Transfer Printed Virtual Substrates
Photovoltaic cells (PV) containing group III elements (such as Aluminum, Gallium, and Indium) and group V elements (such as Nitrogen, Phosphorus, and Arsenic) are known as III-V semiconductors. Multi-junction PV cells made from III-V semiconductors offer greater efficiency than current silicon PV technologies and are well suited to concentrated PV (CPV) applications. However, the creation of III-V materials is an expensive process, needing multiple layers of growth that are precisely controlled and atomically smooth. Thus, a major barrier to the adoption of CPV technology using III-V semiconductors is that the cost per area is typically over 100 times more expensive than silicon. Approximately 50% of the cost in is due to the substrate needed to grow the layers so the crystal structure has high uniformity and low defect density. New processes to enable a practical and realistic re-use of a single substrate for the growth of multiple PV cells could decrease the cost of each PV cell.
Project Innovation + Advantages:
George Washington University (GWU) will develop a new technique to produce commercial III-V substrates called Transfer Printed Virtual Substrates (TPVS). To reduce costs, the team proposes using a single source substrate to grow numerous virtual substrate layers. The team will use an enabling technology, called micro-transfer printing (MTP), to transfer the layers from the source substrate, in the form of many microscale “chiplets,” and deposit them onto a low-cost handle (silicon, for example). Once printed, the clean surfaces of the MTP process allows each chiplet to complete the epitaxial growth process on the lower cost substrate after having been seeded from the initial source and having sacrificial layers in between to release the chiplets from the source wafer. The TPVS process can potentially yield tens to hundreds virtual substrates from a single source wafer. Any micro/nanoscale device grown on III-V substrates, such as sensors, detectors, lasers, power electronics, and high-speed transistors, will experience significant cost reductions as a direct result of TPVS deployment. TPVS can also reduce the demand for rare minerals used for a wide range of critical technological applications due to the greater efficiency with which each initial source substrate is utilized.