Interdiffusion and conversion of InP/In0.53Ga0.47As superlattices induced by p-type dopants

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Abstract
Zn diffusion into an unstrained InP/In0.53Ga0.47As superlattice has been observed to result in the formation, first, of a strained layer In1−xGaxP/In1−xGaxAs supperlattice due to the selective diffusion of In and Ga, then a Zn3P2/In1−xGaxAs superlattice due to ‘‘kickout’’ of the cations, and finally a Zn3P2/Zn3As2 superlattice. The lateral confinement of Zn induced interdiffusion and conversion is examined by diffusing through a 3 μm period Si3N4 grating. The effects of Cd diffusion and Be ion implantation are also examined. Organometallic chemical vapor deposited InP/In0.53Ga0.47As superlattices were diffused at 600 or 650 °C in sealed ampoules with Zn3As2 or Cd3P2 powder as the dopant source. Samples were examined by secondary ion mass spectrometry and analytical electron microscopy. In the grating experiment, cation homogenization resulted in the formation of a uniform unconfined strained layer superlattice with superior surface quality in the regions protected by Si3N4. Zn3P2 superlattice conversion was confined within the grating window regions; however, a thick unconfined Zn3P2 layer was observed to form below the superlattice. A Ga concentration spike was present between this thick Zn3P2 layer and the underlying substrate. Cd was less efficient at intermixing the superlattice, owing largely to its relatively low solubility and diffusion coefficient. Partial intermixing was induced by Be implantation, with Be segregation into the InP layers observed near the implant peak.

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