Electron Mobility in Polarization-doped Al$mathrm{_{0-0.2}}$GaN with a Low Concentration Near 10$mathrm{^{17}}$ cm$mathrm{^{-3}}$

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Abstract

In this letter, carrier transport in graded Al$\mathrm{x}$Ga$\mathrm{{1-x}}$N with a polarization-induced n-type doping as low as ~ 10$\mathrm{^{17}}$cm$\mathrm{^{-3}}$is reported. The graded Al$\mathrm{x}$Ga$\mathrm{{1-x}}$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 Al composition from 0% to 20% over a thickness of 600 nm. A compensating center concentration of ~10$\mathrm{^{17}}$cm$\mathrm{^{-3}}$was also estimated. A peak mobility of 900 cm$\mathrm{^2}$/V$\mathrm \cdot$s at room temperature is extracted at an Al composition of ~ 7%, which represents the highest mobility achieved in n-Al$\mathrm{_{0.07}}$GaN with a carrier concentration ~10$\mathrm{^{17}}$cm$\mathrm{^{-3}}$. 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$\mathrm{^7}$cm$\mathrm{^{-2}}$is necessary to optimize mobility near 10$\mathrm{^{16}}$cm$\mathrm{^{-3}}$. The findings in this study provide insight in key elements for achieving high mobility at low doping levels in GaN, a critical parameter in design of novel power electronics taking advantage of polarization doping.

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https://arxiv.org/abs/1704.03001

PDF

https://arxiv.org/pdf/1704.03001