Requirements of Electrical Contacts to Photovoltaic Solar Cells

1990 ◽  
Vol 184 ◽  
Author(s):  
T. A. Gessert ◽  
T. J. Coutts
Keyword(s):  
Solar Cells ◽  
Contact Resistance ◽  
Large Scale ◽  
Electrical Contacts ◽  
Specific Contact Resistance ◽  
Specific Contact ◽  
Large Scale Integration ◽  
Adverse Environmental Conditions ◽  
Scale Integration ◽  
Photovoltaic Solar Cells

ABSTRACTThe importance of contacts to photovoltaic solar cells is often underrated mainly because the required values of specific contact resistance and metal resistivity are often thought to be relatively modest compared with those associated with very large scale integration (VLSI) applications. However, due to the adverse environmental conditions experienced by solar cells, and since many of the more efficient cells are economically advantageous only when operated under solar concentration, the requirements for solar cell contacts are sometimes more severe. For example, at one-sun operation, the upper limit in specific contact resistance is usually taken to be 10−2 Ω-cm2. However, at several hundred suns, this value should be reduced to less than 10−4 Ω-cm2. Additionally, since grid line fabrication often relies on economical plating processes, porosity and contamination issues can be expected to cause reliability and stability problems once the device is fabricated. It is shown that, in practice, these metal resistivity issues can be much more important than issues relating to specific contact resistance and that the problem is similar to that of providing stable, low resistance interconnects in VLSI. This paper is concerned with the design and fabrication of collector grids on the front of the solar cells and, although the discussion is fairly general, it will center on the particular material indium phosphide. This III-V material is currently of great importance for space application because of its resistance to the damaging radiation experienced in space.

Requirements of Electrical Contacts to Photovoltaic Solar Cells

1990 ◽  
Vol 181 ◽  
Author(s):  
T.A. Gessert ◽  
T.J. Coutts
Keyword(s):  
Solar Cells ◽  
Contact Resistance ◽  
Large Scale ◽  
Electrical Contacts ◽  
Specific Contact Resistance ◽  
Specific Contact ◽  
Large Scale Integration ◽  
Adverse Environmental Conditions ◽  
Scale Integration ◽  
Photovoltaic Solar Cells

ABSTRACTThe importance of contacts to photovoltaic solar cells is often underrated mainly because the required values of specific contact resistance and metal resistivity are often thought to be relatively modest compared with those associated with very large scale integration (VLSI) applications. However, due to the adverse environmental conditions experienced by solar cells, and since many of the more efficient cells are economically advantageous only when operated under solar concentration, the requirements for solar cell contacts are sometimes more severe. For example, at one-sun operation, the upper limit in specific contact resistance is usually taken to be 10−2 Ω-cm2. However, at several hundred suns, this value should be reduced to less than 10−4 Ω-cm2. Additionally, since grid line fabrication often relies on economical plating processes, porosity and contamination issues can be expected to cause reliability and stability problems once the device is fabricated. It is shown that, in practice, these metal resistivity issues can be much more important than issues relating to specific contact resistance and that the problem is similar to that of providing stable, low resistance interconnects in VLSI. This paper is concerned with the design and fabrication of collector grids on the front of the solar cells and, although the discussion is fairly general, it will center on the particular material indium phosphide. This III-V material is currently of great importance for space application because of its resistance to the damaging radiation experienced in space.

Contact Resistance and Methods for its Determination

1982 ◽  
Vol 18 ◽  
Author(s):  
S. Simon Cohen
Keyword(s):  
Integrated Circuits ◽  
Contact Resistance ◽  
Large Scale ◽  
Ohmic Contacts ◽  
Vlsi Circuits ◽  
Single Element ◽  
Large Scale Integration ◽  
Proper Definition ◽  
Definition Of ◽  
Scale Integration

The problem of low resistance ohmic contacts to silicon has been of considerable technological interest. In recent years this problem has received special attention owing to the effect of scaling in very-large-scale integration (VLSI) technology. The field of ohmic contacts to semiconductors comprises two independent parts. First there exists the material science aspect. The choice of a suitable metallization system, the proper semiconductor parameters and the method of the contact formation is not obvious. Then there is the question of the proper definition of the contact resistance and the way it is measured.Several methods for contact resistance determination have been introduced in the past. All seem to have some drawbacks that either limit their usefulness or raise doubts as to their validity in certain situations. We shall discuss the two-, three- and four-terminal resistor methods of measurement. Relevant theoretical considerations will also be included.For conventional integrated circuits with a moderate junction depth of 1–2 μm, aluminum is uniquely suited as a single-element metallization system. However, for VLSI applications it may become obsolete because of several well-defined metallurgical problems. Thus, other metallization systems have to be investigated. We shall briefly discuss some recent data on several other metallization systems. Finally, the problem of size effects on the contact resistance will be discussed. Recent experimental results suggest important clues regarding the development of alternative metallization systems for VLSI circuits and also point to revisions of estimates of achievable design rules.

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.

Specific Contact Resistance Measurements on Multilayer Interconnect Structures.

1983 ◽  
Vol 25 ◽  
Author(s):  
H.B. Harrison ◽  
G.K. Reeves
Keyword(s):  
Contact Resistance ◽  
Transmission Line ◽  
Single Crystal ◽  
Large Scale ◽  
Single Crystal Silicon ◽  
Vlsi Circuits ◽  
Specific Contact Resistance ◽  
Crystal Silicon ◽  
Specific Contact ◽  
Interfacial Contact Resistance

ABSTRACTAn integral part of very large scale integrated (VLSI) circuits is the multilayer structures for electrical interconnection and insulation. Many conducting materials are used for interconnection including polysilicon, silicon, silicides, polycides and metals. An important point in considering these materials is the interconnection between them and the corresponding characterization of the interface by way of the specific contact resistance, which directly affects the interfacial contact resistance.For a planar ohmic contact formed between a metal and any layer with a much larger sheet resistance (for example single crystal silicon) a technique based on the transmission line model provides a method of characterizing these contacts. However, for planar contacts between layers with comparable sheet resistivities for example polysilicon to single crystal silicon this technique must be modified. In this paper we review the transmission line approach used to obtain the specific contact resistance between such layers and provide initial results of measurements made on the poly to single crystal interface. We also present a series of test structures, currently under fabrication that will provide more detailed experimental data.

Plant hormones, plant growth regulators

2014 ◽  
Vol 155 (26) ◽  
pp. 1011-1018 ◽  
Author(s):  
György Végvári ◽  
Edina Vidéki
Keyword(s):  
Nervous System ◽  
Growth And Development ◽  
Large Scale ◽  
Essential Role ◽  
Higher Plants ◽  
Structure And Function ◽  
Wide Sense ◽  
Large Scale Integration ◽  
Scale Integration ◽  
And Function

Plants seem to be rather defenceless, they are unable to do motion, have no nervous system or immune system unlike animals. Besides this, plants do have hormones, though these substances are produced not in glands. In view of their complexity they lagged behind animals, however, plant organisms show large scale integration in their structure and function. In higher plants, such as in animals, the intercellular communication is fulfilled through chemical messengers. These specific compounds in plants are called phytohormones, or in a wide sense, bioregulators. Even a small quantity of these endogenous organic compounds are able to regulate the operation, growth and development of higher plants, and keep the connection between cells, tissues and synergy beween organs. Since they do not have nervous and immume systems, phytohormones play essential role in plants’ life. Orv. Hetil., 2014, 155(26), 1011–1018.

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