, 75 nm) ohmic contact to 4H-SiC were investigated. After the annealing process at 1000°C for 3 min in N2 ambient, the I-V curves indicated that all the contacts exhibited the ohmic behaviors. Based on the transfer length method, the specific contact resistivity of the contacts were extracted. High concentration of Ni was responsible for low specific contact resistance of the Ni (75)/Nb (25)/4H-SiC sample by the formation of Ni2Si compound after the fabrication process. However, this contact lost the ohmic behavior at low temperature of 150°C. Whereas, both Ni (50)/Nb (50)/4H-SiC and Ni (25)/Nb (75)/4H-SiC contacts remained the ohmic behavior for 100-hour aging at 400°C. Two-dimensional X-ray diffraction analyses showed that the presence of carbon agglomeration formed at the interface of the Ni (75)/Nb (25)/4H-SiC contact caused the degradation of this sample when being aged at high temperature environment. Meanwhile, higher concentration of Nb in the Ni (50)/Nb (50)/4H-SiC and Ni (25)/Nb (75)/4H-SiC samples improved the ability to collect the excess carbon atoms and thus enhanced the high temperature reliability of these contacts when operating in high temperature ambient. Considering both low specific contact resistivity and high temperature reliability, the Ni (50)/Nb (50)/4H-SiC contact can be a good candidate for harsh environment applications.

Effect of Au distribution in NiO/Au film on the ohmic contact formation to p-type GaN

2005 ◽  
Vol 20 (2) ◽  
pp. 456-463 ◽  
Author(s):  
Jiin-Long Yang ◽  
J.S. Chen ◽  
S.J. Chang
Keyword(s):  
Electron Microscopy ◽  
Ohmic Contact ◽  
Incident Angle ◽  
Specific Contact Resistance ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Ohmic Behavior ◽  
Transmission Electron ◽  
Specific Contact ◽  
P Type

The distribution of Au and NiO in NiO/Au ohmic contact on p-type GaN was investigated in this work. Au (5 nm) films were deposited on p-GaN substrates by magnetron sputtering. Some of the Au films were preheated in N2 ambient to agglomerate into semi-connected structure (abbreviated by agg-Au); others were not preheated and remained the continuous (abbreviated by cont-Au). A NiO film (5 nm) was deposited on both types of samples, and all samples were subsequently annealed in N2 ambient at the temperatures ranging from 100 to 500 °C. The surface morphology, phases, and cross-sectional microstructure were investigated by scanning electron microscopy, glancing incident angle x-ray diffraction, and transmission electron microscopy. I-V measurement on the contacts indicates that only the 400 °C annealed NiO/cont-Au/p-GaN sample exhibits ohmic behavior and its specific contact resistance (ρc) is 8.93 × 10−3 Ω cm2. After annealing, Au and NiO contact to GaN individually in the NiO/agg-Au/p-GaN system while the Au and NiO layers become tangled in the NiO/cont-Au/p-GaN system. As a result, the highly tangled NiO-Au structure shall be the key to achieve the ohmic behavior for NiO/cont-Au/p-GaN system.

Ohmic Contact Formation to Doped GaN

1995 ◽  
Vol 395 ◽  
Author(s):  
L. L. Smith ◽  
M. D. Bremser ◽  
E. P. Carlson ◽  
T. W. Weeks ◽  
Y. Huang ◽  
...  
Keyword(s):  
Ohmic Contact ◽  
Electron Beam Evaporation ◽  
Integrated Analysis ◽  
Cross Sectional ◽  
Contact Materials ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
P Type ◽  
Ohmic Contact Formation ◽  
Contact Resistivities

ABSTRACTOhmic contact strategies for n- and p-type GaN have been investigated electrically, chemically, and microstructurally using transmission line measurements, high-resolution EELS and cross-sectional TEM, respectively. The contributions to contact performance from work function differences, carrier concentrations, annealing treatments, and interface metallurgy have been examined. The contact materials of Ti, TiN, Au, and Au/Mg were deposited via electron beam evaporation; Al was deposited via thermal evaporation. As-deposited Al and TiN contacts to highly doped n-GaN were ohmic, with room-temperature specific contact resistivities of 8.6×10−5 Ω cm2 and 2.5×10−5 Ωcm2 respectively. The Ti contacts developed low-resistivity ohmic behavior as a result of annealing; TiN contacts also improved with further heat treatment. For p-GaN, Au became ohmic with annealing, while Au/Mg contacts were ohmic in the as-deposited condition. The performance, structure, and composition of different contact schemes varied widely from system to system. An integrated analysis of the results of this study is presented below and coupled with a discussion of the most appropriate contact systems for both n- and p-type GaN.

