The Need

The formation of dislocations in conventional thin film devices due to lattice mismatch strain restricts the choice of substrate and heterointerface. Nanowires can accommodate large strains due to their surface to volume ratio that permits large lattice mismatched heterostructures without dislocation formation and allows the formation of unconventional heterostructures, which are otherwise impossible in conventional planar films. However, nanowire devices are primarily grown on expensive single crystalline substrates. There is a need to develop nanowires and related materials on low-cost, scalable metal substrates.

The Technology

Researchers at The Ohio State University, led by Dr. Roberto Myers, have developed a method that utilizes molecular beam epitaxy (MBE) to deposit epitaxial semiconductor nanowire heterostructures directly on metal foil. The researchers demonstrated the growth of GaN nanowires and AlGaN/GaN heterostructures on Tantalum (Ta) metal foil, but the method could be applied to other families of semiconductors. To realize epitaxial GaN/AlGaN nanowire heterostructures on metal foil, the Ta metal foil is introduced to a vacuum chamber and heated to the growth temperature (~750 C for GaN/AlGaN). Ga and Al effusion cells as well as a N-plasma source were used as sources for Ga, Al, and N beam fluxes incident on the metal foil surface (standard MBE equipment). Nanowire heterostructures were formed by selecting the appropriate III/V flux ratio, substrate temperature, and shutter protocol to realize the desired composition variation. The nanowires grow in regular arrays along the metal foil surface. The nanowire light emiting diodes (LEDs) were processed into devices and tested revealing operational LEDs with a turn-on voltage of about 5 V and emission wavelength of about 350 nm. Wavelength modification may be done via changing the Al content percentage.

Commercial Applications

• Surface sanitation
• Water purification
• Nanomaterial Manufacturing
• Sensors

Benefits/Advantages

• Low cost and scalable method
• Nanowires grown on metal foils are of similar optical quality to those grown on single crystalline Si substrates
• The realization of operation nano LEDs grown directly on flexible metal foils provides a first step towards scalable roll-to-roll manufacturing of nanomaterial based solid-state optoelectronics