Hopping conductivity and activated transport in InxGa1-xAs quantum wells A. Urbina, C. DíazPaniagua, A. F. Braña and F. Batallán Eur. Phys. J. B, 24 4 (2001) 463-468 Published online: 15 December 2001 DOI: 10.1007/s10051-001-8699-9