Heterointerface potentials in the effective-mass approximation for wurtzite semiconductor structures

摘要

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