1. Groupe d'Etude des Semiconducteurs, Université de Montpellier 2, 34095 Montpellier, France, Institute of Physics, Polish Academy of Sciences, Al. Lotnikòw 32/46, 02-668 Warszawa, Poland, MAX-Lab, Lund University, P.O. Box 118, 221 00 Lund, Sweden, Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden, Institute of High Pressure Physics (UNIPRESS), Polish Academy of Sciences, ul. Sokołowska 29/37, 01-142 Warszawa, Poland, and FEI Company, NL-5600 MD Eindhoven,...