Vibrational dynamics in semiconductor compounds and alloys

Abstract

In this work, the binary III-V semiconductors GaP, GaAs, GaSb, InP, InAs, und InSb, and the ternary alloys (In,Ga)P and (In,Ga)As were studied using temperature dependent extended x-ray absorption fine structure spectroscopy (EXAFS) measurements. In the alloy systems, the element-specific effective bond-stretching force constants were determined as a function of composition. To broaden the fundament of the conclusions, literature values of the ternary II-VI alloy Zn(Se,Te) were incorporated in the discussion. Different trends with composition are visible for (In,Ga)P on the one hand and (In,Ga)As and Zn(Se,Te) on the other hand. Strikingly, most of the six bond species under study (Ga-P, In-P, Ga-As, In-As, Zn-Se, and Zn-Te) exhibit the same relative change in bond-stretching force constant as a function of the relative change in bond length. Additionally, exactly the same relation is known from the literature as describing pressure-dependent EXAFS measurements of CdTe. The composition-dependent change of bond-stretching force constants in ternary zinc-blende semiconductor alloys is therefore caused mainly by the forced bond length change occurring in these materials. In addition to the bond-stretching force constants, effective bond-bending force constants were determined for the binary materials. Either type of force constants can be described as a function of ionicity and reduced mass of the interatomic bond. In the analysis great care has been taken to properly assess the uncertainties of the results. The comprehensive testing scenarios required to do this, also enable a general evaluation of the potential of the determination of bond force constants from temperature-dependent EXAFS measurements.