调制n型掺杂ZnSe/BeTe Ⅱ型量子阱结构的发光特性

Optical property of modulated n-doped ZnSe/BeTe type-Ⅱ quantum wells

报道了调制n型掺杂ZnSe/BeTe/ZnSe Ⅱ型量子阱(type-IIQW)在极低温至室温(1.4—296K)条件下的各种光学性质.反射光谱显示了对于非掺杂样品,激子(X)的跃迁起着支配作用,而只有在掺杂样品的光谱里展示了一个典型的负的带电激子(X-)的跃迁特征.PL光谱及其直线偏振度Pl都显著地依赖于n型掺杂量和平行于QW生长方向的外加电场.这个特征被认为是由n型掺杂导致了内秉电场(built-inelectric field)消失及外加电场引起斯塔克效应(Stark effects)所致.还用外加电场方法证明了内秉电场的存在.超强磁场(高达180T)下的回旋共振(CR)测量证实了掺杂样品中确实存在着较高浓度的二维电子气,并且这些电子受限于ZnSe阱层中.以上实验结果显示在掺杂样品中同时观察到了Ⅰ型(空间直接)跃迁和Ⅱ型(空间间接)跃迁中的带电激子特征,同时也显示了所用样品达到了预期的设计目的.

We report the optical properties of the modulated n-doped ZnSe/BeTe/ZnSe type-Ⅱ quantum wells. The reflection spectra have shown typical negatively charged exciton features only in a doped sample. The luminescence spectra and the polarization anisotropy depend strikingly on both the n-doping into the barrier layers and an applied external electric field perpendicular to the layer. These are explained by screening of the built-in electric field with n-doping and Stark effects due to the applied electric field. The electron density as well as the mass was determined in high magnetic field （up to 160 T） cyclotron-resonance measurements. It was found that the observed indirect PL transition occurs via the charged excitons in a type-Ⅱ quantum configuration.