Nonalloyed Ohmic Contacts to N-Si Using a Strained Si0.5Ge0.5 Buffer Layer

1993 ◽  
Vol 320 ◽  
Author(s):  
Hsing-Kuen Liou ◽  
Edward S. Yang ◽  
K. N. Tu
Keyword(s):  
Buffer Layer ◽  
Photoelectron Spectroscopy ◽  
Ohmic Contacts ◽  
Depth Profiling ◽  
Binding Energies ◽  
Specific Contact Resistance ◽  
Strained Si ◽  
X Ray ◽  
Ohmic Behavior ◽  
Specific Contact

ABSTRACTNonalloyed shallow ohmic contacts to n-Si have been fabricated by using an 80 Å thick strained Si0.5Ge0.5 buffer layer grown by molecular beam epitaxy. X-ray photoelectron spectroscopy was employed to investigate the Si 2p and Ge 3d core level binding energies of the strained and the relaxed Si0.5Ge0.5 and to determine their relative Fermi level positions. It was found that the surfaces of strained Si0.5Ge0.5 exhibit pinning very close to the conduction band. Rutherford backscattering and Auger depth profiling were employed to determine the contact reactions using Ti, W or Pt as contact metals. In the case of Pt, a 500 Å W diffusion barrier can protect the ohmic behavior up to 550 °C for 30 min. The specific contact resistance of the Pt/W/Si0.5Ge0.5/n-Si contact extracted from the D-type cross-bridge Kelvin resistor was 3.5x10-5 Ω·cm2.

Investigation of Ge, As, and Au Diffusion in Non-Alloyed Epitaxial Au-Ge Ohmic Contacts to n-GaAs Using Secondary Ion Mass Spectroscopy Backside Sputter Depth-Profiling

1991 ◽  
Vol 240 ◽  
Author(s):  
H. S. LEE ◽  
R. T. Lareau ◽  
S. N. Schauer ◽  
R. P. Moerkirk ◽  
K. A. Jones ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Ion Beam ◽  
Depth Profiling ◽  
Depth Resolution ◽  
High Concentration ◽  
Ohmic Behavior ◽  
Preferential Sputtering ◽  
Specific Contact ◽  
Secondary Ion ◽  
Diffusion Profiles

ABSTRACTA SIMS backside sputter depth-profile technique using marker layers is employed to characterize the diffusion profiles of the Ge, As, and Au in the Au-Ge contacts after annealing at 320 C for various times. This technique overcomes difficulties such as ion beam mixing and preferential sputtering and results in high depth resolution measurements since diffusion profiles are measured from low to high concentration. Localized reactions in the form of islands were observed across the surface of the contact after annealing and were composed of Au, Ge, and As, as determined by SIMS imaging and Auger depth profiling. Backside SIMS profiles indicate both Ge and Au diffusion into the GaAs substrate in the isalnd regions. Ohmic behavior was obtained after a 3 hour anneal with a the lowest average specific contact resistivity found to be ∼ 7 × 100−6 Ω- cm2.

Current Transport Mechanisms in Au-Free Metallizations for CMOS Compatible GaN HEMT Technology

2020 ◽  
Vol 1004 ◽  
pp. 725-730
Author(s):  
Fabrizio Roccaforte ◽  
Monia Spera ◽  
Salvatore Di Franco ◽  
Raffaella Lo Nigro ◽  
Patrick Fiorenza ◽  
...  
Keyword(s):  
Barrier Height ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Current Transport ◽  
Large Area ◽  
Si Substrates ◽  
Ohmic Behavior ◽  
Specific Contact ◽  
Thermionic Field Emission

Gallium nitride (GaN) and its AlGaN/GaN heterostructures grown on large area Si substrates are promising systems to fabricate power devices inside the existing Si CMOS lines. For this purpose, however, Au-free metallizations are required to avoid cross contaminations. In this paper, the mechanisms of current transport in Au-free metallization on AlGaN/GaN heterostructures are studied, with a focus on non-recessed Ti/Al/Ti Ohmic contacts. In particular, an Ohmic behavior of Ti/Al/Ti stacks was observed after an annealing at moderate temperature (600°C). The values of the specific contact resistance ρc decreased from 1.6×104 Ω.cm2 to 7×105 Ω.cm2 with increasing the annealing time from 60 to 180s. The temperature dependence of ρc indicated that the current flow is ruled by a thermionic field emission (TFE) mechanism, with barrier height values of 0.58 eV and 0.52 eV, respectively. Finally, preliminary results on the forward and reverse bias characterization of Au-free tungsten carbide (WC) Schottky contacts are presented. This contact exhibited a barrier height value of 0.82 eV.

