First principles calculation of polarization induced interfacial charges in GaN/AlN heterostructures

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We propose a new method to calculate polarization induced interfacial charges in semiconductor heterostructures using classical electrostatics applied to real-space band diagrams from first principles calculations and apply it to GaN/AlN heterostructures with ultrathin AlN layers (4-6 monolayers). We show that the calculated electric fields and interfacial charges are independent of the exchange-correlation functionals used (local-density approximation and hybrid functionals). We also find the calculated interfacial charge of (6.8 +/- 0.4) x 10¹3 cm-2 to be in excellent agreement with experiments and the value of 6.58 x 10¹3 cm-2 calculated from bulk polarization constants, validating the use of bulk constants even for very thin films.