Antonova I.V.,RAS Semiconductor Physics Institute |
Popov V.I.,North West Federal University |
Smagulova S.A.,North West Federal University |
Jedrzejewski J.,Hebrew University of Jerusalem |
Balberg I.,Hebrew University of Jerusalem
Journal of Applied Physics | Year: 2013
The present study of deep level transient spectroscopy (DLTS) is focused on a comparison of the trap states in two types of Ge nanocrystallites (NCs)-insulator composites. The investigated systems were the dielectric matrices Al2O3 and SiO2 in which the Ge NCs were embedded. We have found couples of traps with related values of activation energies in both the Ge:Al2O3 and the Ge:SiO2 films. In the films with a relatively low Ge content (where only small NCs sized 3-5 nm could have been detected by means of Raman spectroscopy), we observed traps with an energy level ∼50 meV in the Ge:Al2O3 films and 120 and 50 meV in the Ge:SiO2 films. In both systems, we found that the electron traps have a small carrier capture cross-section (10-21-10-23 cm2). We have identified the levels of the traps to be the quantum confinement levels in the small Ge NCs. For samples of higher Ge contents, where the NC size reaches about 20 nm and where an appreciable portion of the dielectric matrix consists of amorphous Ge (α-Ge), we found traps with an energy of 0.22-0.24 eV in the Ge:Al 2O3, and 0.26-0.27 eV in the Ge:SiO2 samples. We suggest that this peak in the charge DLTS (Q-DLTS) spectra is associated with a trap at the Ge-NC/α-Ge interface. We have also identified the energy position of a defect level in the Ge:Al2O3 layers, which lies 0.46-0.49 eV below the conduction-band edge of the Si substrate. © 2013 American Institute of Physics.