scholarly journals X-ray Photoelectron Spectroscopy (XPS) Depth Profiling for Evaluation of La2Zr2O7 Buffer Layer Capacity

Materials ◽  
2012 ◽  
Vol 5 (12) ◽  
pp. 364-376 ◽  
Author(s):  
Vyshnavi Narayanan ◽  
Klaartje de Buysser ◽  
Els Bruneel ◽  
Isabel van Driessche
Keyword(s):  
Buffer Layer ◽  
Photoelectron Spectroscopy ◽  
Depth Profiling ◽  
X Ray

scholarly journals Depth profiling of a CdS buffer layer on CuInS2 measured with X-ray photoelectron spectroscopy during removal by HCl etching

2012 ◽  
Vol 520 (7) ◽  
pp. 2829-2832 ◽  
Author(s):  
B. Johnson ◽  
J. Klaer ◽  
Ch.-H. Fischer ◽  
I. Lauermann
Keyword(s):  
Buffer Layer ◽  
Photoelectron Spectroscopy ◽  
Depth Profiling ◽  
X Ray

The Influence of Contact Composition, Pretreatment, and Annealing Gas on the Ohmic Behavior of Ti/Al-Based Ohmic Contacts to n-Al0.4Ga0.6N

2001 ◽  
Vol 680 ◽  
Author(s):  
K. O. Schweitz ◽  
T. G. Pribicko ◽  
S. E. Mohney ◽  
T. F. Isaacs-Smith ◽  
J. Williams ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Metal Layer ◽  
Active Role ◽  
Specific Contact Resistance ◽  
X Ray Diffraction ◽  
Group Iii ◽  
Ohmic Behavior ◽  
Annealing Conditions ◽  
Specific Contact ◽  
Group Iii Nitride

ABSTRACTAs the group III nitride semiconductor technology matures, an increasing number of devices are being fabricated with high Al fraction AlGaN. In this study, ohmic behavior is achieved using Ti/Al/Pt/Au contacts to n-Al0.4Ga0.6N, which is the highest Al fraction for which ohmic contact formation has been reported. The effect of contact composition, pretreatment, and annealing conditions is studied by 30 s isochronal annealing experiments between 500°C and 1000°C. A specific contact resistance ρC of (5±3) × 10−5 ωcm2 is obtained using Ti(26 nm)/Al(74 nm)/Pt(50 nm)/Au(50 nm) contacts to n-Al0.4Ga0.6N annealed in N2 at 800°C; however, this value is shown to be artificially high because the metal sheet resistance RM is 4 ω/⊏ causing an artifact in the data analysis. All contacts with ρC < 10−3 ωcm2 exhibit a local minimum in ρC after annealing at 800°C. The observed increase in ρC upon annealing at 850°C and 900°C, however, is not an artifact originating from a change in RM. The top Au layer is found to play an active role in forming ohmic contacts with low ρC, since omitting the Au layer yields an increase in ρC of two orders of magnitude after annealing at 800°C. Furthermore, leaving out the Au layer requires an annealing temperature of 700°C to result in linear I-V curves for currents up to 100 µA, as opposed to 500°C when the Au layer is present. The role of Au is further studied in Ti(26 nm)/Al(74 nm)/Ni(50 nm)/Au(50 nm) contacts, where Rutherford backscattering spectroscopy reveals Ga in the metal layer and/or Au buried deeper than the original semiconductor-metal interface, and x-ray diffraction indicates the formation of new phases to happen concurrently with a decrease in ρC of three orders of magnitude.

