Electromodulation of wide-bandgap semiconductors

In this work, we explored the functionality of the electromodulation technique to determine the energy gaps of wide band gap oxides which lie in the ultraviolet region. Oxides like Er₂O₃, Ga₂O_3, HfO₂, Ta₂O₅ and ZrO₂ were analyzed in this study with their band gaps determined through the spectrophotometric as well as with the electromodulation method. Contrary to the spectrophotometric method, where extrapolation was required to find the band gap of the material, the electromodulation spectrum of each oxide clearly revealed the critical points associated with the optical transitions in the material. Keeping in view the large variations produced by the spectrophotometric method in the band gap values due to extrapolation, and the potential limitations faced by other band gap determination techniques, like electron energy loss spectroscopy, x-ray photoelectron spectroscopy and internal photoemission, in terms of their availability, demands of ultra-high vacuum and low signal to noise ratio, this study proves to be valuable in considering the electromodulation as an efficient substitute for the above mentioned experimental techniques to determine the energy gaps of wide band gap materials.