Fermi level and bands offsets determination in insulating (Ga,Mn)N/GaN structures

• Published in: Scientific reports 2017-02, Vol.7 (1), p.41877-41877, Article 41877
• Main Authors: Janicki, L., Kunert, G., Sawicki, M., Piskorska-Hommel, E., Gas, K., Jakiela, R., Hommel, D., Kudrawiec, R.
• Format: Article
• Language: English
• Subjects: 639/766/119/1000; 639/766/119/2793; Band gap; Electrons; Humanities and Social Sciences; Manganese; multidisciplinary; Science
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep41877

The Fermi level position in (Ga,Mn)N has been determined from the period-analysis of GaN-related Franz-Keldysh oscillation obtained by contactless electroreflectance in a series of carefully prepared by molecular beam epitaxy GaN/Ga 1−x Mn x N/GaN(template) bilayers of various Mn concentration x . It is shown that the Fermi level in (Ga,Mn)N is strongly pinned in the middle of the band gap and the thickness of the depletion layer is negligibly small. For x  > 0.1% the Fermi level is located about 1.25–1.55 eV above the valence band, that is very close to, but visibly below the Mn-related Mn 2+ /Mn 3+ impurity band. The accumulated data allows us to estimate the Mn-related band offsets at the (Ga,Mn)N/GaN interface. It is found that most of the band gap change in (Ga,Mn)N takes place in the valence band on the absolute scale and amounts to −0.028 ± 0.008 eV/% Mn. The strong Fermi level pinning in the middle of the band gap, no carrier conductivity within the Mn-related impurity band, and a good homogeneity enable a novel functionality of (Ga,Mn)N as a semi-insulating buffer layers for applications in GaN-based heterostuctures.