Low pressure MOCVD growth of buried heterostructure laser wafers using high quality semi-insulating InP

Abstract

Semi-insulating Fe doped InP has been grown by low pressure MOCVD at 100 mbar and 630° C. Complete activation of Fe below the solubility limit of 5 × 1016 cm-3 has been achieved by reducing the PH3 concentration during crystal growth to the lowest value required to maintain good surface morphology of the layer. Diffusion of the Fe dopant and dopant spikes at the interface between the substrate and grown layer can be minimized by ensuring that the total Fe concentration in the layer does not exceed the diffusion threshold of 2 × 1017 cm−3. Growth of Fe doped InP around a double heterostructure mesa formed by reactive ion etching produces a structure without either growth of InP on the mesa or notches at the mesa sidewalls, even with minimal overhang of the dielectric mask. Examination of regrown heterostructures shows no evidence of interdiffusion of Fe and Zn, indicating that Fe diffusion has been successfully prevented. Completed lasers have threshold current densities of 2.5 kA/cm2 at 20° C and initial aging results which indicate that these devices have good lasing characteristics and potentially high reliability.