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Even if silicon is the industry normal semiconductor in most electrical products, including the solar cells that photovoltaic panels utilize to convert sun rays into energy, it is hardly the most cost-efficient product on the market. For example, the semiconductor gallium arsenide and connected compound semiconductors provide practically 2 times the efficiency as silicon in solar devices, however they are rarely utilized in utility-scale applications because of their high production value.

U. of Illinois. professors J. Rogers and X. Li investigated lower-cost methods to produce thin films of gallium arsenide which also granted usefulness in the sorts of products they can be incorporated into.

If you can reduce significantly the expense of gallium arsenide and other compound semiconductors, then you might expand their variety of applications.

Usually, gallium arsenide is transferred in a individual thin layer on a smaller wafer. Either the ideal device is made specifically on the wafer, or the semiconductor-coated wafer is break up into chips of the preferred dimension. The Illinois group chose to put in multiple levels of the material on a individual wafer, making a layered, “pancake” stack of gallium arsenide thin films.

If you grow ten layers in 1 growth, you only have to fill the wafer 1 time. If you do this in 10 growths, loading and unloading with temp ramp-up as well as ramp-down get a lot of time. If you consider exactly what is necessary for every growth – the equipment, the research, the time, the workers – the overhead saving this approach gives is a considerable expense decrease.

Next the scientists separately peel off the layers and move them. To complete this, the stacks alternate levels of aluminum arsenide with the gallium arsenide. Bathing the stacks in a solution of acid and an oxidizing agent dissolves the layers of aluminum arsenide, freeing the single small sheets of gallium arsenide. A soft stamp-like device selects up the levels, 1 at a time from the top down, for move to another substrate – glass, plastic-type or silicon, depending on the application. Then the wafer could be reused for another growth.

By executing this it’s possible to produce considerably more material more quickly and more cost efficiently. This process could generate bulk amounts of material, as compared to just the thin single-layer method in which it is typically grown.

Freeing the material from the wafer also opens the opportunity of flexible, thin-film electronics produced with gallium arsenide or different high-speed semiconductors. To make products that could conform but still retain higher efficiency, which is significant.

In a paper released on-line May 20 in the academic journal Nature, the group explains its methods and shows 3 kinds of units making use of gallium arsenide chips produced in multilayer stacks: light products, high-speed transistors and solar cells. The authors also provide a comprehensive cost evaluation.

An additional advantage of the multilayer approach is the release from area constraints, especially essential for solar cells. As the levels are removed from the stack, they may be laid out side-by-side on one more substrate to make a significantly larger surface area, whereas the standard single-layer process restricts area to the dimension of the wafer.

For photovoltaics, you need large area coverage to catch as much sunshine as possible. In an extreme situation we might grow enough layers to have 10 times the area of the standard.

Up coming, the group programs to explore more prospective device applications and other semiconductor materials that could adapt to multilayer growth.

About the Article author – Shannon Combs publishes articles for the residential solar power cost blog, her personal hobby blog focused on tips to help home owners to save energy with sun power.

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