Method maps electric field of wide-bandgap semiconductor in 3D

Electronic devices based on wide-bandgap semiconductors can operate at high voltages, frequencies, and temperatures, and are especially useful in applications such as high-power electronics and particle detectors. Researchers look to further develop these devices by studying the transport properties of these materials.

For the first time, Dorfer et al. demonstrate the two-photon absorption edge transient current technique on a wide-bandgap semiconductor to map the material’s charge carrier transport properties.

The authors pulsed a femtosecond laser into a sample of synthetic single-crystal diamond, which is a wide-bandgap semiconductor. The laser caused the diamond to absorb photons and generate charge carriers in the sample. As the charge carriers moved with the electric field, a transient current pulse was formed. By scanning the laser across the sample and analyzing the transient currents, the authors were able to obtain a 3D map of the electric field and charge carrier transport in the sample.

Christian Dorfer, one of the authors, said this mapping technique could be used to probe the insides of wide-bandgap semiconductor devices during operation, which can help one better understand the charge properties of impurities in the material and ultimately finetune these devices.

In addition, the authors also noticed a correlation between the measured electric field map and the structural defects observed via X-ray topography in their diamond sample. Further studying this correlation may reveal how structural defects and impurities in diamond affect its electric field. The team have begun work on a more systematic study of how structural defects affect charge trapping and space charge formation.

Source: “Three-dimensional charge transport mapping by two-photon absorption edge transient-current technique in synthetic single-crystalline diamond,” by C. Dorfer, D. Hits, L. Kasmi, G. Kramberger, M. Lucchini, M. Mikuž, and R. Wallny, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5090850 .