Impurity doping of HgTe–CdTe superlattices during growth by molecular-beam epitaxy

Abstract

We demonstrate the use of In and Ag as n- and p-type dopants, respectively, to controllably dope (100)-oriented HgTe–CdTe superlattices during molecular-beam epitaxial (MBE) growth. When normalized by the superlattice growth rate, the low-temperature Hall-carrier concentrations of both In- and Ag-doped superlattices are shown to have an exponential dependence on the respective effusion-cell temperatures in the electron and hole concentration ranges of ∼1016 to 1018 cm−3 . The upper limit on the diffusion coefficient for In at the low MBE growth temperature of ∼160 °C is determined to be 5×10−15 cm2 /s by use of secondary-ion mass spectrometry. Hall-effect and current–voltage measurements verify that the combination of In and Ag doping allows the formation of p–n electrical junctions. These results provide the first evidence of p–n junction formation in a HgTe–CdTe superlattice.