Electron mobility in polarization-doped AI_(0-0.2)GaN with a low concentration near 10~(17) cm~(-3)

摘要

In this letter, carrier transport in graded Al_xGa_(1_x)N with a polarization-induced n-type doping as low as ~10~(17)cm~(-3) is reported. The graded Al_xGa_(1-x)N 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 AI composition from 0% to 20% over a thickness of 600 nm. A compensating center concentration of ~10~(17)cm~(_3) was also estimated. A peak mobility of 900 cm2/ V•s at room temperature is extracted at an Al composition of which represents the highest mobility achieved in n-Al_(0.07)GaN with a carrier concentration of ~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 <10~7cm~(-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,