External Electric Field Effect on Shallow Donor Impurity States in Zinc-Blende InxGa1−xN/GaN Symmetric Coupled Quantum Dots

Guang-Xin Wang,Huan Wei,Li-Li Zhang

doi:10.1155/2017/5652763

Abstract

Based on the effective-mass approximation and variational procedure, the ground-state donor binding energy in a cylindrical zinc-blende InxGa1-xN/GaN symmetric coupled quantum dots (SCQDs) is investigated in the presence of the external electric field. Numerical results show that the donor binding energy increases firstly until a maximum value, and then it begins to drop quickly in all the cases with decreasing the dot radius. As the thickness of left dot and right dot decreases, the donor binding energy increases monotonically at first, reaches a maximum value, and then drops rapidly for an impurity ion located at the right dot center and the middle barrier center. Moreover, the donor binding energy for an impurity ion located at the center of the left dot is insensitive to the variation of dot thickness for large dot thickness due to the Stark effect. Meanwhile, the impurity position plays an important role on the change of the donor binding energy under the external electric field. In particular, the impurity position corresponding to the peak value of the donor binding energy is shifted toward the left QD with increasing the external electric field strength.

Highlights

Recent advances in modern fabrication techniques have made it possible to grow wide-band-gap GaN-based lowdimensional semiconductor quantum structures [1, 2] and InxGa1−xN ternary alloys, as one of the most important members of the group III nitride semiconductor family such as quantum wells (QWs), quantum well wires (QWWs), and quantum dots (QDs), and have attached considerable attention due to their unique electronic and optical properties, as well as their potential applications in electronics and optoelectronic devices [3, 4]
Number results can be summarized as follows: (1) as the QD radius increases, the donor binding energy increases firstly until a maximum value, and it begins to drop quickly in all the cases; (2) as the dot thickness L decreases, the donor binding energy increases monotonically at first, reaches a maximum value, and drops rapidly for the impurity located at right dot center and middle barrier center
The donor binding energy is insensitive to the variation of dot thickness for large dot thickness when the impurity ion is located at the left dot center

Summary

Introduction

Recent advances in modern fabrication techniques have made it possible to grow wide-band-gap GaN-based lowdimensional semiconductor quantum structures [1, 2] and InxGa1−xN ternary alloys, as one of the most important members of the group III nitride semiconductor family such as quantum wells (QWs), quantum well wires (QWWs), and quantum dots (QDs), and have attached considerable attention due to their unique electronic and optical properties, as well as their potential applications in electronics and optoelectronic devices [3, 4]. Xia et al studied the hydrogenic impurity states in ZB InGaN single QD in the absence of the applied electric field (GaN/AlN coupled QDs) [15, 16]. We investigated the combined effects of an intense laser field, electric field, and hydrostatic pressure on donor impurity states in zincblende InGaN/GaN quantum dots [19]. It is necessary to study the external electric field effect of the donor impurity states in ZB GaN-based coupled QDs. In this paper, using effective-mass approximation and variational procedure, we report the calculation of ground-state donor binding energy in coupled QDs in the presence of an electric field along the growth direction of the SCQDs. The effects of the structure parameters of the SCQDs, the impurity position, and the applied electric field are all taken into account.

Theoretical Framework

Results and Discussion

Conclusion