Laser liftoff of gallium arsenide thin films
- PDF / 376,646 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 1 Downloads / 186 Views
Research Letters
Laser liftoff of gallium arsenide thin films Garrett J. Hayes and Bruce M. Clemens, Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 Address all correspondence to Garrett J. Hayes at [email protected] (Received 13 October 2014; accepted 30 January 2015)
Abstract The high cost of single-crystal III–V substrates limits the use of gallium arsenide (GaAs) and related sphalerite III–V materials in many applications, especially photovoltaics. However, by making devices from epitaxially grown III–V layers that are separated from a growth substrate, one can recycle the growth substrate to reduce costs. Here, we show damage-free removal of an epitaxial single-crystal GaAs film from its GaAs growth substrate using a laser that is absorbed by a smaller band gap, pseudomorphic indium gallium arsenide nitride layer grown between the substrate and the GaAs film. The liftoff process transfers the GaAs film to a flexible polymer substrate, and the transferred GaAs layer is indistinguishable in structural quality from its growth substrate.
Gallium arsenide (GaAs) and related sphalerite III–V materials are attractive for a variety of electronic and optoelectronic devices; however, the high cost of III–V substrates hinders their use in certain applications, especially photovoltaics. Separating an epitaxially grown film from a III–V substrate and recycling the substrate is one means to reduce costs, and today this is achieved using an acid solution to laterally etch a sacrificial layer placed between the growth substrate and the epitaxial layer(s) of interest. This approach, however, is hindered by long etch times and possible damage to completed devices due to long immersion in etchant solution.[1–4] Inspired by our approach to control the liftoff process and location through engineering spatially dependent properties within a growth stack,[5] we describe here a new approach based on spatially controlled energy deposition from a pulsed laser. Unlike the existing techniques for separating epitaxial films of wurtzite gallium nitride (GaN) from c-plane sapphire substrates using laser-assisted GaN decomposition and subsequent Ga melt liftoff,[6–9] our approach uses spatial control of the band gap to localize laser absorption in a sacrificial layer, achieving one-step ablative liftoff of epitaxial singlecrystal sphalerite III–IV films from their substrates. It is orders of magnitude faster than the lateral etching approach, does not require long immersion in etchant solution, and allows release of completed devices. We demonstrate this approach using a common 1064 nm, nanosecond, Q-switched laser to transfer a single-crystal epitaxial GaAs film from its GaAs growth substrate to a flexible polymer substrate. Furthermore, we show that this transferred GaAs layer is indistinguishable in structural quality from its single-crystal GaAs growth substrate. Our approach achieves liftoff in a single step by causing ablation of a buried light-absorbing layer. This is in contrast to the
Data Loading...
