EVALUATION OF LOW-TEMPERATURE INTERDIFFUSION COEFFICIENTS IN HG-BASEDSUPERLATTICES BY MONITORING THE E-1 REFLECTANCE PEAK

We show that variations of the E-1 reflectance peak in Hg-based superl attices can be used to probe low-temperature interdiffusion by monitor ing the shift of the E-1 peak wit time-over extended periods. Little e vidence of interdiffusion was detected for a number of HgTe/CdTe and H gCdTe/CdTe superlattices stored at room temperature for approximately two years. Two HgTe/CdTe superlattices and one HgCdTe/CdTe superlattic e were subsequently annealed in a dry nitrogen atmosphere at 100 degre es C for approximately six months, and then at 150 degrees C for 24 da ys. During these intervals, the superlattices were periodically remove d from the anneal for reflectance measurements to assess the extent of the interdiffusion. Comparison of these results with calculations of superlattice bandgaps and interdiffusion profiles has led to an evalua tion of the low temperature interdiffusion coefficients. These extend previous results to lower temperatures and confirm that the degradatio n of Hg-based superlattices devices due to thermal interdiffusion unde r normal processing, storage, and operating conditions should not be a n issue of concern.