Effects of a finite melt on the thickness and composition of liquid phase epitaxial InGaAsP and InGaAs layers grown by the diffusion-limited step-cooling technique

The thickness of InGaAsP (λg=1.15 μm) and InGaAs (λg=1.68 μm) liquid phase epitaxial layers grown on (100) InP substrates by the step-cooling technique has been measured as a function of growth time. (λg is defined as the wavelength corresponding to the energy gap of the epitaxial layer.) For growth times much less than the shortest diffusion time τi=l2/Di of the melt constituents, where l is the melt height and Di is the diffusivity of each component in the melt, the thickness is consistent with diffusion-limited theory, and the composition is constant. The time at which the growth rate deviates sharply from diffusion-limited theory and beyond which constant composition growth can no longer be maintained has been determined for the melt size used in our experiments and can be estimated for any melt size.