Shining the spotlight on defects in ß-Ga2O3

Abstract: Ideal power electronic devices like transistors and diodes would act like conventional switches; toggling between zero and infinite resistance states. Wide and ultrawide bandgap semiconductors can hold off large voltages over small distances in the off state, while the ability to dope the material reduces resistivity for the on state. Monoclinic b-Ga2O3 with 4.8 eV bandgap has recently become available in bulk crystal form and is a promising candidate for high voltage devices. Critical to enabling applications foreseen for bGa2O3 is understanding and controlling point defects and doping.

My research group has investigated the effects of impurity defects have on carriers, such as photoluminescence from Cr and Fe and trapping and emission at deep defects. We find that the crystalline anisotropy, resonant energy level transfer, and field assisted tunneling modify these carrier-defect interactions. More recently, we have begun investigating how carriers can be utilized to affect the types and concentrations of defects themselves; by illuminating Ga2O3 during annealing we show we can modify the ensembles of point defects present. In this ongoing work, we show using deep level transient spectroscopy that the types and densities of defects present can be modified in b-Ga2O3 with moderate below-bandgap light fluences even at 1000 oC. The combination of somewhat weak light absorption and ultrawide bandgap make Ga2O3 an excellent material for investigating a range of light-defect couplings that can be exploited to achieve practical material processing goals such as suppressing compensating defect concentrations. These results show clearly that, in terms of especially native defects which govern doping and mobility, semiconductor processing at a given temperature supplied by radiative heating using incandescent or other light sources is qualitatively different from processing using conductive heating.

Bio: Mike Scarpulla is an Associate Professor in the departments of Materials Science & Engineering and Electrical & Computer Engineering at the University of Utah. His research group specializes in processing, defects, and characterization in compound semiconductors for photovoltaics and energy efficiency. Prior to joining the University of Utah he was a postdoc at UC Santa Barbara and completed his PhD at UC Berkeley.

Additional Information:

Please contact Lisa Spicer at lms8@psu.edu for Zoom information.