Effect of capping on the Dirac semimetal Cd3As2 on Si grown via molecular beam epitaxy

Given the promising applications of large magnetoresistance in the Dirac semimetal cadmium arsenide (Cd3As2), extensive research into Si-compatible Cd3As2 devices is highly desirable. To prevent surface degradation and oxidation, the implementation of a protection layer on Cd3As2 is imperative. In this study, two vastly different protecting layers were prepared on top of two Cd3As2 samples. A zinc telluride layer was grown on top of one Cd3As2 film, giving rise to a ten-fold increased mobility, compared to that of the pristine Cd3As2 sample. Interestingly, unusual negative magnetoresistance is observed in the hexagonal boron nitride-capped Cd3As2 device when a magnetic field is applied perpendicularly to the Cd3As2 plane. This is in sharp contrast to the chiral anomaly that requires a magnetic field parallel to the Cd3As2 plane. We suggest that a protection layer on molecular beam epitaxy-grown Cd3As2 should be useful for realising its great device applications in magnetic sensing.