Unintentional redistribution of Zn in InGaAsP/InP heterostructures

The unintentional redistribution of Zn during annealing of InGaAsP/InP:Zn heterostructures at 650 to 724 degrees C was investigated. An abrupt increase of the hole concentration p was observed in the quaternary alloy while in the vicinity of the heterointerface the adjacent InP layer exhibited values of p which are by up to an order of magnitude lower than in the bulk. Both effects adversely affect the performance of double-heterostructure laser diodes. Numerical simulations taking Zn diffusion via monovacancy and divacancy complexes in addition to the common substitutional-interstitial mechanism into account indicate that a considerable number of immobile monovacancy complexes are incorporated into the InP during epitaxy. The mobile divacancy complex, which is in equilibrium with the monovacancy complex, penetrates the quaternary layer where it is incorporated as an electrically active impurity.