QUANTITATIVE INVESTIGATION OF INTERDIFFUSION EFFECTS IN BALANCED-STRAIN INGAAS(P) INGAASP HETEROSTRUCTURES - CONSTANT-X VS CONSTANT-Y/

We report a comparative investigation of the effect of intermixing per formed on three different series of separate confinement heterostructu res grown for 1.55 mu laser applications. All were strain compensated multi-quantum well (MQW) stacks but were grown using different design options. In the first case, the MQW was grown using the same nominal c oncentration of cationic species in the wells and the barriers. This c orresponds to the so-called ''constant x'' design. In the two other ca ses, the concentration of anions was kept constant. This is the ''cons tant y'' design. In this case, to determine any effect of substrate et ch-pit density (EPD), two different samples were gown. Previous invest igations indicate superior thermal stability of structures with a ''co nstant y'' design, and assign this effect to the lower diffusivity of cations in III-V heterostructures. In this work, we found the followin g. (i) there is only a 30% difference in diffusivity between the two s ystems; (ii) within experimental uncertainty there is little dependenc e on the wafer EPD; (iii) in the particular case of our sample geometr y, the superior thermal stability of the constant y design is due to t he difference in device geometry and not kinetic effects.