Lead–rare‐earth chalcogenides grown by molecular beam epitaxy

The development of wide band gap alloys of lead–telluride (PbTe) would extend the total wavelength range covered by lead–tin–telluride (Pb1−xSnxTe) diode lasers. The advantages of alloys of PbTe with ytterbium (Yb) or europium (Eu) over those of cadmium, manganese, and germanium grown by molecular beam epitaxy (MBE) are discussed. Experimentally, it was found that Yb atoms bond strongly to a PbTe surface and have a small diffusion coefficient (<3×10−17 cm2/s at 370 °C). The lattice constant (in A) of Pb1−xYbxTe is 6.460–0.015 x for 0≤x≤0.42. Yb introduces a donor level into PbTe near the valence band edge which is caused by the Yb+2=Yb+3+e− transition. The level appears to move into the valence band in (Pb0.85Sn0.15)1−xYbxTe for x≲0.07, making it possible to dope the material p‐type as well as n‐type for diode laser applications.