Flexible GaAs film for cheaper photovoltaics

Flexible GaAs film for cheaper photovoltaics

Technology News |
By Nick Flaherty

Researchers in the US have developed a flexible gallium arsenide (GaAs) film that could reduce the cost of photovoltaics, displays, wireless communication devices and medical devices.

Researchers at the University at Buffalo, Texas State University and TapeSolar have developed the large area flexible GaAs film using epitaxial deposition on a gallium substrate.

Molecular beam epitaxy (MBE) is used for the controlled growth of high quality GaAs layers on lattice matched Ge capped, flexible metal substrates that can be used with a roll to rool high volume manufacturing process..

“These single-crystal-like, gallium arsenide films could potentially be useful in numerous applications where large areas, flexibility, light weight and high performance are of interest,” said Amit Goyal, SUNY Distinguished Professor and SUNY Empire Innovation Professor at the University at Buffalo School of Engineering and Applied Sciences and founder of TapeSolar.

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In addition to being expensive, gallium arsenide substrates are only available in small sizes and are rigid. Alternative fabrication methods – such as epitaxial lift-off and direct wafer bonding – are promising but yet to be proven successful.

Instead of single crystal substrates, the researchers employed a single-crystal-like germanium substrate that is flexible and can be fabricated using roll-to-roll manufacturing. This process – similar to a printing press – is cost-effective and efficient.

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Researchers analyzed the new gallium arsenide semiconductor through X-ray diffraction, electron microscopy and photoluminescence spectrometry. Orientation image microscopy images show that across an entire 0.25 mm × 0.15 mm region containing multiple grains, the GaAs layer is essentially of the same orientation with only a few grain boundaries greater than a couple of degrees.

Cross-sectional TEM images show the top layer of GaAs is relatively defect-free and of good crystalline quality. The GaAs layer demonstrates high carrier-mobility and sharp photoluminescence peaks with intensity comparable to GaAs layers grown on rigid, single-crystal substrates. These hetroepitaxial GaAs layers on flexible, large-area, single-crystal-like substrates provide a potential route to fabrication of high-performance devices for optoelectronic applications.

Goyal leads the Laboratory for Heteroepitaxial Growth of Functional Materials and Devices. He founded TapeSolar in 2011. The work was performed by TapeSolar Inc. under a facilities use agreement at Texas State University.


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