Study on photo-induced magnetic transition in II-VI diluted magnetic semiconductor quantum wells with a type band allignment

1.p型ZnSe/BeMnTe量子井结构的制备采用分子束外延方法在GaAs衬底上生长了掺N的BeMnTe和掺N的HBMnTe薄膜。在2~300K.2的温度范围内，获得了空穴载流子密度为10^-lt；18-10^-lt；19-gt；cm^-lt；-3-gt；对应于载流子感生亚铁磁性所需的载流子密度。载流子寿命和电子和空穴波函数的重叠强烈依赖于界面质量，因为电子和空穴之间的复合发生在量子阱中具有第二类能带排列的界面上。我们用横截面扫描隧道显微镜和X射线衍射仪研究了多量子阱中锌硒和贝特层界面的锐度和合金效应。填充态和空态图像揭示了锌-碲和铍-硒…在沿生长方向的2-4个单分子层范围内，在ZnSe/Bete界面上存在较多的DS。在ZnSe层和Bete层之间的过渡层由对应于(ZnTe)_&lt；0.58&gt；(Bese)_&lt；0.42&gt；的BeZnSeTe四元合金组成。反常霍尔效应和铁磁跃迁的观察我们测量了N掺杂Be_t；1-x&Gt；Mn_xTe(x=0.05和0.10)的反常霍尔效应，发现Be_&lt；1-x&Gt；Mn_xTe在低于10K的温度下是铁磁的，首次观察到了Be_&lt；1-x&Gt；Mn_xTe的负磁电阻及其磁滞回行为，证实了载流子诱导的铁磁性。在高磁场下观察到的霍尔效应支持了观察到的负磁电阻是由于外加磁场作用下束缚磁极化子产生自由载流子所致。研究了外加电场和磁场对发光特性的影响，发现外加电场对界面处的发光有增强作用，也有抑制作用。然而，由于异质结界面的粗糙，我们在高N掺杂的ZnSe/BeMnTe量子阱中没有观察到明显的发光带。较少

1. Preparation of p-type ZnSe/BeMnTe quantum well structuresZnSe/N-doped BeMnTe quantum wells and N-doped BeMnTe thin films were grown on GaAs substrates by a molecular beam epitaxy method. The hole carrier density in the range of 10^<18>-10^<19> cm^<-3>, which corresponds to the carrier density necessary for carrier-induced ferrpmagnetism, was obtained at the temperatures between 2 and 300 K.2. Analysis of cross-sectional structure of ZnSe/BeTe quantum well interfacesCarrier lifetimes and overlapping of electron and hole wave functions strongly depend on the interfacial quality, because the recombination between electrons and holes takes place at the interfaces in the quantum wells with a type II band alignment. We investigated sharpness and alloy effects at the interfaces between ZnSe and BeTe layers in the multiple quantum wells using cross-sectional scanning tunneling microscopy and X-ray diffraction measurements. The filled- and empty-state images revealed that Zn-Te and Be-Se bon … More ds exist at the ZnSe/BeTe interface within the range of 2-4 monolayers along the growth direction. The transition layer between the ZnSe layer and the BeTe layer is composed of the BeZnSeTe quaternary alloy corresponding to (ZnTe)_<0.58>(BeSe)_<0.42>.3. Observation of anomalus Hall effects and ferromagnetic transitionWe measured anomalus Hall effects in N-doped Be_<1-x>Mn_xTe (x=0.05 and 0.10), and found that Be_<1-x>Mn_xTe is ferromagentic at the temperature lower than 10 K. Negative magnetoresistance and its hysterisis behavior were observed for the first time for Be_<1-x>Mn_xTe, which confirmed the carrierd-induced ferromagnetism. The observation of the Hall effect with the high magnetic field supported that the observed negative magnetoresistance is due to free carrier generation from bound magnetic polarons by the applied magnetic field.4. Luminescence properties of ZnSe/BeMnTe quatum well structuresWe investigated effects of applied electric and magnetic fields on luminescence properties, and found that the luminescence at the interfaces is enhanced and reduced by the applied-electric field. However, we could not observe a sharp luminescence band in the highly N-doped ZnSe/BeMnTe quantum well because of the interfacial roughness at the heterojunctions. Less