压力下GaN/Ga_(1-x)Al_xN量子点中杂质态的界面效应

Interface Effect on the Impurity State in a GaN/Ga_(1-x)Al_xN Quantum Dot under Pressure

考虑界面处导带弯曲,流体静压力以及有效质量随量子点位置的依赖性,采用变分法以及简化相干势近似,研究了无限高势垒GaN/Ga1-xAlxN球形量子点中杂质态的界面效应,计算了杂质态结合能随量子点尺寸、电子面密度以及压力的变化关系。结果表明,结合能随压力的增大呈线性增加的趋势,有效质量位置的依赖性以及导带弯曲对结合能有不容忽视的影响。

Semiconductor structures with quantum confinement have shown interesting behavior. In recent years, the physical properties of quantum heterostructures composed of the group-Ⅲ nitrides semiconductors with wide-band-gaps, such as A1N, GaN and InN, as well as their ternary compounds, have been widely studied arising from their promising application in short-wavelength electroluminescence devices. The high pressure, high electric-field, intense magnetic-field become the powerful tools to explore the property of material. Some authors investigated the effects of electric field and hydrostatic pressure on donor binding energies in a GaAs quantum dot. Some authors calculated the ground-state binding energies for a hydrogenic impurity in a spherical quantum dot within a uniform magnetic field. How ever, However, few studies focused interface effect and hydrostatic pressure on zinc-blende nitride quantum dots. As the periodicity of the host semiconduc- tor is lost, or when the impurity potential varies too rapidly over an effective Bohr radius the effective mass approximation is not reliable. In the present work, a modified variational method within the simplified coherent potential approximate was adopted to investigate the impurity state binding energies of GaN/Ga1-xAlxN infinite barrier spherical shape quantum dot by using a triangular potential to approximate the interface potential.Considering the hydrostatic pressure and a position dependent mass, the relations among the impurity binding energies, the hydrostatic pressure, quantum dot radius and the electron areal density were calculated. The re- sult indicated that the binding energies of impurity state nearly linearly increase with pressure. It also showed that the influence of conductive band bending and the position dependent effective mass should not be neglected. As the quantum dot radius is smaller, the binding energies are not affected by conductive band bending. With the increasing of the quantum dot size, the binding energies increase gradually with it. For a given hydrostatic pressure and Al component, the electron areal density ns strengthens the band bending of the interface to increase the binding energy.