MISFIT DISLOCATION NUCLEATION IN DOPED AND UNDOPED ZNSE GAAS/

We have observed that undoped ZnSe films grown on GaAs substrates by m olecular beam epitaxy show an irregular array of interfacial 60-degree s misfit dislocations. However, N and Cl doping of the ZnSe thin films changes the interfacial dislocation structure. p-type ZnSe with N con centrations of approximately 10(18)/cm3 shows a regular array of inter facial 60-degrees misfit dislocations and a lower (approximately 1 X 1 0(6)/cm2) density of threading dislocations compared to undoped films. However, samples with doping levels higher than 10(19)/cm3 show a den sity of threading dislocations of approximately 10(8)/cm2. These diffe rences are explained in terms of Frank partial dislocations observed o nly in doped ZnSe. The Frank partial dislocations act as nucleation si tes for the misfit dislocations. Thus, different mechanisms for the fo rmation of misfit dislocations in doped and undoped films occur in thi s system.