Electronic structure and effective masses of InN under pressure

Abstract

The pressure dependence of the electronic band structure of InN is investigated with emphasis on the conduction band effective mass and its dependence on free-electron concentration. Transport measurements are performed under hydrostatic pressure on three n-type samples of InN with different electron concentrations. The effective mass extracted from the electron mobility is found to increase with pressure, however with a pressure coefficient, which is lower for the samples with higher electron concentration. Calculations of the InN band structure are performed within the density functional theory by means of the linear muffin-tin-orbital method, including an empirical adjustment to reproduce known band edges at ambient pressure. The calculated variations of the highest occupied conduction band energy and the electron effective mass with free-electron concentration are compared to available experimental information. The results show a pronounced deviation from parabolic behavior of the lowest conduction band, and for k>0 this induces large differences between the values of the optical and curvature masses. Both the fundamental band gap and the electron effective mass increase with pressure, but due to the nonparabolic character of the conduction band, the pressure coefficient of the effective mass decreases with electron concentration, in agreement with the experimental observation.