UC Santa Barbara

The wurtzite III-nitrides are an established set of wide-band-gap semiconductors with a wide range of applications in optical and electronic devices. Recently, new types of nitride semiconductors have been proposed to widen the range of accessible parameters and device applications. One class of such materials are the Zn-IV-nitrides, which have strong structural and electronic similarities to the III-nitrides. The predicted band gaps are desirable for optical devices operating in the visible spectrum, while the predicted band alignments to III-nitrides enable applications that are not achievable with III-nitrides alone. Another alternative nitride is ScN, which has the rocksalt crystal structure, but has a very small lattice mismatch to GaN. In this work, I thoroughly examine structural and electronic properties of these materials crucial to understanding and evaluating their application in devices.

In the Zn-IV-nitrides, we focus on ZnGeN2, which has a very close lattice match to GaN, making it the most approachable of the Zn-IV-nitrides for integration with III-nitrides. We examine the conductivity by determining the stability of native point defects and dopants. We find that, in the absence of dopants, native defects will ensure ZnGeN2 is insulating. To n-type dope the material, we find that PGe acts as a shallow donor with low formation energy. For p-type doping, we find that AlGe is a viable acceptor, with an acceptor level 0.24 eV from the valence-band maximum. However, there is strong compensation due to wrong-site doping of AlZn. This issue can be overcome by co-doping with hydrogen, and the hydrogen can be removed in a post-growth anneal. We also thoroughly examine band alignments and polarization properties among all the Zn-IV-nitrides.

Lastly, we consider interfaces between rocksalt ScN and wurtzite GaN, and show how polarization charges can be calculated at this non-polar/polar interface. We demonstrate an extremely large polarization discontinuity of –1.358 Cm−2, and propose that a ScN could be used as an interlayer in a tunnel junction device.