Evaluation of the electronic states in highly Ce doped Si films grown by low temperature molecular beam epitaxy system

Highly Ce doped single crystalline Si films with high crystallinity, smooth surface and uniformly distributed Ce were deposited by low-temperature grown molecular beam epitaxy (LT-MBE) system. The lattice parameter increases with increasing Ce concentration below 0.2 at%, suggesting that the formation of substitutionally dissolved Ce increases. The donor level of Si homoepitaxial film without Ce doping is calculated as 57 meV originated in the formation of dangling bonds probably due to low temperature growth. Although all films show n-type conduction, electron density decreases with increasing the Ce concentration below 0.5 at%, suggesting Ce3+ ion at substitutional site in Si acts as an acceptor. However, the conduction type does not change from n-type to p-type, indicating that the density of the Ce3+ ion is not enough to change the conduction type. J-V characteristics at the measurement temperature from 180 to 300 K were evaluated by using metal-insulator-semiconductor (MIS) structure. The generation energy of electron-hole pair is calculated by Arrhenius plot of resistance at depletion layer. The charged state at the mid gap in Si is formed by Ce doping.