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Cu(In, Ga)Se 2 thin films were deposited on Mo/soda-lime glass substrates by the one-stage co-evaporation process at the substrate temperatures (T sub ) from 350 • C to 550 • C. The structural and electrical properties of CIGS films have been studied by x-ray diffraction (XRD), scanning electron microscopy (SEM) and Hall effect measurement. The experimental results indicate that a temperature of 450 • C is critical for CIGS films grown by the one-stage process. The (In, Ga) 2 Se 3 phase with high resistivity is found below this temperature. The higher T sub will lead to the formation of single-phase CIGS films with larger grain size and better electrical properties. A higher carrier concentration and lower resistivity of CIGS films are ascribed to sodium incorporation diffused from the glass substrate and the disappearance of the (In, Ga) 2 Se 3 phase in CIGS films. Additionally, the performance of the CIGS solar cells improves significantly with the increase of T sub . It can be attributed to the reduction of the grain-boundary recombination and the sufficient reaction between the additional (In, Ga) 2 Se 3 phase and the Cu x Se y binary phase at T sub above 500 • C.

In order to reduce substrate cost and produce integrated III-V semiconductor device structure, porous InP layer was formed on an InP substrate to be used a mechanically weak layer to assist lift-off of subsequent epitaxial grown layer which need to be transferred onto another substrate. This process follows the work done for ELTRAN (Epitaxial Layer TRANsfer) in the silicon material system(1). In this work, electrochemical etching was used to fabricate a dual porous layer and the sample was annealed to reconstruct porous structure and get ready for epitaxial deposition. The result of bonding and transferring process leaves a 2 μm InP layer on PDMS substrate, and it indicates promising application in flexible optoelectronics.

High crystalline quality InP is epitaxially grown on porous InP layers and characterized. Etching the wafers in hydrochloric acid with different concentrations and current densities create a dual layer porous structure with a more dense top layer for epitaxial growth and a buried porous layer. Annealing the structure forms voids in the buried layer. Epitaxial layers with thickness of about 2 µm were grown on dense layers. The layers grown were analyzed by transmission electron microscopy and high resolution x-ray diffraction and determined to be high quality single crystal layers. The porous samples created were bonded to PDMS substrates and the top layer was easily peeled off due to fracture through the high porosity layer. Layer transfer was also performed by gluing the samples to glass slides and pulling them apart. The transferred layers were characterized by scanning electron microscopy. These results point to the usefulness of porous III-V layers as templates for epitaxial growth and device transfer.