Thermoelectric properties of and devices based on free-standing GaN

We have studied the thermoelectric properties of free-standing GaN and fabricated a themoelectric power device using this GaN. The electrical resistivity ρ increased and the Seebeck coefficient α slightly increased with increasing temperature in the range from 373 K to 973 K. The power factor decreased with increasing temperature, and its maximum value was 7.0 × 10 − 4 W ∕ mK 2 at 373 K. The device showed a maximum output voltage V op and an output power P max of 28 mV and 3.35 μ W at temperature difference of 153 K, respectively. The P max and V op were functions of the temperature difference ( Δ T ) , namely, P max ∼ ( Δ T ) n ( n = 2.14 ) and V op ∼ ( Δ T ) n ( n = 1.06 ) .