Electron mobility in wurtzite nitride quantum wells limited by optical-phonons and its pressure effect

摘要

Based on the dielectric continuum phonon model, uniaxial model and force balance equation the mobility of two dimensional electron gas in wurtzite AlxGa1-xN/GaN/AlxGa1-xN quantum wells is discussed theoretically within the temperature range dominated by optical phonons. The dependences of the electron mobility on temperature, Al molar fraction and electron sheet density are presented including hydrostatic pressure effect. The built-in electric field is also taken into account. It is found that under normal pressure the main contribution to the mobility is from the scattering of interface optical phonons in narrow (for well width d < 12 -A) and wide (for d > 117 -A and d > 65 -A for finitely thick barriers and infinitely thick ones, respectively) wells, whereas that is from the scattering of confined optical phonons in a well with an intermediate width. It is shown that the electron mobility decreases with increasing Al molar fraction and temperature, whereas increases obviously with increasing electron sheet density. The theoretical calculated electron mobility is 978 cm2/V s which is higher than an available experimental data 875 cm2/V s when x equals to 0.58 at room temperature. The results under hydrostatic pressure considering the modification of strain indicate that the mobility increases slightly as hydrostatic pressure increases from 0 to 10 GPa.