PASSIVATION OF CARBON ACCEPTORS DURING GROWTH OF CARBON-DOPED GAAS, INGAAS, AND HBTS BY MOCVD

Carbon doped p-type GaAs and In0.53Ga0.47As epitaxial layers have been grown by low-pressure metalorganic chemical vapor deposition using CCl4 as the carbon source. Low-temperature post-growth annealing resulted in a significant increase in the hole concentration for both GaAs and In0.53Ga0.47As, especially at high doping levels. The most heavily doped GaAs sample had a hole concentration of 3.6 x 10(20) cm-3 after a 5 minute anneal at approximately 400-degrees-C in N2, While the hole concentration in In0.53Ga0.47As reached 1.6 x 10(19) cm-3 after annealing. This annealing behavior is attributed to hydrogen passivation of carbon acceptors. Post-growth cool-down in an AsH3/H2 ambient was found to be the most important factor affecting the degree of passivation for single, uncapped GaAs layers. No evidence of passivation is observed in the base region of InGaP/GaAs HBTs grown at approximately 625-degrees-C. The effect of n-type cap layers and cool-down sequence on passivation of C-doped InGaAs grown at approximately 525-degrees-C shows that hydrogen can come from AsH3, PH3, or H-2, and can be incorporated during growth and during the post-growth cool-down. In the case of InP/InGaAs HBTs, significant passivation was found to occur in the C-doped base region.