Investigation of conduction band structure, electron scattering mechanisms and phase transitions in indium selenide by means of transport measurements under pressure

TL;DR

This study investigates how pressure affects the electronic structure, scattering mechanisms, and phase transitions in indium selenide through transport measurements, revealing pressure-induced band shifts, electron trapping, and a phase change.

Contribution

It provides new insights into pressure-dependent conduction band behavior, electron trapping, and phase transition mechanisms in indium selenide, combining experimental data with analysis of electronic and structural changes.

Findings

Carrier concentration decreases with pressure due to a subsidiary conduction band minimum.

Electron mobility increases under pressure, more so for 2D electrons.

A phase transition from semiconductor to metallic phase occurs around 105 kbar.

Abstract

In this work we report on Hall effect, resistivity and thermopower measurements in n-type indium selenide at room temperature under either hydrostatic and quasi-hydrostatic pressure. Up to 40 kbar (= 4 GPa), the decrease of carrier concentration as the pressure increases is explained through the existence of a subsidiary minimum in the conduction band. This minimum shifts towards lower energies under pressure, with a pressure coefficient of about -105 meV/GPa, and its related impurity level traps electrons as it reaches the band gap and approaches the Fermi level. The pressure value at which the electron trapping starts is shown to depend on the electron concentration at ambient pressure and the dimensionality of the electron gas. At low pressures the electron mobility increases under pressure for both 3D and 2D electrons, the increase rate being higher for 2D electrons, which is shown to be coherent with previous scattering mechanisms models. The phase transition from the semiconductor layered phase to the metallic sodium cloride phase is observed as a drop in resistivity around 105 kbar, but above 40 kbar a sharp nonreversible increase of the carrier concentration is observed, which is attributed to the formation of donor defects as precursors of the phase transition.