Galvanomagnetic luminescence and the quantum efficiency of radiative recombination of InSb

Ion implantation is an attractive method for writing optical circuits for use in integrated optics. In LiNbO3 it is shown that there are large changes produced in both refractive indices n0 and ne by the energy deposited in nuclear collisions between the implanted ions and the lattice. The process is insensitive to ion species and at 300 K a universal curve exists for the decrease of n0 as a function of deposited energy by nuclear collisions. Saturation changes of −6% occur at 300 °K, and larger values are noted for 77 K implants. The saturation condition is reached after the deposition of ∼1022 keV cm−3 from the ion beams. Because the indices are reduced, ion beams have been used to write low index boundaries to define waveguiding regions. By using energetic light ions (e.g., 2-MeV He+) negligible change is produced in the surface layer where the energy loss is primarily electronic and thus the low index region is formed deep within the solid. The computed and measured mode characteristics are in good agreement. The guides show complex annealing characteristics but absorption losses are negligible after annealing at 200 °C. Guiding action exists after heat treatments up to some 400 °C. The surface layers retain crystallinity and electro-optic properties; as a demonstration of this we report results from three-dimensional modulators formed by helium-ion implantation.

To solve the problem of the high mercury consumption in the molecular-beam epitaxy of CdxHg l _ x Te, we present a special mercury cell and analyze the effect of the mercury flux on the cadmium and tellurium fluxes. On CdZnTe substrates, we have studied the influence of the substrate orientation on the growth defect density and the electrical properties of the epilayer. After n-type annealing, the layers have a residual doping level higher than that of the liquid phase epitaxy layers. The lower carrier concentrations are obtained on layers grown on the (310) orientation which leads to a better crystal quality than on a (100) or (111) orientation. On alternative substrates, layers grown on (100) InSb substrate are indium doped. On (100) GaAs we show that misfit dislocations can be blocked near the GaAs interface by growing a multistepped composition buffer layer (MCBL). The MCBL is a stack of CdZnTe layers with different composition. It is shown that the dislocation blocking mechanism may occur when thickness of each individual layer is below its critical thickness.

X-ray diffraction has been used to study CdTe layers grown by molecular beam epitaxy on Cd0.96Zn0.04Te or InSb substrates with either (111) or (001) orientation. The layers are elastically strained up to a critical thickness, above which misfit dislocations are generated. Our experimental determinations of the critical thickness and the relaxation of the stress while increasing the layer thickness are different from predictions of the existing models. We present a discussion of relaxation based on the determination of the minimum energy state of the layer for a given thickness. We show that above the critical thickness, the layer relaxes so that the product of the stress by the thickness remains constant. This constant has been experimentally determined for both (111) and (001) orientation.

The paper reports the formation of optical waveguides in LiNbO3 by the implantation of helium ions. The ion beam damage defines the low-index regions which surround the waveguide. The computed index profile and the observed modes are in agreement. Changes in n0 of up to 7% are recorded as a saturation index change.