Two-Dimensional Carrier Gas at a Polar Interface without Surface Band Gap States: A First-Principles Perspective*

We present first principles calculations of the interface between GaN and strained AlN, using a slab model in which polarization is compensated via surface fractional-charge pseudo-hydrogen atoms^[1]. This slab approach produces results that are in agreement with the prediction of the modern theory of polarization. Upon natural extension to an interface, it shows that an interfacial two-dimensional carrier electron or hole gas emerges naturally in response to different compensating surface charges, but that this need not involve in-gap surface states.

 

^[1] Brivio et al., Appl. Phys. Lett. 123, 022104 (2023).