Enhanced Hole Generation in Mg-Doped AlGaN/GaN Superlattices Due to Piezoelectric Field

Abstract
We investigated the electrical properties of uniformly Mg-doped AlGaN/GaN superlattices (SLs) with various Al mole fractions and SL period thicknesses. We found that their sheet hole concentration depended strongly on the Al mole fraction and SL period thickness. We found the maximum spatial averaged hole concentrations for SLs with period thicknesses of 360 Å and 100 Å to be 3×1018 cm-3 at room temperature. The resistivities of the SLs were less temperature dependent than those of GaN and AlGaN, indicating that the enhanced hole generation in these SLs could be ascribed to the large energy shift of the valence band edge due to the piezoelectric field.