Under Biaxial Strain Algan/gan Two-dimensional Electron Gas Migration Rate Calculation

With the increasing need for high-frequency, high-power, and high-temperature microwave applications in a variety of military and commercial wireless communications applications, AlGaN/GaN high electron mobility transistors (HEMTs) have generated a considerable amount of research activity due to their superior material features such as high breakdown field, high electron saturation velocity, and high operating temperature. The mobility of electrons in the two-dimensional electron gas (2DEG) at the GaN side of the AlGaN/GaN interface is an important transport parameter used to characterize the performance of HEMTs’ structures. Moreover, strain engineering as a new method of enhancing charge transport properties plays a critical role in modern device technologies. Therefore, it is of significance to study the influence of strain on mobility to improve the performance of HEMT. In this paper, the mobility of2DEG in AlGaN/GaN under biaxial strain was studied. Main conclusions are listed below.First, materials studio (MS) software is used to calculate the relevant physical parameters of GaN under biaxial strain. At the same time, a discusstion is carried out about their effects on single scattering mechanism mobility and total mobility in detail.(1) The polarized optical phonon energy has the greatest impact on the2DEG mobility at room temperature.2DEG mobility increases monotonically as the phonon energy. In the case of the other parameters fixed, the rate of change of the mobility is three times as big as that of the phonon energy.(2) The relationship between the high frequency dielectric constant(ε∞) and the biaxial strain is approximately a parabola. With the biaxial strain, the high frequency dielectric constant increases gradually. However, the relationship between the low frequency dielectric constant(ε0) and the biaxial strain is linear. The mobility increases with the low frequency dielectric constant at300K while decreases at77K. The effect of the dielectric constant on the total mobility is small.(3) The elastic constant decreases with the tensile strain and increases with the compressive strain. With the range of2%strain, the longitudinal elastic constant and the transverse elastic constant changes by about10%and25%, respectively. Despite this, the contribution of the elastic constants to mobility is very small, changing less than0.5%.Next, the calculated physical parameters is used to calculate the mobility under strain in the light of electron scattering mechanisms in AlGaN/GaN heterostructure.(4) At300K, the trend of the total mobility under strain is consistent with the polarized optical phonon scattering or the alloys disorder cattering when the2DEG concentration is beyond4×1013cm-2. At the low temperature77K, the mobility does not depend on the strain at the low concentration. However, the trend agrees with alloys disorder cattering, which become the main scattering mechanism as the concentration increasing.(5) In the case of a fixed concentration, the low-temperature mobility increases with the tensile strain or decreases with the compressive strain; when the temperature increases up to about150K, this relationship begins to be reversed.(6) The electric field of2×108N/C imposed on the lead zirconate titanate (Zr/Ti=52/48) can produce the same effect with2%strain. That what we imposed is the tensile strain or the compressive strain can be determined by the adjustment of the direction of the elelctric field. Thus, the mobility can be modulated by strain.