Negative-U Properties of the Deep Level E3 in ZnO Pickenhain, Rainer ; Schmidt, Matthias ; von Wenckstern, Holger ; Benndorf, Gabriele ; Pöppl, Andreas ; Böttcher, Rolf ; Grundmann, Marius Abstract Publication: Physica Status Solidi B Basic Research Pub Date: July 2018 DOI: 10.1002/pssb.201700670 Bibcode: 2018PSSBR.25500670P