Abstract
The physics of gallium oxide (Ga2O3) – an interesting wide bandgap semiconductor – is currently under intensive investigations within a broad research community. This interest is because of the exceptional fundamental properties of Ga2O3 giving it a huge potential for applications in power electronics and ultra-violet opto-electronics. Thus, comprehensive understanding of electrically active defects in Ga2O3 is of paramount importance.
In this talk I will report and discuss experimental data showing three previously unknown electronic states in the bandgap of β-Ga2O3.1 Most intriguingly, these deep levels were discovered under the operating conditions of the deep level transient spectroscopy measurements, that are essentially the application of a reverse bias interrupted by voltage pulses during temperature cycles up to 675 K. Combining a number of annealing tests we show that both the biasing conditions and the elevated temperature are necessary to generate these deep levels located between 1 and 2 eV from the conduction band edge. This observation of thermally activated processes stimulated by applied electric field is rather unique; as such it widens the impact of the data beyond a specific methodology in a specific material. On the other hand, we go deep into the investigation of the properties of the levels. In particular, we investigate the stability of the levels, and find that one of the levels (labeled E3*) is metastable and can be removed at similar temperatures without bias. We also determined that the E3* level is a donor, as confirmed by the Poole-Frenkel effect observation. The microscopic origin of the levels was considered and a possible scenario was discussed in terms of the reconstruction of already existing defect configurations provoked by the applied temperature and bias. As a result, the present talk, reports quite unique observation, not previously reported in other semiconductors but occurring in Ga2O3, likely because of its relatively low symmetry.
[1] M. E. Ingebrigtsen, A.Yu. Kuznetsov, B.G. Svensson, G. Alfieri, A. Mihaila, L. Vines, Phys.Rev.B, in review
Anyone interested is welcome to attend.