纤锌矿ZnO/Zn_(1-x)Mg_xO非对称双量子阱中电子的带间跃迁光吸收

Light Absorption of Electron Interband Transition in Wurtzite ZnO/Zn_(1-x)Mg_xO Asymmetric Double Quantum Wells

考虑纤锌矿ZnO/Zn_(1-x)Mg_xO非对称双量子阱中内建电场的作用,运用有限差分法自洽求解导带(价带)薛定谔方程和泊松方程,得到系统中电子(空穴)的能级和波函数,进一步采用黄金费米法则求得电子带间跃迁的线性和非线性光吸收系数及折射率变化.结果显示,由于ZnO/Zn_(1-x)Mg_xO双量子阱中MV/cm量级的强内建电场,系统对尺寸和组分的调节作用较为敏感.当左阱宽度较小和中间垒达到一定宽度时,双阱的耦合作用增强;在给定阱垒宽度时,势垒的内建电场均随Mg组分的增加而增加,导致导带电子和价带空穴能级差变大且电子与空穴的空间分离,吸收峰及折射率变化峰值发生蓝移且相应峰值减小;随着中间垒宽度增加,相应峰值减小且发生红移;随着右阱宽度的增大,相应峰值先增后减且发生红移.此外,入射光强度可调节光吸收系数及折射率变化,随着光强的增加,光吸收系数及折射率变化峰值减小.

Considering the effects of the built-in electric field（BEF）in wurtzite ZnO/Zn（1-x）MgxO asymmetric double quantum wells（ADQWs）,and using the finite difference method to solve selfconsistently the Schrodinger equation and Poisson equation,the energy levels and corresponding wave functions of electrons（holes）are obtained in the conduction band（valence band）.Furthermore,using gold Fermi rule the linear and nonlinear optical absorption coefficients（OACs）and refractive index changes（RICs）are derived.The results show that the system is sensitive to the change of sizes and components due to the strong BEF up to MV/cm.When the width of left well is smaller and the width of center barrier is larger,the coupling effect of the double wells is strengthened;for given thicknesses of wells and barriers,the BEFs in the barriers increase with the increase of the Mg components,and lead to the differences between energy levels of electrons in the conduction band and holes in the valence band being large,a space separation between electrons and holes,OACs peak and RICs present blue shifts and their peaks decrease;with the increase of center barrier width,the corresponding peaks decrease and present red shifts;with the increase of right well width,the corresponding peaks firstly increase then decrease and present red shifts.In addition,the incident optical intensity（IOI）can modulate OACs and RICs.As increase of IOI,both peaks of OACs and RICs decrease.