Pressure studies of gallium nitride: Crystal growth and fundamental electronic properties

Abstract

Results of experimental and theoretical studies of the fundamental electronic properties of GaN are presented. Single crystals of GaN grown by means of an equilibrium high-pressure technique have been used for the determination of the energy gap ${\mathit{E}}_{\mathit{g}}$, refractive index n, and their pressure dependences. The electronic band structure of GaN has been calculated by means of the self-consistent linear-muffin-tin-orbital method. It has allowed us to determine the pressure variation of the measured electronic properties of GaN and to reexamine the character of ${\mathit{E}}_{\mathit{g}}$ (direct or indirect). A satisfactory agreement between the experimental and theoretical results has been obtained, and it is found that GaN is a direct-band-gap semiconductor. The pressure dependences of ${\mathit{E}}_{\mathit{g}}$ and n have been used also for comparison of GaN with other semiconductors and to examine the validity of some semiempirical schemes used for the classification of semiconductor compounds.