THE EFFECT OF RAPID THERMAL ANNEALING AND HYDROGENATION OF NTD GAAS IRRADIATED WITH NEUTRONS

Photoluminescence (PL) spectra as a function of rapid thermal annealin g (RTA) temperature are measured for semi-insulating undoped GaAs irra diated with low- and middle-level neutrons and also after hydrogenatio n. In the case of the irradiation with low-level neutrons, C(B-A) and Ge(B-A) peaks at 800-degrees-C increase remarkably, and C(D-A) and Ge( D-A) peaks appear weakly together with C(B-A) and Ge(B-A). The intensi ty of Ge(B-A) transitions is almost comparable to that of C(B-A) trans itions as the carbon concentrations in GaAs wafers (usually almost-equ al-to 10(15) cm-3) are competitive with the transmuted Ge concentratio ns estimated from doping (almost-equal-to 10(15) cm-3). After hydrogen ation, Ge(B-A) peaks decrease and C(D-A), Ge(D-A) peaks disappear due to the passivation by hydrogen. In the case of irradiation with middle -level neutrons the Ge(B-A) peaks including Ge(D-A) increase significa ntly, and C(B-A) peaks are concealed by Ge(B-A) peaks because the Ge c oncentrations (almost-equal-to 10(16) cm-3) transmuted by the irradiat ion of middle-level neutrons exceed the carbon concentrations in the G aAs wafer. After exposure of the same samples to a hydrogen plasma, Ge (B-A) peaks decrease apparently due to passivation. When furnace annea ling was carried out for the same sample irradiated with middle-level neutrons, the V(As)-C(As) defect complex center is observed around 879 nm because of the influence of the carbon susceptors. In the present study, the V(As)-C(As) defect complex is not observed after RTA. There fore, it is confirmed that the V(As)-C(As) defect complex appearing af ter furnace annealing is correlated with carbon in the sample holder d uring the thermal treatment.