Resonant electron tunneling in GaN/Ga_{1 - x}Al_xN(0001) strained structures with spontaneous polarization and piezoeffect

Electron tunneling through the GaN/Ga_{1 - x}Al_xN(0001) wurtzite strained structures is investigated by the pseudopotential and scattering matrix methods. It is shown that the results of multiband calculations at low aluminum concentrations (x <0.3) are adequately described within the single-valley model in the envelope wave function method accounting for the dependences of the effective mass on the energy and strain. Upon electron tunneling through two-barrier structures, sharp resonance peaks are observed at a barrier thickness of several monolayers and the characteristic collision time in the resonance region is equal to ∼1 ps. The internal electric fields associated with spontaneous and piezoelectric polarizations lead to a "red" or "blue" shift in the resonance energy according to the thickness and location of barriers with respect to the polar axis. In the (GaN)_n(Ga_{1 - x}Al_xN)_m superlattices, the internal fields can form the Stark ladder of electronic states at a small number of ultrathin layers even in the absence of external fields.