Stable Low Resistance Ohmic Contacts To p-GaN

2001 ◽  
Vol 680 ◽  
Author(s):  
Mi-Ran Park ◽  
Wayne A. Anderson
Keyword(s):  
Contact Resistance ◽  
Photoelectron Spectroscopy ◽  
Ohmic Contacts ◽  
Depth Profiling ◽  
Force Microscopy ◽  
Low Resistance ◽  
Atomic Force ◽  
Current Voltage ◽  
Thermionic Field Emission ◽  
P Type

ABSTRACTStable and low-resistance Ohmic contacts are especially important for laser diodes where high current levels are required. Good contacts are especially difficult on p-type GaN which was the motivation for this study. The GaN was epitaxially grown on (0001) sapphire substrates by MOCVD. Resistivity of this layer was 3.5 Ohm-cm and thickness was 2 microns. After conventional cleaning followed by treatment in boiling HNO3: HCl (1:3), metallization was by thermally evaporating 40 nm Au / 60 nm Ni or 70 nm Au / 55 nm Pd. Heat treatment in O2 + N2 at various temperatures followed, with best results at 600 °C or 700 °C, respectively. Best values of the contact resistance were 1.8×10−4 Ohm-cm2 for Pd/Au and 2.65×10−4 Ohm-cm2 for Ni/Au contacts. After repetitive cycling from room temperature to 600 °C, the Ni contacts were very stable and more stable than the Pd contacts. X-ray photoelectron spectroscopy depth profiling showed the Ni contacts to be NiO followed by Au at the interface for the Ni/Au contacts whereas the Pd/Au contacts exhibited a Pd: Au solid solution. Some contacts were quenched in liquid nitrogen following sintering. These contacts were much more uniform under atomic force microscopy examination and gave a 3 times lower contact resistance with the Ni/Au design. Current-voltage-temperature analysis revealed that conduction was predominantly by thermionic field emission.

scholarly journals Optimization of Ohmic Contacts to p-GaAs Nanowires

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Marcelo Rizzo Piton ◽  
Teemu Hakkarainen ◽  
Joonas Hilska ◽  
Eero Koivusalo ◽  
Donald Lupo ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Grazing Incidence ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
Gaas Nanowires ◽  
Current Voltage ◽  
Metal Evaporation ◽  
Gaas Nanowire ◽  
P Type

AbstractThe performance of Ohmic contacts applied to semiconductor nanowires (NWs) is an important aspect for enabling their use in electronic or optoelectronic devices. Due to the small dimensions and specific surface orientation of NWs, the standard processing technology widely developed for planar heterostructures cannot be directly applied. Here, we report on the fabrication and optimization of Pt/Ti/Pt/Au Ohmic contacts for p-type GaAs nanowires grown by molecular beam epitaxy. The devices were characterized by current–voltage (IV) measurements. The linearity of the IV characteristics curves of individual nanowires was optimized by adjusting the layout of the contact metal layers, the surface treatment prior to metal evaporation, and post-processing thermal annealing. Our results reveal that the contact resistance is remarkably decreased when a Pt layer is deposited on the GaAs nanowire prior to the traditional Ti/Pt/Au multilayer layout used for p-type planar GaAs. These findings are explained by an improved quality of the metal-GaAs interface, which was evidenced by grazing incidence X-ray diffraction measurements in similar metallic thin films deposited on GaAs (110) substrates. In particular, we show that Ti exhibits low degree of crystallinity when deposited on GaAs (110) surface which directly affects the contact resistance of the NW devices. The deposition of a thin Pt layer on the NWs prior to Ti/Pt/Au results in a 95% decrease in the total electrical resistance of Be-doped GaAs NWs which is associated to the higher degree of crystallinity of Pt than Ti when deposited directly on GaAs (110).

High Quality Non-Alloyed Pt Ohmic Contacts to P-Type GaN Using Two-Step Surface Treatment

1999 ◽  
Vol 595 ◽  
Author(s):  
Ja-Soon Jang ◽  
Seong-Ju Park ◽  
Tae-Yeon Seong
Keyword(s):  
Surface Treatment ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Transport Mechanisms ◽  
High Quality ◽  
Ammonium Sulfide ◽  
Current Voltage ◽  
Specific Contact ◽  
Thermionic Field Emission ◽  
P Type

AbstractTwo-step surface-treatment is introduced to obtain low resistance Pt contacts to ptype GaN. The first step is performed after the mesa etching process using buffered oxide etch (BOE) and ammonium sulfide [(NH4)2Sx]. This is followed by the second step using BOE. The Pt contact, which was treated sequentially using ultrasonically boiled BOE (10 min) and boiled (NH4)2Sx (10 min), produces a specific contact resistance of 3.0 (±3.8)×10-5 Ωcm2. However, the contact, that was simply BOE-treated, yields 3.1 (±1.1)×10-2 Ωcm2. This indicates that the two-step surface treatment is promising technique for obtaining high quality ohmic contacts to p-GaN. Investigation of the electronic transport mechanisms using current-voltage-temperature (I-V-T) data indicates that thermionic field emission is dominant in the surface-treated Pt contacts.

