Three dimensional superlattice in Pb1−χGdχTe (Wigner's crystallization)

A diluted magnetic semiconductor (DMS) containing a rare earth, Pb1−χGdχTe, has been synthesized using the Bridgman technique. The nominal gadolinium concentration was adjusted to be between 1 to 5%. Both n and p-type crystals were grown by synthesizing lead or tellurium rich ingots. Single crystal samples oriented in the (111) direction were used for electrical characterizations. Electron and hole mobilities as high as 1 × 107 cm2V-1s-1 and 2.5 × 105 cm2V-1s-1 measured at 4.2K. Both types of mobilities as a function of temperature exhibit the typical T-32 law, which is characteristic of semiconductors. Wigner's crystallization is invoked to elucidate the possible existence of an ionized impurity formed three dimensional superlattice to account for these high charge carrier mobilities.