Samples which had been doped with N, to concentrations which ranged from 1018 to 2 x 1019/cm3, were characterized by using transmission electron microscopic, X-ray diffraction, and Raman spectroscopic techniques. It was found that relaxation of the mismatch-induced compressive strains between ZnSe and GaAs was less for N-doped layers at a given ZnSe thickness. The smaller amount of strain relaxation, due to N doping, produced layers which contained residual compressive strains up to a thickness of at least 1.7. In addition, the misfit dislocation array became a regular rectangular grid when N was incorporated into ZnSe layers. The ZnSe lattice constant, as measured by using X-ray diffraction, decreased with increasing N concentration. However, the reduction in lattice constant was greater than could be explained by a shorter Zn-N bond distance. The excess lattice contraction was attributed to a generation of point defects which accompanied N doping. The Raman spectra exhibited a broadening of the line-width as the N concentration increased. This supported the concept of point defect creation due to N doping.

J.Petruzzello, J.Gaines, P.Van der Sluis, D.Olego, C.Ponzoni: Applied Physics Letters, 1993, 62[13], 1496-8