高掺杂Ga对ZnSe:Ga,Cu晶体中深中心发射的影响

本文研究了高掺杂Ga对ZnSe:Ga,Cu晶体中深中心光致发光谱带的影响。首次在高掺杂ZnSe:Ga,Cu中观察到了Cu-G带峰值位置随Ga浓度增大向长波方向移动的现象,并把它归因于高浓度的Ga和Cu相互作用,产生了谱峰为5580Å的新发射带,其半高宽(FWHM)大于Cu-G谱带的半高宽。此外还得到,随着Cu浓度增加,Cu-G带与Cu-R带强度之比减小。文中指出,Ga浓度较低时,ZnSe:Ga,Cu晶体与ZnSe:Cu晶体有相同的Cu深中心发射规律,即随着Cu浓度增大,Cu-G带与Cu-R带的强度比增大,由Cu-R发射带占优势逐渐过渡到Cu-G发射带占优势。     

真空中加热衬底对ZnSe MIS二极管电致发光的影响

本文研究了在制备ZnSe MIS二极管的绝缘层时,为了改善IS间的界面接触,在真空中加热ZnSe衬底,其结果虽然使电致发光的均匀性有所改善,却使原来的蓝色电致发光变为红色。文中着重研究了红色电致发光的起源,在液氮温度下出现的二个峰值为5350Å和6320Å的谱带应分别归结为ZnSe晶体中的铜绿(Cu-G)和铜红(Cu-R)发光中心。文中指出,真空中加热的条件,使ZnSe晶体中残留的Cu杂质从非发光中心状态转变为发光中心状态。因此,要改善ZnSe晶体蓝色电致发光的性能,进一步提高ZnSe晶体的纯度是十分重要的。     

用ODLTS法研究ZnSe:Ga晶体中的自激活深能级

本文用光学深能级瞬态谱(ODLTS)方法研究了ZnSe:Ga晶体中的自激活(SA)深受主能级。首次用ODLTS技术测量了ZnSe:Ga晶体中与SA中心相应的深受主能级为0.65eV。文中还研究了该深受主中心在晶体中的空间分布。     

Se+注入ZnSe晶体的深能级研究

将Se离子注入到ZnSe晶体中,用深能级瞬态谱仪(DLTS)测量了注Se+前后ZnSe晶体中深能级的变化,发现在ZnSe中经常出现的分别位于导带下0.30eV和0.33eV的两个能级在注Se+和退火后消失。这个结果进一步证实了Beomi等人提出的以上两个能级分别与Se双空位和包含一个Se单空位的复合体有关的论点。同时注Se+后在导带下0.34eV出现一个新的能级,其电子俘获截面明显区别于0.33eV能级。该能级可能与Se填隙原子或占Zn位的反位Se原子有关。     

ZnSe:A1深能级的研究

为研究ZnSe中的本征缺陷和A1在ZnSe中的深能级行为,首先测量了Znse单晶体中的深能级,发现只存在Ec-0.33eV一个电子陷阱。然后,通过热扩散的方法,在300℃～700℃温度范围内把A1掺杂到ZnSe单晶体中,结果发现存在Ec-0.33eV和Ec-0.70eV两个电子陷阱。本文从缺陷化学角度对ZnSe中的本征缺陷和Ec-0.70eV深能级的结构及起源进行了讨论。     

分子束外延生长ZnSe自组织量子点光、电行为研究

分别应用光致发光、电容电压和深能级瞬态傅里叶谱技术详细研究ZnSe自组织量子点样品的光学和电学行为.光致发光温度关系表明ZnSe量子点的光致发光热猝火过程机理.两步猝火过程的理论较好模拟和解释了相关的实验数据.电容电压测量表明样品表观载流子积累峰出现的深度(样品表面下约100nm处)大约是ZnSe量子点层的位置.深能级瞬态傅里叶谱获得的ZnSe量子点电子基态能级位置为ZnSe导带下的011eV,这与ZnSe量子点光致发光热猝火模型得到的结果一致.     

