Ultra-near-surface gallium-activated 435 nm luminescence from donor-acceptor-pair recombination in ion-beam implanted 4H-SiC

Nitrogen and gallium-doped SiC and its luminescence properties are investigated in detail. Spatially highly localized gallium doping is realized by ion implanting Ga into n-type 4H SiC using an ion milling tool for the first time. A nanoscale depth region of Ga-rich SiC is formed near the SiC surface, followed by 1600 °C activation annealing. An AlN capping layer is used to avoid the out-diffusion of Ga, stabilize the SiC surface, and serve as an additional source of N dopant. An emission spectrum with a peak wavelength of approximately 435 nm at room temperature is identified and confirmed to be due to Ga-N donor-acceptor-pair recombination. Photoluminescence, cathodoluminescence, SEM and TEM results are presented. It is thereby shown that the more conventional p-type dopant Al can be replaced by Ga, enabling high-intensity Taylor cone gallium ion sources to achieve highly spatially controlled donor-acceptor pair emission from SiC. Several aspects of the relevance of spatially localized donor-acceptor pair emission are described.