ABSTRACT
This chapter reviews the experimental measurements which have established the present-day picture of the band structure. Additional information about the band structure is obtained from luminescence measurements, excitation of electrons from the valence band to the conduction band. In many semiconductors with an indirect band gap on a cube axis the band gap decreases with increasing hydrostatic pressure. Measurements of the energy of the direct band gap and higher energy inter- and intraband transitions can only be made using reflectivity measurements since diamond is strongly absorbing in this region. Absorption and luminescence studies reveal well over 100 electronic transitions at defect centers in diamond. Boron forms an acceptor in diamond and gives rise to optical absorption, electrical conductivity and photoconductivity. The chapter discusses the determination of the effective masses of positive holes which gives some additional information about the structure of the valence bands.
