Increased electrical activity of Mg-acceptors in AlxGa1-xN/GaN superlattices

We grew uniformly Mg-doped AlxGa1-xN/GaN superlattices (SLs) by low-pressur e metalorganic vapor phase epitaxy and investigated the electrical properti es of these SLs parallel to the SL plane. Sheer hole concentration depends strongly on the SL period thickness and Al male fraction, and the maximum s heet concentration is 8 x 10(12) cm(-2) for AlxGa1-xN/GaN (240 Angstrom/120 Angstrom) SLs in the Al mole fraction range between 0.15 and 0.3, which co rresponds to the hole concentration of 3 x 10(18) cm(-3). One possible expl anation for this high sheet hole concentration is that the strain-induced p iezoelectric field greatly increases the electrical activity of the relativ ely deep Mg-acceptors in the SLs.