Investigation of Cu-Ge/Gaas Metal-Semiconductor Interfaces for Low Resistance Ohmic Contacts

1996 ◽  
Vol 448 ◽  
Author(s):  
Serge Oktyabrsky ◽  
M.A. Borek ◽  
M.O. Aboelfotoh ◽  
J. Narayan
Keyword(s):  
Interfacial Layer ◽  
Ohmic Contacts ◽  
High Thermal Stability ◽  
Contact Resistivity ◽  
Polycrystalline Layer ◽  
Ohmic Behavior ◽  
Semiconductor Interfaces ◽  
Transmission Electron ◽  
Specific Contact ◽  
Specific Contact Resistivity

AbstractChemistry and interfacial reactions of the Cu-Ge alloyed ohmic contacts to n-GaAs with extremely low specific contact resistivity (6.5×10-7 Ω·cm2 for n~1017 cm-3) have been investigated by transmission electron microscopy, EDX and SIMS. Unique properties of the contact layers are related to the formation (at Ge concentration above 15 at.%) of a polycrystalline layer of ordered orthorhombic ε1-Cu3Ge phase. Formation of the ε1-phase is believed to be responsible for high thermal stability, interface sharpness and uniform chemical composition. The results suggest that the formation of the ζ- and ε1,-Cu3Ge phases creates a highly Ge-doped n+-GaAs interfacial layer which provides the low contact resistivity. Layers with Ge deficiency to form ζ-phase show nonuniform intermediate layer of hexagonal β-Cu3As phase which grows epitaxially on Ga{111} planes of GaAs. In this case, released Ga diffuses out and dissolves in the alloyed layer stabilizing the ζ-phase which is formed in the structures with average Ge concentration of as low as 5 at.%. These layers also exhibit ohmic behavior.

Microstructure, electrical properties, and thermal stability of Au-based ohmic contacts to p-GaN

1997 ◽  
Vol 12 (9) ◽  
pp. 2249-2254 ◽  
Author(s):  
L. L. Smith ◽  
R. F. Davis ◽  
M. J. Kim ◽  
R. W. Carpenter ◽  
Y. Huang
Keyword(s):  
High Temperature ◽  
Ohmic Contacts ◽  
Microstructural Characterization ◽  
Secondary Phase ◽  
High Resolution Electron Microscopy ◽  
Contact Resistivity ◽  
Cross Sectional ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
Specific Contact Resistivity

The work described in this paper is part of a systematic study of ohmic contact strategies for GaN-based semiconductors. Gold contacts exhibited ohmic behavior on p-GaN when annealed at high temperature. The specific contact resistivity (ρc) calculated from TLM measurements on Au/p-GaN contacts was 53 Ω · cm2 after annealing at 800 °C. Multilayer Au/Mg/Au/p-GaN contacts exhibited linear, ohmic current-voltage (I-V) behavior in the as-deposited condition with ρc = 214 Ω · cm2. The specific contact resistivity of the multilayer contact increased significantly after rapid thermal annealing (RTA) through 725 °C. Cross-sectional microstructural characterization of the Au/p-GaN contact system via high-resolution electron microscopy (HREM) revealed that interfacial secondary phase formation occurred during high-temperature treatments, which coincided with the improvement of contact performance. In the as-deposited multilayer Au/Mg/Au/p-GaN contact, the initial 32 nm Au layer was found to be continuous. However, Mg metal was found in direct contact with the GaN in many places in the sample after annealing at 725 °C for 15 s. The resultant increase in contact resistance is believed to be due to the barrier effect increased by the presence of the low work function Mg metal.

An investigation of a nonspiking Ohmic contact to n-GaAs using the Si/Pd system

1988 ◽  
Vol 3 (5) ◽  
pp. 922-930 ◽  
Author(s):  
L. C. Wang ◽  
B. Zhang ◽  
F. Fang ◽  
E. D. Marshall ◽  
S. S. Lau ◽  
...  
Keyword(s):  
Ohmic Contact ◽  
Rutherford Backscattering Spectrometry ◽  
Tunneling Current ◽  
Solid State Reactions ◽  
Cross Sectional ◽  
Ohmic Behavior ◽  
Transmission Electron ◽  
Specific Contact ◽  
Diffraction Patterns ◽  
Ohmic Contact Formation

A low-resistance nonspiking Ohmic contact to n-GaAs is formed via solid-state reactions utilizing the Si/Pd/GaAs system. Samples with Si to Pd atomic ratios greater than 0.65 result in specific contact resistivity of the order of 10−6 Ω cm2, whereas samples with atomic ratios less than 0.65 yield higher specific contact resistivities or rectifying contacts. Rutherford backscattering spectrometry, cross-sectional transmission electron microscopy, and electron diffraction patterns show that a Pd, Si layer is in contact with GaAs with excess Si on the surface after the Ohmic formation annealing. This observation contrasts with that on a previously studied Ge/Pd/GaAs contact where Ohmic behavior is detected after transport of Ge through PdGe to the interface with GaAs. Comparing the Ge/Pd/GaAs system with the present Si/Pd/GaAs system suggests that a low barrier heterojunction between Ge and GaAs is not the primary reason for Ohmic contact behavior. Low-temperature measurements suggest that Ohmic behavior results from tunneling current transport mechanisms. A regrowth mechanism involving the formation of an n+ GaAs surface layer is proposed to explain the Ohmic contact formation.