硒化锌晶体背景深能级的光电容谱

对用国产硒化锌(ZnSe)晶体制成的Au-ZnSe肖特基势垒进行了光电容测量。光子能量hv在0.57～0.61eV范围内的激发光引起单指数型电容瞬变过程。hv在0.67～1.0eV范围内的激发光引起的电容瞬变过程呈现双指数行为。回归分析结果表明样品中存在六个深能级,分别位于导带下方0.55,0.66,0.92,1.19,1.38和1.S2eV处。     

分子束外延生长ZnSe自组织量子点光、电行为研究

分别应用光致发光、电容-电压和深能级瞬态傅里叶谱技术详细研究ZnSe自组织量子点样品的光学和电学行为.光致发光温度关系表明ZnSe量子点的光致发光热猝火过程机理.两步猝火过程的理论较好模拟和解释了相关的实验数据.电容-电压测量表明样品表观载流子积累峰出现的深度(样品表面下约100nm处)大约是ZnSe量子点层的位置.深能级瞬态傅里叶谱获得的ZnSe量子点电子基态能级位置为ZnSe导带下的0.11eV,这与ZnSe量子点光致发光热猝火模型得到的结果一致.     

第一性原理研究CO在Cu(110)表面的吸附

本文采用基于密度泛函理论的第一性原理方法, 并同时考虑范德华力的作用, 计算并分析了CO在Cu(110)表面的吸附情况. 结果表明: 1) CO在两个表面Cu原子的短桥位位置吸附最强, 吸附能为1.28 eV. 第二稳定吸附位置为表面Cu原子的顶位, 吸附能为1.23 eV. CO在其他两个位置, 表面两个Cu的长桥位和表面四个Cu的中心位的吸附要弱一些, 约为0.86 eV 和 0.83 eV. 2) 在Cu表面吸附的CO的C-O键长有部分拉长, 这与较强的吸附能和电荷转移相应. 3) 电荷分析表明所有吸附的CO整体上从衬底上面获得部分电荷, 约为0.2 个电荷.     

第一性原理下铜锰共掺铌酸锂晶体的电子结构和吸收光谱

采用基于密度泛函理论的第一性原理研究了Cu、Mn单掺及共掺LiNbO3晶体的电子结构和光学性质.结果显示,Cu、Mn掺杂LiNbO_3晶体禁带中的杂质能级分别由Cu 3d轨道、Mn 3d轨道贡献;各掺杂体系的带隙均较纯LiNbO_3晶体变窄.共掺晶体中Cu离子形成了较单掺时更浅的能级中心,并在2.87eV处有较强的吸收峰;Mn离子在1.73eV附近的吸收较单掺时减弱且中心略有偏移,在2.24eV处的非光折变峰与Mn~(3+)相关,这对吸收峰的变化被认为与Cu、Mn间电子转移相联系.相对Cu、Fe共掺LiNbO_3晶体,Cu、Mn共掺LiNbO_3晶体可以通过适当提高Cu离子浓度,来改善存储参量中的动态范围和记录灵敏度.由于同一深能级掺杂离子伴以不同浅能级掺离子将呈现出不同的吸收特征并影响存储性能,在共掺离子的配搭选择时对各待选配搭的模拟计算非常必要.     

可变色的ZnSe:Er3+ MIS发光二极管

本文首次利用高场和低场激发下的有效发光中心,设计和制备了随外加电压极性改变而变色的ZoSe:Er3+ MIS发光二极管。这种发光二极管在正向电压激发下得到蓝色发光,而在反向电压激发下得到绿色发光。     

Radiative recombination in ZnTe-CdSe and ZnSe-CdTe heterojunctions

Electroluminescence in II–VI heterojunctions has been investigated. Three types of ZnTe-CdSe heterojunctions were studied depending on the preparation method: Red diodes obtained by doping with O₂, yellow Cu-doped diodes and green undoped heterojunctions. Radiation was observed only in the forward biased junctions. At 80 K the external quantum efficiency is about 1.3% for red ZnTe-CdSe heterojunctions and decreases by one order of magnitude at room temperature. The radiation intensity for the other heterojunctions is the same at 80 K but at 150 K the luminescence disappears. The band diagram and the electroluminescence spectra show that the two-directional injection takes place in the ZnTe-CdSe heterojunctions. The blue electroluminescence for ZnSe-CdTe heterojunctions is due to the injection of hot holes in ZnSe from the high-resistivity layer at the interface and the recombination of these holes with the free electrons through an accepto level at 0.124 eV from the valence band. At 80 K slow periodic current oscillations accompanied by in-phase oscillations of the luminescence have been observed in ZnSe-CdTe heterojunctions.     

