Electron transport in two dimensional electron gas formed at the heterojunction of AlxGa(1-x)N/GaN at microwave frequencies
Abstract Transport properties of the two dimensional electron gas (2DEG) formed at the interface of AlGaN/GaN heterostructure ranging from 20 K to 300 K has been investigated theoretically considering the various scattering mechanisms like the acoustic, the piezo, the surface roughness, the alloy, the polar optical phonon and the dislocation scattering. The dc mobility is found to remain constant up to 150 K and then it decrease sharply with further increase in temperature. The ac mobility is also found to decrease with increase in the temperature. The real part of ac mobility, i.e. μr decreases with the increase in the frequency very fast initially and then gradually attains a steady value. The imaginary part of the ac mobility μim initially increases with the increase in the frequency and then decreases after reaching the maximum value. The value of the ac mobility reduces quite reasonably as the 2D carrier concentration increases at lower range of the frequency. At the carrier concentration of 5 × 1017 m−2, the ac mobility remains constant through a wide range of frequencies. With the increase in the dislocation densities, the values of the ac mobility are found to decrease at the lower range of frequencies. The thermo electric power is positive at the 2D carrier concentration of 5 × 1016 m−2, the value of which increases with the increase in the temperature and gradually attains a steady value. But the thermoelectric power at n2D of 1017 m−2 is found to be negative in the value. The value of ZT is found to increase with the temperature and attains the maximum value of 0.007 at 150 K and the value of ZT then decreases with increase in the temperature.