Growth of lead‐germanium‐telluride thin film structures by molecular beam epitaxy

The development of Pb1−xGexTe devices would extend the total wavelength range that can be covered by tunable diode lasers. Pb1−xGexTe was grown from PbTe, GeTe, and Te sources at 2 μm/h and in vacuums <10−8 Torr. The Ge concentration as a function of depth in the grown layers was measured with Auger electron spectroscopy in combination with argon ion sputtering. GeTe segregates on the surface for substrate growth temperatures of 220 °C and below, and preferentially evaporates at 330 °C. Heat treatment of PbTe/Pb1−xGexTe superlattice structures with 200 A periodicity yields a Ge diffusion coefficient of 2×10−18 cm2/s at 270 °C. The effect of lattice mismatch on crystal quality was determined from etch pit density studies. PbTe/ Pb1−xGexTe/PbTe structures with thin intermediate layers had much lower etch pit densities than thicker films, in good agreement with theory.