Experiments in MIS structure based on germanium and improvements of the interfacial properties

In the fast-moving electronics area, the studies of the germanium metal-ins ulator-semiconductor (MIS) devices are of wide interest. For the elaboratio n of the germanium MIS structures, alumina films with 2000 Angstrom thickne ss were deposited on thermally grown germanium oxide films as well as on cl ean germanium surfaces. The electrical measurements of Al2O3/Ge structures indicate a high density of states and consequently, a bad electronic qualit y of the MIS structures. On the other hand, we show that the presence of th e germanium oxide layer GeO2 (30 Angstrom) between alumina and germanium re duces the density of states. This effect is due to the protection of the ge rmanium surface during the deposition of alumina film and probably at the i mprovement of alumina adhesion. To improve the performances of our germaniu m MIS structures and to optimize the annealing conditions, we have employed 'forming-gas' [N-2 : H-2 = 85% : 15%] annealing of Al2O3/Ge and Al2O3:GeO2 /Ge structures at different temperatures. After 30 min of annealing at T = 400 degrees C, the density of states at the interface has bran evaluated at 5 x 10(10) eV(-1) cm(-2). (C) 2000 Elsevier Science S.A. All rights reserv ed.