Polarization induced hole doping in graded AlxGa1-xN (x = 0.7 ∼ 1) layer grown by molecular beam epitaxy

摘要

Polarization induced hole doping on the order of ∼1018 cm-3 is achieved in linearly graded AlxGa1-xN (x = 0.7 ∼ 1) layer grown by molecular beam epitaxy. Graded AlxGa1-xN and conventional Al0.7Ga0.3N layers grown on AlN are beryllium (Be) doped via epitaxial growth. The hole concentration in graded AlxGa1-xN:Be (x = 0.7 ∼ 1) layers demonstrates that polarization generates hole charges from Be dopant. The Al0.7Ga0.3N layer is not conductive owing to the absence of carriers generated from the Be dopant without the inducement of polarization. Polarization doping provides an approach to high efficiency p-type doping in high Al composition AlGaN.