Theory of InN bulk band structure
Indium nitride (InN) is a key material for GaN-based light-emitting devices, since InN incorporation is necessary for adjusting the near ultraviolet pure-GaN band gap to the blue spectral region [8.1]. Despite the technological importance of InN, its fundamental physical parameters were controversial until about 2005 [8.2, 8.3]. In the 1970s and 1980s, the direct band gap of InN was estimated as being approximately 2 eV [8.4, 8.5]. Among the group-III nitrides InN remained the most mysterious compound due mainly to the difficulty in growing high-quality crystals because of the extremely high equilibrium vapor pressure of nitrogen. Early absorption measurments were therefore restricted to polycrystalline films grown by DC discharge [8.4], reactive cathodic sputtering [8.6], RF sputtering [8.5, 8.7], or metalorganic vapor phase epitaxy (MOVPE) [8.8].