Effects of Zn and Ga interdiffusion on ZnSe/n+GaAs interfaces

The authors report the results of optical and electrical measurements performed on two pseudomorphic ZnSe/n+GaAs heterojunctions in which the ZnSe was grown by molecular beam epitaxy. One of the ZnSe epilayers was doped as a p-n junction using Li and Cl and dopants, with the layer adjacent to the interface doped n+; the other was unintentionally doped. Their results determine uniquely the band profiles of both samples studied. Those band profiles clearly display the effects of Zn and Ga interdiffusion, which creates strong band-bending on both sides of the interfaces and creates in the GaAs a barrier against electron diffusion into the ZnSe. The presence and size of that barrier is of primary importance for all ZnSe/GaAs device considerations. For each sample the authors measurements determine the height and depth of that barrier, the position of the bands at the interface relative to the Fermi level and the built-in field on each side of the interface. From that information the magnitude and range of the Zn and Ga interdiffusion are determined.