High-pressure X-ray diffraction study of InAs

Abstract

Structural phase transitions in III–V semiconductors have been the subject of numerous experimental and theoretical studies. Contrary to traditional expectations, recent high-pressure X-ray experiments showed that the NaCl (Fm3m) structure is not present in the more covalent systems, and the diatomic β-tin (I-4m2) structure is absent in the more ionic semiconductors. Theoretical studies explained these systematic absences in terms of dynamical phonon instabilities of these structures. At higher pressures these calculations showed that the traditionally expected CsCl (Pm3m) phase is unstable for the more ionic III–V compounds, and proposed two alternative structures: P4/nmm and Pmma. We studied the III–V semiconductor compound InAs under pressure in a diamond anvil cell by angle-dispersive X-ray diffraction using two different pressure transmitting media (PTM) (silicone oil and nitrogen). The data, analyzed by Rietveld method, show the following structural sequence: F-43m→Fm3m→Cmcm → “New phase of lower symmetry”. This sequence is preserved for the two PTM, although the pressure range in which there is coexistence of two different phases is reduced in the case of nitrogen as PTM. In the F-43m→Fm3m transition we observe a volume reduction of 18%, while there is no volume discontinuity associated to the following two transitions. Our results represent the first experimental evidence of the absence of the CsCl phase in these systems.