Thermoelectric studies of electronic properties of ferromagnetic GaMnAs layers

TL;DR

This study investigates the thermoelectric and electronic properties of ferromagnetic GaMnAs layers, revealing insights into carrier transport mechanisms, Fermi energy, and the effects of temperature and conductivity type.

Contribution

It provides new analysis of thermoelectric power in GaMnAs layers, determining Fermi energy and carrier concentration across different conductivity regimes.

Findings

Fermi energy approximately 220 meV, nearly independent of Mn content.

Metallic layers show thermoelectric power maximum near Curie temperature.

Insulating layers exhibit 1/T increase in thermoelectric power at low temperatures.

Abstract

Thermoelectric power, electrical conductivity, and high field Hall effect were studied over a broad temperature range in ferromagnetic Ga(1-x)Mn(x)As epitaxial layers (0.015<x<0.06). Thermoelectric power analysis gives the information about carrier transport mechanisms in layers with both metallic and non-metallic type of conductivity and allows determination of the Fermi energy and carrier concentration. At high temperatures (T>70 K) the thermoelectric power in GaMnAs linearly increases with increasing temperature. That indicates the presence of a degenerate hole gas with the Fermi energy EF=220+-25 meV, nearly independent of Mn content (for 0.02<x<0.05). At lower temperatures GaMnAs layers with metallic-type conductivity show an additional contribution to the thermoelectric power with the maximum close to the Curie temperature. The layers exhibiting insulating electrical properties show 1/T-type increase of thermoelectric power at low temperatures.