Passivation of P-Type Dopants in GaAs by Process Induced Hydrogenation and Reactivation by Thermal Annealing

The sheet-resistance of a carbon-doped p-type GaAs epitaxitial layer was increased by silicon nitride plasma-chemical-vapor-deposition (PCVD) using SiH4 and N2 gases. This increase was strongly correlated with the increase in hydrogen concentration in the GaAs epitaxial layer, suggesting that the acceptor arising from the carbon impurity is passivated by hydrogenation during silicon nitride deposition. Thermal annealing in N2 gas at 500°C reactivated the passivated acceptor. On the other hand, acceptor passivation was not observed for beryllium-doped p-type GaAs under the same process conditions. The difference in behavior between carbon and beryllium may be due to the difference in dissociation energy of hydrogen-dopant complexes.