Effect of Capping on the Dirac Semimetal CdAson Si Grown Via Molecular Beam Epitaxy

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