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

1. p型ZnSe/BeMnTe量子阱结构的制备采用分子束外延方法在GaAs衬底上生长了ZnSe/N掺杂BeMnTe量子威尔斯阱和N掺杂BeMnTe薄膜。在<18><19><-3>2 ~ 300 K的温度范围内，获得了10^-10 ^cm-2的空穴载流子密度，这相当于载流子感生铁磁性所需的载流子密度。ZnSe/BeTe量子阱界面的截面结构分析载流子寿命和电子、空穴波函数的重叠强烈地依赖于界面质量，因为电子和空穴之间的复合发生在具有II型能带排列的量子威尔斯的界面处。我们研究的锐度和合金效应在多量子威尔斯层的ZnSe和BeTe层之间的界面处使用截面扫描隧道显微镜和X射线衍射测量。填充态和空态图像显示Zn-Te和Be-Se键 ...更多信息 在ZnSe/BeTe界面上沿生长方向沿着分布2-4个单层。ZnSe层和BeTe层之间的过渡层由对应于（ZnTe）_（BeSe）_的BeZnSeTe四元合金组成<0.58><0.42>。我们测量了掺N的Be_<1-x>Mn_xTe（x=0.05和0.10）样品的霍耳效应，发现Be_<1-x>Mn_xTe在低于10 K的温度下是铁磁的。首次观察到Be_ Mn_xTe的负磁电阻及其磁滞现象<1-x>，证实了其载流子感生铁磁性。高磁场下霍尔效应的观察支持了所观察到的负磁阻是由于外加磁场从束缚磁极化子中产生自由载流子的结果. ZnSe/BeMnTe量子阱结构的发光特性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发光有增强和减弱的作用。然而，我们不能观察到一个尖锐的发光带在高N掺杂的ZnSe/BeMnTe量子阱，因为在异质结的界面粗糙度。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