Electron Mobility In Polarization- Doped Al0-0.2gan With A Low Concentration Near 10(17) Cm(-3)

In this letter, carrier transport in graded AlxGa1-xN with a polarization-induced n-type doping as low as similar to 10(17) cm(-3) is reported. The graded AlxGa1-xN is grown by metal organic chemical vapor deposition on a sapphire substrate, and a uniform n-type doping without any intentional doping is realized by linearly varying the Al composition from 0% to 20% over a thickness of 600 nm. A compensating center concentration of similar to 10(17) cm(-3) was also estimated. A peak mobility of 900 cm(2)/V.s at room temperature is extracted at an Al composition of similar to 7%, which represents the highest mobility achieved in n-Al0.07GaN with a carrier concentration of similar to 10(17) cm(-3). A comparison between experimental data and theoretical models shows that, at this low doping concentration, both dislocation scattering and alloy scattering are significant in limiting electron mobility and that a dislocation density of <10 (7) cm(-2) is necessary to optimize mobility near 10(16) cm(-3). The findings in this study provide insights into key elements for achieving high mobility at low doping levels in GaN, a critical parameter in the design of novel power electronics taking advantage of polarization doping. Published by AIP Publishing.