Room-temperature Hall effect, near-infrared absorption, temperature-dependent dark current and photo-current, normalized thermally stimulated current, photoluminescence (4.2K, near-bandedge and deep-level regions), and selective pair photoluminescence (2K) methods were used to characterize undoped semi-insulating samples which had been cut from wafers that had been grown by using the low-pressure liquid-encapsulated Czochralski technique. The samples had also been subjected to 1100C annealing (fast and slow cooling), or a 1000C standard anneal. The latter clearly introduced higher concentrations of normalized thermally stimulated current traps near to 0.3 and 0.5eV, a photoluminescence center at 0.8eV, and acceptor centers which were due mainly to point defects, and which increased the resistivity. The use of slow cooling tended to reduce all of these additional centers. The selective pair photoluminescence measurements revealed changes, in the relative intensities of C-, Zn- and Si-related emissions, with changes in the annealing conditions.

Z.Q.Fang, D.C.Reynolds, D.C.Look, N.G.Paraskevopoulos, T.E.Anderson, R.L.Jones: Journal of Applied Physics, 1998, 83[1], 260-5