ANGLE-RESOLVED PHOTOEMISSION FROM A GAAS ((1)OVER-BAR(1)OVER-BAR(1)OVER-BAR)-2X2 SURFACE - OFF-NORMAL EMISSION STUDY

Studies of angle-resolved photoemission from an As-rich GaAs(<(111)ove r tilde>)-2x2 surface hale been extended to off-normal emission. A det ailed analysis has been given of spectra taken with photon energies of 20, 23, 25, and 28 eV. The experimentally observed peak dispersion is examined using structure plots by combining free-electron final state s with initial states calculated on the basis of linear muffin-tin orb itals. The results are also compared with earlier angle-resolved photo emission studies on the same surface. This enabled us to identify emis sion features due mainly to surface states and features to which a com bination of various transitions, including surface umklapp, may contri bute.