Piezoresistive Sensitivity and Al Ohmic Contact of Highly Doped Polycrystalline Silicon Nano Thin Films

2011 ◽  
Vol 483 ◽  
pp. 789-793
Author(s):  
Chang Zhi Shi ◽  
Xiao Wei Liu ◽  
Xuan Wu ◽  
Hai Tao Zheng
Keyword(s):  
Thin Films ◽  
Ohmic Contact ◽  
Polycrystalline Silicon ◽  
Depletion Region ◽  
Contact Resistivity ◽  
Gauge Factor ◽  
Piezoresistive Effect ◽  
Specific Contact ◽  
Specific Contact Resistivity ◽  
Polycrystalline Silicon Films

The piezoresistive and ohmic contact properties of polycrystalline silicon nano thin films were investigated in this paper. The polycrystalline silicon films with different thicknesses and doping concentrations were deposited by LPCVD and doped with boron highly, and then the cantilever beam samples were fabricated by photolithography and wet etching. By measuring the gauge factor and specific contact resistivity, the specific contact resistivity of Al contacts can reach 2.4×10-3Ω·cm2 after the alloying at 450 °C for 20 min; the enhanced piezoresistive effect of highly doped polycrystalline silicon nano thin films was discovered. The conclusions indicated that the enhanced piezoresistive sensitivity of PNTFs is due to the modification of depletion region barrier by ultra high doping and film thickness thinning and the enhancement of tunneling piezoresistive effect. The distinct piezoresistive phenomenon of PNTFs could be utilized for the development and fabrication of miniature piezoresistive sensors.

scholarly journals Development of an Extreme High Temperature n-Type Ohmic Contact to Silicon Carbide

2012 ◽  
Vol 717-720 ◽  
pp. 841-844 ◽  
Author(s):  
Laura J. Evans ◽  
Robert S. Okojie ◽  
Dorothy Lukco
Keyword(s):  
Heat Treatment ◽  
Silicon Carbide ◽  
Ohmic Contact ◽  
Operating Temperature ◽  
Specific Contact Resistance ◽  
Transfer Length ◽  
Ohmic Behavior ◽  
Contact Metallization ◽  
Extreme High Temperature ◽  
Specific Contact

We report on the initial demonstration of a tungsten-nickel (75:25 at. %) ohmic contact to silicon carbide (SiC) that performed for up to fifteen hours of heat treatment in argon at 1000 °C. The transfer length method (TLM) test structure was used to evaluate the contacts. Samples showed consistent ohmic behavior with specific contact resistance values averaging 5 x 10-4 Ω-cm2. The development of this contact metallization should allow silicon carbide devices to operate more reliably at the present maximum operating temperature of 600 °C while potentially extending operations to 1000 °C.

Electrical and microstructural characteristics of Ge/Cu ohmic contacts to n-type GaAs

1997 ◽  
Vol 12 (9) ◽  
pp. 2325-2331 ◽  
Author(s):  
M. O. Aboelfotoh ◽  
S. Oktyabrsky ◽  
J. Narayan ◽  
J. M. Woodall
Keyword(s):  
Ohmic Contacts ◽  
Field Effect Transistors ◽  
Contact Resistivity ◽  
Microstructural Characteristics ◽  
Cross Sectional ◽  
Ohmic Behavior ◽  
Transmission Electron ◽  
Wide Range ◽  
Specific Contact ◽  
Abrupt Interface

It is shown that Cu–Ge alloys prepared by depositing sequentially Cu and Ge layers onto GaAs substrates at room temperature followed by annealing at 400 °C form a low-resistance ohmic contact to n-type GaAs over a wide range of Ge concentration that extends from 15 to 40 at. %. The contacts exhibit a specific contact resistivity of 7 × 10−7 Ω cm2 on n-type GaAs with doping concentrations of 1 × 1017 cm−3. The contact resistivity is unaffected by varying the Ge concentration in the range studied and is not influenced by the deposition sequence of the Cu and Ge layers. Cross-sectional high-resolution transmission electron microscopy results show that the addition of Ge to Cu in this concentration range causes Cu to react only with Ge forming the ξ and ε1–Cu3Ge phases which correlate with the low contact resistivity. The ξ and ε1–Cu3Ge phases have a planar and structurally abrupt interface with the GaAs substrate without any interfacial transition layer. It is suggested that Ge is incorporated into the GaAs as an n-type impurity creating a highly doped n+-GaAs surface layer which is responsible for the ohmic behavior. n-channel GaAs metal-semiconductor field-effect transistors using ohmic contacts formed with the ξ and ε1–Cu3Ge phases demonstrate a higher transconductance compared to devices with AuGeNi contacts.

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