Bandedge and Optical Functions of InN

The theoretical calculations of the band structure of InN can be grouped into semi-empirical (pseudopotential [10-12] or tight binding [13,14]) ones and first principles ones [15-22], In the former, form factors or matrix elements are adjusted to reproduce the energy of some critical points of the band structure. In the work of Jenkins et al [14], the matrix elements for InN are not adjusted, but deduced from those of InP, InAs and InSb. The bandgap obtained for InN is 2.2 eV, not far from the experimentally measured value. Interestingly, these authors have calculated the band structure of zincblende InN, and have found the same bandgap value [14]. 

TABLE 2 Theoretical spin orbit and crystal field terms appearing in EQN (1) for InN. 

TABLE 2 shows that, as in GaN, these terms are weak, and that the three uppermost valence bands in InN are expected to lie within a few tens of meV. 

InN is at the present time always grown n-type, and this has allowed experimental determinations of the electron effective mass from plasma reflectivity [4,8,24], Hole masses are generally obtained from band structure calculations. TABLE 3 lists some determinations of electron and hole masses of InN in units of mo. Most calculations agree with the experimental electron mass of 0.1 lmo, but the uncertainty regarding hole masses is still large at the present stage. 

TABLE 3 Electron and hole effective masses in InN in units of mo. 

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