I-V and Surface Topography Study of Nanostructure Porous Silicon Layer Prepared by Electrochemical Etching

2012 ◽  
Vol 576 ◽  
pp. 519-522 ◽  
Author(s):  
Fadzilah Suhaimi Husairi ◽  
Maslihan Ain Zubaidah ◽  
Shamsul Faez M. Yusop ◽  
Rusop Mahmood Mohamad ◽  
Saifolah Abdullah
Keyword(s):  
Electrical Properties ◽  
Porous Silicon ◽  
Surface Topography ◽  
Electrochemical Etching ◽  
Silicon Layer ◽  
Porous Silicon Layer ◽  
Force Microscopy ◽  
Atomic Force ◽  
Current Voltage ◽  
P Type

This article reports on the electrical properties of porous silicon nanostructures (PSiNs) in term of its surface topography. In this study, the PsiNs samples were prepared by using different current density during the electrochemical etching of p-type silicon wafer. PSiNs has been investigated its electrical properties and resistances for different surface topography of PSiNs via current-voltage (I-V) measurement system (Keithley 2400) while its physical structural properties was investigated by using atomic force microscopy (AFM-XE100).

Graphene growth on SiC and other substrates using carbon sources

2011 ◽  
Vol 1284 ◽  
Author(s):  
W. C. Mitchel ◽  
J. H. Park ◽  
Howard E. Smith ◽  
L. Grazulis ◽  
S. Mou ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Carbon Flux ◽  
Carbon Sources ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Graphene Films ◽  
Additional Control ◽  
P Type ◽  
Type Conduction

ABSTRACTDirect deposition of graphene from carbon sources on foreign substrates without the use of metal catalysts is shown to be an effective process with several advantages over other growth techniques. Carbon source molecular beam epitaxy (CMBE) in particular provides an additional control parameter in carbon flux and enables growth on substrates other than SiC, including oxidized Si and sapphire. CMBE using thermally evaporated C60 and a heated graphite filament on SiC is reported here. The graphene films were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and Hall effect. Graphene films on Si-face SiC grown using the C60 source have Bernal-like stacking and n-type conduction while those grown using the graphite filament have turbostratic stacking and p-type conduction. The sheet concentration for both n- and p-type doping is linearly dependent on film thickness.

scholarly journals Facile Synthesis of Highly Conductive Vanadium-Doped NiO Film for Transparent Conductive Oxide

2020 ◽  
Vol 10 (16) ◽  
pp. 5415
Author(s):  
Ashique Kotta ◽  
Hyung Kee Seo
Keyword(s):  
Electron Microscopy ◽  
Nickel Oxide ◽  
Photoelectron Spectroscopy ◽  
Transparent Conductive Oxide ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Conductive Oxide ◽  
P Type

Metal-oxide-based electrodes play a crucial role in various transparent conductive oxide (TCO) applications. Among the p-type materials, nickel oxide is a promising electrically conductive material due to its good stability, large bandgap, and deep valence band. Here, we display pristine and 3 at.%V-doped NiO synthesized by the solvothermal decomposition method. The properties of both the pristine and 3 at.%V:NiO nanoparticles were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), Raman spectroscopy, ultraviolet–visible spectroscopy (UV–vis), and X-ray photoelectron spectroscopy (XPS). The film properties were characterized by atomic force microscopy (AFM) and a source meter. Our results suggest that incorporation of vanadium into the NiO lattice significantly improves both electrical conductivity and hole extraction. Also, 3 at.%V:NiO exhibits a lower crystalline size when compared to pristine nickel oxide, which maintains the reduction of surface roughness. These results indicate that vanadium is an excellent dopant for NiO.

Low-Resistance Electrical Contacts to p-Type GaN by Using InxGa1-xN Cap Layers

2001 ◽  
Vol 693 ◽  
Author(s):  
Th. Gessmann ◽  
Y.-L. Li ◽  
J. W. Graff ◽  
E. F. Schubert ◽  
J. K. Sheu
Keyword(s):  
Contact Resistance ◽  
Electric Fields ◽  
Ohmic Contacts ◽  
Electrical Contacts ◽  
Specific Contact Resistance ◽  
Low Resistance ◽  
Transmission Line Method ◽  
Specific Contact ◽  
P Type ◽  
20 Nm

