Determination of the B4-B1 phase boundary in semiconductors using isothermal compression Raman spectroscopy

Abstract

The pressure-induced phase transition from hexagonal wurtzite (B4) to cubic rock salt (B1) in semiconductors is generally identified as an important displacement-type structural transition. Despite the important advancements shown in the literature, the B4–B1 transition boundaries have yet to be well determined due to the experiment's technical challenges, especially in the low-temperature region, resulting in a blank in the pressure–temperature (P–T) phase diagrams and in the absence of experimental data on the Clapeyron slopes. Here, we probe the pressure-induced B4–B1 phase transition of some typical semiconductors (ZnO, GaN, AlN, and LiGaO2) at low temperatures (90–300 K) using a self-designed isothermal compression in situ Raman spectroscopy technique. We experimentally determine their B4–B1 phase boundaries at low temperature and obtain the corresponding negative Clapeyron slope parameters, with steeper slopes corresponding to larger entropy changes. Our findings provide insight into the pressure-induced B4–B1 transition in semiconductors and reveal the relationship between the bond energy and the Clapeyron slope in the B4–B1 transition.