A theory of angle-resolved photoemission (ARPES) in doped semiconductors is developed,
paying particular attention to ARPES of the impurity band. We derive the
ARPES spectra for impurity band tails, taking into consideration various positions
of the valence band maximum on the Brillouin zone. On the basis of our theory, we
have provided a detailed analysis on the ARPES of semiconductors and have proposed
explanations for several features of the ARPES spectra taken from the cuprate superconductors.
These include sharp "quasi-particle" peaks, rapid loss of their intensities
in some directions of the Brillouin zone ("Fermi arcs") and the high energy waterfall,
which we propose is a consequence of matrix-element effects of disorder-localised
band-tails in the charge transfer gap of doped Mott-Hubbard insulators.
Our theory proposes that the ARPES intensity of cuprates near (π/2a, π/2a) is proportional
to the square of the Fourier transform component of the impurity wave-function. Our
real space image reveals some band mass anisotropy and predicts the size of the localised
state of about 10 to 20 lattice constants which justifies the "envelope" approximation
used in the impurity wave-function.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy at Loughborough University.