调制掺杂ZnSe/BeTe Ⅱ型量子阱结构中的内秉电场和新型带电激子

Built-in electric field and a new type of charged excitons observed in modulation-doped ZnSe/BeTe type-Ⅱ quantum well

报道了调制掺杂的ZnSe/BeTe/ZnSeⅡ型量子阱(type-ⅡQW)在低温(2—5K)条件下的光致发光(PL),光致发光激发(PLE)和磁性光致发光(magneto-PL)光谱的实验结果.观察到非掺杂样品的PL有两个很强的主发光峰而掺杂样品只有一个的奇异发光.PL直线偏振度和PLE的测量结果都表明了这些空间间接型跃迁PL是来自两个异质结界面的贡献,非掺杂样品的两个主发光峰的分离则是起因于QW结构中的内秉电场(built-in electric field).在平行于QW生长方向的强磁场中,掺杂样品的发光强度和主发光峰能量都显示了一个光学Shubinkov-de Hass(SdH)振荡.这些特征及另外的吸收光谱测量结果都表明,在掺杂样品中已经形成了一个高浓度的二维电子气;它具有type-ⅡQW所特有的带电激子的特征.

We report results of the photoluminescence, photoluminescence excitation, and magneto-photoluminescence spectra measurements performed on modulation doped ZnSe/BeTe/ZnSe type-Ⅱ quantum well structures at low temperature （2-5 K）. The non-doped sample showed two distinct peaks, while the doped one showed one peak only. The linear polarization degree measured in both photoluminescence and the photoluminescence excitation spectroscopy indicates that photoluminescence transitions of an indirect type takes place at respective heterointerfaces. The peak splitting in the non-doped sample was caused by a built-in electric field resulting from the spatial separation of charges along the growth axis. We found optical Shubinkov-de Hass oscillations in both the photoluminescence intensity and the transition energy under a high magnetic field perpendicular to the well. These features and the additional absorption （or reflection） spectra measurements demonstrated that two-dimensional electron gas of a high concentration was formed in the doped samples. All these present the signature of charged excitons and also of a correlated excitonic phase of type- Ⅱ quantum wells.