EFFECT OF HIGH-TEMPERATURE ANNEALING ON ELECTRICAL AND OPTICAL-PROPERTIES OF UNDOPED SEMIINSULATING GAAS

A comprehensive characterization, including room temperature Hall effe ct, near infrared absorption, temperature dependent dark current and p hotocurrent (using 1.13 eV light), normalized thermally stimulated cur rent (NTSC), photoluminescence at 4.2 K in both near band edge and dee p level regions, and selective pair photoluminescence (SPL) at 2 K, ha s been carried out on undoped semi-insulating GaAs samples, cut from f our wafers which were grown by the low pressure liquid encapsulated Cz ochralski technique and annealed by three different schedules: a 1100 degrees C anneal with either fast or slow cooling, or a 1000 degrees C standard anneal. The 1100 degrees C anneal clearly introduces higher concentrations of NTSC traps near 0.3 and 0.5 eV, a PL center at 0.8 e V, and acceptor centers, which are mainly due to the point defects and increase the resistivity. Slow cooling to some extent reduces all of these additional centers. The SPL measurements show changes in the rel ative intensities of C, Zn, and Si related emissions with changes in a nnealing conditions. (C) 1998 American Institute of Physics.