A variational method combined with solving the force balance equation is adopted to investigate the influence of strain and hydrostatic pressure on electronic mobility in a strained wurtzite AlN/GaN heterojunction by considering the scattering of optical-phonons in a temperature ranges from 250 to 600 K. The effects of conduction band bending and an interface barrier are also considered in our calculation. The results show that electronic mobility decreases with increasing hydrostatic pressure when the electronic density varies from 1.0 × 1012 to 6.5 × 1012 cm-2. The strain at the heterojunction interface also reduces the electronic mobility, whereas the pressure influence becomes weaker when strain is taken into account. The effect of strain and pressure becomes more obvious as temperature increases. The mobility first increases and then decreases significantly, whereas the strain and hydrostatic pressure reduce this trend as the electronic density increases at a given temperature (300 K). The results also indicate that scattering from half space phonon modes in the channel side plays a dominant role in mobility.
The screening effect of the random-phase-approximation on the states of shallow donor impurities in free strained wurtzite GaN/Al x Ga 1 x N heterojunctions under hydrostatic pressure and an external electric field is investigated by using a variational method and a simplified coherent potential approximation.The variations of Stark energy shift with electric field,impurity position,Al component and areal electron density are discussed.Our results show that the screening dramatically reduces both the blue and red shifts as well as the binding energies of impurity states.For a given impurity position,the change in binding energy is more sensitive to the increase in hydrostatic pressure in the presence of the screening effect than that in the absence of the screening effect.The weakening of the blue and red shifts,induced by the screening effect,strengthens gradually with the increase of electric field.Furthermore,the screening effect weakens the mixture crystal effect,thereby influencing the Stark effect.The screening effect strengthens the influence of energy band bending on binding energy due to the areal electron density.
