A technique for producing epitaxial films on reuseable substrates

Abstract

Using a new technique, which we have named the CLEFT process (cleavage of lateral epitaxial films for transfer), we have grown single-crystal GaAs films by vapor phase epitaxy (VPE) on reusable GaAs substrates. A carbonized photoresist mask with narrow, widely spaced stripe openings is first deposited on a (110) GaAs substrate. Epitaxial growth initiated within the openings, followed by lateral growth over the mask, produces a continuous single-crystal GaAs film. The upper surface of the film is bonded to a glass substrate, and the film is then cleaved from the GaAs substrate, leaving the surface of the latter in condition for repeating the procedure. The same GaAs substrate has been used for successive growth of four GaAs films, each about 4 cm2, ranging in thickness from 5 to 10 μm. The electrical properties of a CLEFT film were found comparable to those of conventional VPE layers. The CLEFT process should also be applicable to other semiconductors.

Photoelectrocatalysis: principles, nanoemitter applications and routes to bio-inspired systems

“…Optimization strategies include the preparation of nanoisland-type nanoemitter structures on an insulating, possibly lattice matched film, grown on top of the epilayer, the optimization of interface electronics and the use of non-noble metal nanoemitter materials that are capped by only a thin layer of noble metal catalysts. For technological applications, the use of thin films is mandatory and processes such as CLEFT (cleavage of epitaxial layers for transfer) 87,88 or PEEL (preferentially etched epitaxial liftoff) 89 should be considered. Fig.…”

Thin‐Film Silicon Solar Cells

“…The temporary support can be a Si wafer, which is reusable for growing other Si films. A liftoff CLEFT (cleavage of lateral epitaxial films for transfer) technique was originally developed for Ge-and GaAs-based cells using zone-melting recrystallization [29][30][31][32]. This technique is very successful, but is not warranted for a low-cost device.…”

Thin-Film III–V Solar Cells Using Epitaxial Lift-Off

“…the controlled spalling technology [61,62], are still in its infancy. In the last five years, companies like Alta Devices [63] and Microlink Devices [26,50,52,54] have developed a wafer-scale, epitaxial lift-off manufacturing process and are currently in pilot production. Activities in Europe are also initiated (tf2 devices).…”

“…The thin-film was not lifted off chemically like in ELO but mechanically using the CLEFT (Cleavage of Lateral Epitaxial Films for Transfer) technique [26]. The cell was used in a mechanical tandem in combination with CIS bottom cell.…”