Energy Distribution Of Trap Density Research Articles

Determination of trap density-of-states distribution of nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films

Thin films comprising nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous-carbon (UNCD/a-C:H) composite films were experimentally investigated. The prepared films were grown on Si substrates by the coaxial arc plasma deposition method. They were characterized by temperature-dependent capacitance-frequency measurements in the temperature and frequency ranges of 300–400 K and 50 kHz–2 MHz, respectively. The energy distribution of trap density of states in the films was extracted using a simple technique utilizing the measured capacitance-frequency characteristics. In the measured temperature range, the energy-distributed traps exhibited Gaussian-distributed states with peak values lie in the range: 2.84 × 1016–2.73 × 1017 eV–1cm–3 and centered at energies of 120–233 meV below the conduction band. These states are generated due to a large amount of sp2-C and π-bond states, localized in GBs of the UNCD/a-C:H film. The attained defect parameters are accommodating to understand basic electrical properties of UNCD/a-C:H composite and can be adopted to suppress defects in the UNCD-based materials.

A new measurement technique for the characterization of carrier lifetime in thin SOI MOSFETs

We demonstrated a new application of body current to quantitative characterization of carrier lifetime in thin silicon-on-insulator (SOI) films. Previously, we have characterized the energy distribution of trap density in fully depleted (FD) SOI metal oxide semiconductor field effect transistors (MOSFETs), and furthermore, we have demonstrated that recombination at SOI/buried oxide (BOX) interface can suppress kink effect. However, little is known about electronic properties of thin SOI layers. Hence, in this study, we proposed a new electric measurement technique for characterizing recombination lifetime in thin SOI layers from body currents of MOSFETs. We investigated the dependence of inverse hole lifetime 1/ τ h on substrate bias V sub. Furthermore, we considered that the converged value gives the lifetime of bulk recombination, τ bulk, while the variation of 1/ τ h gives the lifetime of surface recombination, τ surface. We also succeeded in reproducing the tendency of 1/ τ h– V sub curves by numerical 3D device simulation. Our approach could separate the effect of bulk recombination and that of surface recombination on SOI layers.

Drift and diffusion in materials with traps

A theory of multiple trapping with an arbitrary continuous energy distribution of trap density is used to interpret time-of-flight experiments. It is shown that a so-called ‘normal’ current shape occurs if an energy distribution of localized carriers corresponds to a thermal equilibrium function, and a quasi-equilibrium carrier packet moves through a sample. If the thermal equilibrium between mobile and localized carrier fractions has not time to be established earlier than that at which most of the carriers leave the sample, the current is caused by the drift of a non-equilibrium very-dispersive carrier packet. Propagation of such a packet results in so-called ‘anomalous’ behaviour of transient current characteristics. As a result of theoretical analysis of non-equilibrium and quasi-equilibrium transient current curves, a method for interpretation of experimental transient current data is suggested. This method may provide important information on the energy distribution of localized states.