Selective epitaxial growth of In1-xAlxAs by metal-organic vapour-phase epitaxy

Highly selective epitaxy (HSE) of AlAs, In1−xAlxAs and InAs has been successfully demonstrated for wide (about 200 μm) passivation masks by introducing a small quatity of HCl gas into a conventional metal-organic vapour-phase epitaxy process. We have used two thermodynamic models to evaluate the role of HCl gas in achieving high selectivity. Two factors leading to the improvement in selectivity caused by the introduction of HCl gas were considered: (1) reduction of gas-phase supersaturation of growth species; (2) inhibition of the reaction between the growth species and the mask. It is thought that the inhibition of the surface reaction results from termination of the dangling bonds on the SiNx surface by Cl and H and the inhibition enhances the surface diffusion. The effective role of HCl in the HSE of Al-containing compounds can be explained by this inhibition effect.