Thermoelectric figure of merit of(In0.53Ga0.47As)0.8<

Abstract

The thermoelectric figure of merit is measured and theoretically analyzed for n-type Si-doped InGaAlAs III-V quaternary alloys at high temperatures. The Seebeck coefficient, electrical conductivity, and thermal conductivity of a Si-doped ͑In 0.53 Ga 0.47 As͒ 0.8 ͑In 0.52 Al 0.48 As͒ 0.2 of 2 m thickness lattice matched to InP substrate grown by molecular-beam epitaxy are measured up to 800 K. The measurement results are analyzed using the Boltzmann transport theory based on the relaxation-time approximation and the theoretical calculation is extended to find optimal carrier densities that maximize the figure of merit at various temperatures. The figure of merit of 0.9 at 800 K is measured at a doping level of 1.9ϫ 10 18 cm −3 and the theoretical prediction shows that the figure of merit can reach 1.3 at 1000 K at a doping level of 1.5ϫ 10 18 cm −3 .

The impact of commonly used approximations on the computation of the Seebeck coefficient and mobility of polar semiconductors

“…This may in part explain the apparent agreement with experiment obtained by Ref. 22 despite using the RTA combined with the truncated BTE for computing the Seebeck coefficient of a polar semiconductor with a low effective mass (0.048m 0 ).…”

“…Sometimes in the literature, 22 the starting point for transport calculations is not the full BTE, Eq. (1), but instead the truncated (or linearized) form derived by ignoring f 2 ðk; rÞ terms therein.…”

“…1,[19][20][21][22] It consists of entirely neglecting the term 1=C inelas ðk 0 ; k; zÞ in Eq. (2), and is strictly valid only if all scattering mechanisms are elastic, or if any inelastic mechanisms that may be present are isotropic.…”

Thermoelectric properties of In-rich InGaN and InN/InGaN superlattices

“…The difference between the values in the in-plane and cross-plane directions should be relatively small, since the film is sufficiently thick and that it is common to approximate κ in thin-film thermoelectrics from the values in the cross-plane direction. 7,11,13,19 Furthermore, the observation of significantly reduced κ by alloying without deterioration of electrical properties is one of the key benefits of alloyed materials for thermoelectrics. 7,17,22 The thermoelectric power factor (S 2 σ), which combines electrical conductivity and Seebeck coefficient, is further plotted in Fig.…”

“…Clearly, while the thermoelectric prospects for binary group-III-nitrides are rather poor due to their very high thermal conductivities (> 90 W/m-K), 17 ternary nitride alloys exhibit much improved thermoelectric properties [10][11][12][13][14][15] since alloying significantly reduces thermal conductivity. 18,19 Further progress has been, however, hampered largely by the unfavorable coupling between the quantities σ and κ as well as S and σ in bulk materials. Critically, the electrical conductivity and the electronic part of the thermal conductivity are coupled by the Wiedemann-Franz law, 20 while the Seebeck coefficient depends on carrier concentration and is, hence, inversely proportional to the electrical conductivity.…”