AbstractA novel type of low-resistance ohmic contacts is demonstrated utilizing polarization-induced electric fields in thin p-type InGaN layers on p-type GaN. An increase of the hole tunneling probability through the barrier and a concomitant significant decrease of the specific contact resistance can be attributed to a reduction of the tunneling barrier width in the InGaN capping layers due to the polarization-induced electric fields. The specific contact resistance of Ni (10 nm) / Au (30 nm) contacts deposited on the InGaN capping layers was determined by the transmission line method. Specific contact resistances of 1.2 × 10-2 Ω cm2 and 6 × 10-3 & cm2 were obtained for capping layer thicknesses of 20 nm and 2 nm, respectively.

scholarly journals Depth profiling X-ray photoelectron spectroscopy and atomic force microscopy of Cd(ii)- and Pb(ii)-selective electrodes based on nano metal sulfides

RSC Advances ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 3574-3581
Author(s):  
Abdulhakeem A. Ajadi ◽  
Nadia M. Shuaib ◽  
Adel F. Shoukry
Keyword(s):  
Atomic Force Microscopy ◽  
Photoelectron Spectroscopy ◽  
Depth Profiling ◽  
Metal Cations ◽  
Metal Sulfides ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Plastic Membrane

Nanoparticles of CdS and PbS as ionophres for plastic membrane metal cations electrodes.

Characterization of the Interface Between Metal Contacts and Epilayers of Doped Silicon Carbide

1995 ◽  
Vol 405 ◽  
Author(s):  
M. A. George ◽  
D. J. Larkin ◽  
J. Petit ◽  
A. Burger ◽  
S. H. Morgan ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Ohmic Contacts ◽  
Chemical Vapor ◽  
Metal Contacts ◽  
Aluminum Films ◽  
Force Microscopy ◽  
Atomic Force ◽  
Chemical Vapor Deposited ◽  
Before And After ◽  
P Type

AbstractAluminum contacts on chemical vapor deposited (CVD) SiC films were studied to examine variations in the chemical, morphological and electrical properties of the samples. Nitrogen and aluminum doped substrates were prepared to give n-type and p-type SiC epilayers respectively. These preparations were examined by surface sensitive spectroscopies and by atomic force microscopy (AFM). Samples were studied both before and after the deposition of aluminum films to compare differences between SiC(p++)/metal and SiC(n++)/metal contact interfacial properties. Aluminum has generally been found to have good adherence to the n+ epilayer but do not form good ohmic contacts, while metal films deposited on p+ epilayers have had poor adherence but have been found to provide better ohmic character. AFM images revealed nanometer sized clusters, attributed to excess Si on the n+ epilayers, while no clusters were observed on the p+ epilayers. XPS studies of the as-prepared samples indicated that the n+ epilayers had higher concentrations of oxides which may enhance adhesion. The chemical composition and morphology is discussed and correlated to the electrical properties obtained for the various samples.

scholarly journals High Quality Non-Alloyed Pt Ohmic Contacts to P-Type GaN Using Two-Step Surface Treatment

2000 ◽  
Vol 5 (S1) ◽  
pp. 521-527
Author(s):  
Ja-Soon Jang ◽  
Seong-Ju Park ◽  
Tae-Yeon Seong
Keyword(s):  
Surface Treatment ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Transport Mechanisms ◽  
High Quality ◽  
Ammonium Sulfide ◽  
Current Voltage ◽  
Specific Contact ◽  
Thermionic Field Emission ◽  
P Type

Two-step surface-treatment is introduced to obtain low resistance Pt contacts to p-type GaN. The first step is performed after the mesa etching process using buffered oxide etch (BOE) and ammonium sulfide [(NH4)2Sx]. This is followed by the second step using BOE. The Pt contact, which was treated sequentially using ultrasonically boiled BOE (10 min) and boiled (NH4)2Sx (10 min), produces a specific contact resistance of 3.0 (±3.8)×10−5 Ωcm2. However, the contact, that was simply BOE-treated, yields 3.1 (±1.1)×10−2 Ωcm2. This indicates that the two-step surface treatment is promising technique for obtaining high quality ohmic contacts to p-GaN. Investigation of the electronic transport mechanisms using current-voltage-temperature (I-V-T) data indicates that thermionic field emission is dominant in the surface-treated Pt contacts.

Comparative Analysis of the Nucleation and Growth of Copper on Different Low-k Polymers

2001 ◽  
Vol 714 ◽  
Author(s):  
V. Zaporojtchenko ◽  
J. Erichsen ◽  
T. Strunskus ◽  
K. Behnke ◽  
F. Faupel ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ion Beam ◽  
Depth Profiling ◽  
Nucleation And Growth ◽  
Force Microscopy ◽  
Teflon Af ◽  
Atomic Force ◽  
Transmission Electron ◽  
Beam Depth ◽  
Low K

ABSTRACTIn this work we present investigations of the nucleation and growth of evaporated copper on several low-k polymers. The evolving interfaces were characterized using transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results were compared between the PMDA/ODA polyimide, Teflon AF 1601 and Silk®. A diffusion coefficient for copper atoms in Silk® determined by low energy ion-beam depth profiling in conjunction with XPS is reported.

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