Thermodynamic properties of metastable wurtzite InP nanosheets

Low-dimensional III–V semiconductor arrays have been widely investigated for photonic, electronic and optoelectronic applications. Bottom-up epitaxy of nanostructures with metastable phase is an effective approach to modify their optical and electronic structures. However, in addition to their optical properties, their thermal properties are also important and can affect device performance. Here, we use wurtzite InP nanosheet arrays as an example and perform detailed optical and Raman scattering studies. It is shown that Al₂O₃ provides good protection for nanosheets up to 873 K without any observable deterioration in optical properties or phase transition. The A₁(TO) and E_2h modes show opposite trends in polarization-dependent Raman scattering. The first-order temperature coefficient and thermal expansion coefficient of wurtzite and zincblende InP are obtained from temperature-dependent Raman experiments and are quite close to each other. Furthermore, by applying density functional theory and density functional perturbation theory, the Grüneisen parameter and the thermal expansion of wurtzite InP lattice are calculated, showing good agreement with the experimental Raman data. There is little thermodynamic property difference between wurtzite and zincblende InP phase. The revealed thermal properties of the InP nanosheets provide valuable information for those devices that operate at high temperatures.