Pressure-induced variation of effective dynamic charge in InP1−xAsx alloys due to charge transfer within cation sublattice

From the measurements of Raman spectra of ternary InP1−xAsx (x=0.4, 0.6, and 0.8) under high pressure, the pressure-dependence of the ionicity was found to be strongly affected by the As mole fraction x. In particular, for x=0.6 and 0.8 ternary alloys, the effective dynamic charge of InP-like mode strictly increases with pressure, in sharp contrast to the corresponding behavior satisfied by the majority of III–V and II–VI binary compounds including InP. This can be understood by the charge transfer from As to P in the cation sublattice when the ternary alloys are under pressure. ► Raman spectra of ternary InP1−xAsx films were measured under high pressure. ► Pressure causes the ionicity of the alloy change. ► The As mole fraction x affects the ionicity-change rate with pressure. ► For some x, the ionicity increases with pressure, in contrary to other compounds. ► Charge transfer from As to P in the cation sublattice is responsible for this behavior.