Comparative study of point defects induced in PbTe thin films doped with Ga by different techniques

The deviation from a stoichiometry and the amphoteric behaviour of Ga in PbTe/Si films

“…As it was reported in previous work [14], in PbTe/GaS films prepared by vapour phase doping the unit cell parameter have risen monotonically up to the value a PbTe ¼0.6464570.00006 nm with the increase in Ga concentration within the range of 0.001oy Ga o0.008. In other words, the influence of solid-state reactions, which may occur during vapour phase Ga-doping (the occupation of Pb vacancies V Pb by Ga atoms Ga Pb , the implantation of Ga atoms in tetrahedral voids Ga i , the formation of Te vacancies V Te , and ionisation of these point defects with electrons generation only) has enhanced the donor activity of Ga impurity atoms [14].…”

“…The second section of this dependence shows the increase in the unit cell parameter a PbTe within the concentration interval 0.0037oy Ga o 0.009-0.011. At further increase in Ga concentration the lattice parameter did not change [14]. These facts allow us to assume that non-monotonic character of a PbTe ¼f (y Ga ) curve as well as charge carrier densities evolution are connected with different position of Ga impurity atoms in PbTe crystal structure.…”

“…5. The lattice parameter a PbTe o Ga 4 evolution with impurity atoms concentration y Ga of Pb 1 À y Ga y Te 1 7 d films synthesised on Si-substrates by one-stage method[14]: 1-homogeneous samples; 2-heterogeneous samples.…”

Nature of gallium deep centres in lead telluride based semiconductors

“…We will consider the vapour phase doping with Ga 2 Te molecules, widely used in practice [20][21][22], and the hypothetical dop− ing with Ga 2 dimers or isolated gallium atoms for compari− son. In these cases, prefabricated bulk or thin film PbTe samples must be annealed in the corresponding envi− ronment.…”

“…Ga 2 dimer placed in the Pb site forms relatively strong ionic−covalence bonds with six Te atoms and in such a way, the overall doping process leads to energy lowering. In other terms reaction of the Ga 2 Te molecule with the bulk PbTe is the exothermic one (in practice thin PbTe films are used [20,21]). …”