Te doping of GaInP: Ordering and step structure

The donor Te has been added to GaInP during organometallic vapor phase epitaxial growth using the precursor diethyltelluride. In agreement with previous studies, the addition of high Te concentrations leads to the elimination of the CuPt ordering observed in undoped layers. The degree of order is estimated from the low temperature photoluminescence peak energy to decrease from 0.5 at Te concentrations of <2×1017 cm−3 to 0 for Te concentrations of >6×1017 cm−3. This is verified by transmission electron diffraction studies, which show the elimination of the 1/2{111} superlattice spots at high Te doping levels. A remarkable change in the surface structure is found to accompany this decrease in ordering: The surfaces become much smoother. Step bunching is observed to disappear for the vicinal GaAs substrates, misoriented from (001) by 3° in the B direction, and three-dimensional island (or mound) formation is eliminated for the singular (001) substrates. A qualitative model is presented explaining this behavior based on the effect of Te on the step structure and the bonding at step edges, both of which affect the adatom sticking at steps.