Figure 1
From: Increased static dielectric constant in ZnMnO and ZnCoO thin films with bound magnetic polarons
Schematic representation of charge distribution in the n-ZnO layer, the Si3N4 layer and the p-Si in the metal/n-ZnO semiconductor/Si3N4 insulator/p-Si semiconductor (MSIS) structure and corresponding band diagram in (a) accumulation (b) depletion and (c) inversion. There are mirror charges on Al top electrode to compensate the charges in p-Si accumulated at the interface Si3N4/p-Si. There are singly ionized oxygen vacancies in accumulation and depletion and single and double ionized oxygen vacancies in inversion in ZnO. The majority charge carriers are accumulated at the opposite interface of the ZnO layer. Si3N4 contains both mobile (~) and fixed (▫) positively charged impurities. The existence of the positive impurity charges are expected from the shift of the flat-band voltage towards more negative biases in the negative bias range. Due to the thickness (~110 nm) of the n-type ZnO thin film, only fully depleted or fully accumulated regime band diagram is shown in the figure. Work function of ΦM for aluminium metal is 4.3 eV, electron affinity of ZnO χZnO is 4.2 eV, electron affinity of Si3N4 χi is 1.8 eV and electron affinity of p-Si χs is 4.15 eV. Band gap of ZnO \({{\rm{E}}}_{g}^{ZnO}\) is 3.3 eV, band gap of p-Si \({{\rm{E}}}_{g}^{Si}\) is 1.1 eV and bulk potential φb of p-Si is 0.36 eV.