Engineering the Al-Ti/p-SiC Ohmic Contact for Improved Performance

2000 ◽  
Vol 640 ◽  
Author(s):  
J. Y. Lin ◽  
S. E. Mohney ◽  
M. Smalley ◽  
J. Crofton ◽  
J. R. Williams ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Ohmic Behavior ◽  
Contact Metallization ◽  
Specific Contact ◽  
Order Of Magnitude ◽  
Rich Liquid ◽  
Improved Performance ◽  
Definition Of

ABSTRACTThe influence of composition on Al-Ti ohmic contacts to 4H p-SiC was studied. When NA was 7 x 1018 cm−3, contacts with 70 wt.% or more Al became ohmic when annealed at 1000°C for 2 min, whereas when there was 60 wt.% or less Al, the contacts did not become ohmic even when annealed under more severe conditions (longer times and/or higher temperatures). Spiking of the contact metallization always accompanied ohmic behavior and could be correlated with Al-Ti compositions that contain both an Al-rich liquid and solid TiAl3 at 1000°C prior to reaction with SiC or evaporative loss of Al. For the 70 wt.× contacts, a specific contact resistance of 1.5 × 10−4 Ω cm2 was measured along with spiking of the metallization into the SiC with a room-mean-square interfacial roughness of 150 Å and a maximum spiking depth of 1200 Å. Although still a concern, this spiking was less severe than observed for the 90 wt.× composition. A conductive CrB2 cap layer was next demonstrated to retard evaporation of Al during annealing of the Al-Ti contacts with 70 wt.× Al. The cap allowed use of thinner contact layers, reducing the depth of spiking and improving the surface morphology and edge definition of the ohmic contacts, with a one order of magnitude penalty in the specific contact resistance.

The Effects of Ion Beam Mixing on Rapid Thermal Annealed Ohmic Contacts to N-GaAs

1990 ◽  
Vol 181 ◽  
Author(s):  
Seemi Kazmi ◽  
Roman V. Kruzelecky ◽  
David A. Thompson
Keyword(s):  
Surface Morphology ◽  
Contact Resistance ◽  
Thermal Annealing ◽  
Rapid Thermal Annealing ◽  
Ohmic Contacts ◽  
Ion Beam ◽  
Depth Profiling ◽  
Specific Contact Resistance ◽  
Ion Beam Mixing ◽  
Specific Contact

ABSTRACTNi/Ge/Au and Ni/Ge/Pd contacts have been made on 1018 cm-3 n-type GaAs. The contacts were subjected to ion beam mixing through the metallization using 70-130 keV Se+ ions and subsequently subjected to rapid thermal annealing (RTA). These are compared with unimplanted contacts produced by RTA techniques on the same substrate. The specific contact resistance ,pc, has been measured for the two systems. In addition, the contacts have been studied using Auger depth profiling and SEM studies have been used to determine surface morphology. Values of pc ∽ 10-6 -10-7 ohm-cm2 have been measured. It is observed that ion beam mixing or the addition of a Ti overlayer (to the Ni/Ge/Au) improves the contact morphology.

Fabrication and Characterization of Ohmic Contacts to 3C-SiC Layers Grown on Silicon

2019 ◽  
Vol 963 ◽  
pp. 485-489
Author(s):  
Monia Spera ◽  
Giuseppe Greco ◽  
Raffaella Lo Nigro ◽  
Salvatore di Franco ◽  
Domenico Corso ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Ohmic Contacts ◽  
Specific Contact Resistance ◽  
Silicon Substrates ◽  
X Ray Diffraction ◽  
X Ray ◽  
Specific Contact ◽  
Fabrication And Characterization ◽  
P Type

This paper reports on the formation and characterization of Ohmic contacts to n-type and p-type type 3C-SiC layers grown on silicon substrates. In particular, Ohmic contact behavior was obtained either using Ni or Ti/Al/Ni layers annealed at 950°C. The values of the specific contact resistance ρc estimated by means of circular TLM (C-TLM) structures varied in the range ~ 10-3-10-5 Ωcm2, depending on the doping level of the 3C-SiC layer. A structural analysis performed by X-Ray Diffraction (XRD) allowed to identify the main phases formed upon annealing, i.e., Ni2Si and Al3Ni2. The morphology of the reacted contacts depended on that of the underlying substrate. The results can be useful for the development of a variety of devices on the cubic 3C-SiC polytype.

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