Das Projekt "Untersuchung zur Anwendbarkeit des Ionenclusterstrahldepositionsverfahrens fuer Duennfilm-Gassolarzellen" wird vom Umweltbundesamt gefördert und von Battelle-Institut e.V. durchgeführt. Objective: Gas thin film solar cells have shown their potential for high efficiency above 10 per cent. They are considered for components in tandem solar cells. Problems have been found regarding deposition temperatures crystallite configuration and grain boundaries. It is the aim of the proposed work to demonstrate that a new, ion-assisted deposition process, 'ion cluster beam' deposition (ICB) can lead to significantly improved gas thin film solar cells at lower substrate temperatures than needed in the past. In ICB deposition the material, e.g. Ga and As is transported towards the substrate in the form of small clusters containing approx. 100 atoms, which are charged by electron beam and accelarated towards the substrate by an electric field. The kinetic energy of the arriving clusters, decomposing into atoms, represents a 'virtual temperature', facilitating reaction and crystallite growth. General Information: Gas deposition technologies recently have found increased interest under the aim of monolithically integrating Gas and Si technologies for electronic and optoelectronic applications. This will also influence gas thin film solar cell development efforts. The potential for achieving above 10 per cent efficiency for polycrystalline films, close to 20 per cent fro films on Si and Ge and well above 20 per cent for films on bulk gas has recently been demonstrated. It is the aim of the project to deposit gas films by means of the 'ionized cluster beam' deposition process, and to optimize them insofar, that films suited for solar cell application can be obtained at lowest possible substrate temperatures. The process has been defined so, that in the first phase Ga will be deposited by ICB and as will be coevaporated as element. The components for the process have been purchased, developed and built. After individual tests they have been installed within the vacuum vessel. Gas films have been deposited onto commercial gas wafers at temperatures of 580 C under excess as-flux at a deposition rate of 2a/s. Main parameter to be varied has been the acceleration potential for the ionized clusters. First optimisation steps have led to epitaxial films on gas having p-doping levels as low as 10e12cm-e3 and hole mobilities of up to 250CME2V-1S-1, as determined from films grown on high-resistivity wafers.