Heterointerface Potentials in the Effective-Mass Approximation for Wurtzite Semiconductor Structures

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In the effective-mass approximation, the step-like crystal potential of a wurtzite semiconductor heterostucture should be supplemented by Dirac delta-function heterointerface terms. They stem from the difference in the Bloch functions of the semiconductors and remain finite even for structures with graded chemical composition, where the terms are presented by a smeared Dirac delta function. We find these heterointerface potentials by employing the k*p method, and evaluate their strength from band-structure parameters of bulk materials. These potentials are weak for semiconductors compliant with the cubic approximation, which forces the zinc-blende crystal symmetry upon the wurtzite lattice. Nevertheless, they can produce a noteworthy effect due to a strong built-in electric field usually present in wurtzite heterostructures. We estimate that for GaN/AlN [0001] heterojunctions their net contributions to the energy of conduction and valence band states are 3 meV and 10 meV, respectively. The presence of the interface potential can modify the shape of the valence-band spectrum calculated without the potential.