No abstract

Contact less measurements of the minority carrier “lifetime” and the photoconductivity are widely used to characterize the material quality and to investigate defects in a sample. In order to interpret these measurements correctly and to guarantee comparability between different methods, numerical simulation tools were developed. These simulations allow to account even for very complex defect models, thus, e.g., enabling the simulation of trapping effects. Contrary to the Shockley–Read–Hall model or the widely used simulation tool PC1D nearly no assumptions are made. Furthermore, nonsteady state solutions can be obtained. The simulation approach is explained in detail, along with simulations of the trapping effect on the measured lifetime for different injections, trap parameters, and measuring methods, demonstrating the capabilities of the here presented simulation tool. Temperature and injection dependent lifetime measurements were performed and it is shown how important sample parameters can be extracted using the simulation tool. Additionally an approach is presented to simulate lifetimes for thick samples, where a nonuniform carrier profile has to be taken into account. This enables a comparison of nonsteady state to steady-state lifetime measurement techniques even for thick samples such as ingots.

The novel technique microwave detected photo induced current transient spectroscopy (MD-PICTS) was applied to semi-insulating 6H-SiC in order to investigate the properties of inherent defect levels. Defect spectra can be obtained in the similar way to conventional PICTS and DLTS. However, there is no need for contacting the samples, which allows for non-destructive and spatially resolved electrical characterization. This work is focused on the investigation of semi-insulating 6H-SiC grown under different C/Si-ratios. In the corresponding MD-PICTS spectra several shallow defect levels appear in the low temperature range. However the peak assignment needs further investigation. Additionally different trap reemission dynamics are obtained for higher temperatures, which are supposed to be due to different compensation effects.

No abstract

No abstract