Thermoelectric figure of merit of (In0.53Ga0.47As)0.8(In0.52Al0.48As)0.2 III-V semiconductor alloys

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 (In0.53Ga0.47As)(0.8)(In0.52Al0.48As)(0.2) of 2 mu 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 1.9 x 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 1.5 x 10(18) cm(-3).