缓冲层对量子阱二能级系统中电子子带间跃迁光吸收的影响

由于ZnO缓冲层对纤锌矿ZnO/Mg_xZn_(1-x)O有限深单量子阱结构左垒的限制作用,导致阱和右垒的尺寸、Mg组分值等因素将影响系统中形成二能级.本文考虑内建电场、导带弯曲及材料掺杂对实际异质结势的影响,利用有限差分法数值求解Schr?dinger方程,获得电子的本征能级和波函数,探讨ZnO缓冲层对此类量子阱形成二能级系统的尺寸效应及三元混晶效应的影响;利用费米黄金法则探讨缓冲层、左垒、阱及右垒宽度和三元混晶效应对此类量子阱电子子带间跃迁光吸收的影响.计算结果显示:对于加入ZnO缓冲层的ZnO/Mg_xZn_(1-x)O有限深单量子阱二能级系统,左垒宽度临界值会随着阱宽和Mg组分值的增大而逐渐减小,随着右垒宽度和缓冲层厚度的增大而逐渐增大;量子阱中电子子带间跃迁光吸收峰会随着左垒、右垒尺寸以及Mg组分的增大发生蓝移,随着阱宽增大而发生红移.本文所得结果可为改善异质结器件的光电性能提供理论指导.

Buffer layer influence on light absorption of electron intersubband transition in binary energy level systems of quantum wells

Due to the restriction of the ZnO buffer layer on the left barrier in a wurtzite asymmetric ZnO/Mg_xZn_1-xO single quantum well (QWs) structure with finite barriers, the other factors such as the size of the well and right barrier, and Mg component, etc. will influence the critical value of the left barrier width to form a binary level energy system. By adopting a finite difference method to solve the Schrödinger equation, the eigenstates and eigenenergies of electrons in a two-dimensional electron gas are obtained, and the influences of buffer layer ZnO, size and ternary mixed crystal effects on the formation of binary energy level system in QW are discussed. In our computation, the influences of energy band bending, material doping and built-in electric fields on a realistic heterostructure potential are considered. Furthermore, based on the Fermi's golden rule, the optical absorption coefficient of electronic intersubband transition in QW and the influences of buffer layer thickness, the widths of left barrier, well and right barrier and ternary mixed crystal effects are discussed. Our results indicate that the critical width of left barrier increases with the increases of the right barrier width and buffer layer thickness for a binary energy level system of ZnO/Mg_xZn_1-xO single quantum well with a ZnO buffer layer on the left side. However, the critical width of left barrier decreases with the increase of well width and Mg component. Besides, the buffer layer thickness, the widths of left barrier, well and right barrier and ternary mixed crystal also affect the light absorption induced by the electronic intersubband transitions. The increases of Mg component, the widths of right barrier and left barrier will increase the absorption peak and produce its blue-shift. Whereas, increasing well width will reduce the absorption peak and produce its red-shift. The above conclusions are expected to give theoretical guidance in improving the opto-electronic properties of materials and devices made of these heterostructures.