CdS单晶中的绿色电致发光和光致发光

在50-290K温度范围内,研究了在正向电压激发下,用高纯CdS单晶制备的MIS发光二极管的电致发光光谱。在室温时,发射光谱分别由峰值为5135±25Å和5300±15Å的二个绿色谱带所组成,而在低温下,观测到有很多结构的光谱。在50K时,自由和束缚激子的发射实际上占有统治地位。文中提出,在室温时,谱峰为5135±25Å的谱带是与受导带自由电子散射的自由激子的发射有关;而谱峰为5300±15Å的谱带归结为与同时发射二个纵光学声子的自由激子的发射有关。比较了刚生长的高阻CdS单晶以及在熔融镉中热处理的低阻CdS单晶的光致发光光谱。在熔融镉中的热处理抑制了自由到束缚(HES)和束缚到束缚(LES)的边缘发射,也抑制了I2束缚激子谱线,但是增强了自由激子的发射,在电场激发下,也使自由激子的发射增强。     

ZnSe:Al发光光谱的研究

本文用热扩散的方法在Zn饱和蒸气压下,把Al掺杂到高纯ZnSe单晶中,通过77K下的光致发光光谱研究了Al杂质的发光行为,讨论了施主一受主对发射强度、自激活中心发射强度随掺杂温度的变化规律以及与Zn饱和蒸气压的关系.本文首次报道了在300℃～900℃温度范围内进行Al掺杂的ZnSe的发光规律.     

X-ray stimulated luminescence in MgO

Studies have been made of the emission spectrum of MgO crystals induced by X-irradiation at 90 K. Two bands (half-widths ～0.8 eV) were observed to peak at 4.95 and 3.2 eV, respectively, in high purity crystals. Doping with 100 ppm or greater of Fe, Co, Cr, Cu, Mn, and Ni suppressed the luminescence, though in the MgO:Ni crystal the 2.3 eV Ni²⁺ band due to the ¹T_2g→³A_2g transition was observed. In deuterium-doped crystals the ratio of the intensity of 3.2–4.95 eV emission was found to be 1.2 as compared to 8 for the undoped crystals. Prior exposure of the pure crystals to ionizing radiation enhances the 4.95 eV band by a factor of three while not affecting the 3.2 eV band. This enhancement of intensity decays in several stages upon standing at room temperature in a way that reflects the thermal stability of the various components of the composite V-band absorption. These facts together with the observation that the 210 K thermoluminescence peak is composed entirely of 4.95 eV emission indicate that this luminescence band is associated with the recombination of an electron with a hole located in a V-type center, i.e. O?□ + e → (O²?□)1 → O²?□ + 4.95 eV, where the square indicates that the perturbing positive ion vacancy is adjacent to the oxugen ion which has captured the hole. In MgO:Li⁺, which exhibits no V-type centers upon irradiation, the 4.95 eV band was absent and a 2.9 eV emission which may be associated with recombination at the [Li]⁰ center was observe.     

Valence band contributions to photoluminescence excitation spectra of tightly bound holes in zincblende semiconductors

Photoluminescence excitation (PLE) spectra of deep acceptor states in ZnSe, for example the Cu-related luminescence band at ≈1.95 eV, contain a prominent excitation band at ≈3.25 eV. This band lies above the structure marking the lowest direct E_O band gap E_g by the spin-orbit splitting energy Δ of the valence bands at Γ. The higher energy feature is either absent or greatly de-emphasised in the PLE spectra of shallow acceptor states in ZnSe and of the oxygen iso-electronic trap in ZnTe, where the electron rather than the hole is tightly bound. However, a significant PLE component at E_g + Δ is observed for deep acceptor-like states in ZnTe, where Δ is ≈0.95 eV. Efficient PLE at E + Δ for luminescence from deep acceptor-like states is shown to be consistent with the extended wave-vector contributions to the bound state wave-functions of holes of binding energies ≈Δ.     

Photocapacitance study of deep centers in ZnSe-based radiating structures

The photocapacitance method is used to study ZnSe-Au and ZnSe-ZnO(SiO₂) barrier structures in order to investigate deep centers in ZnSe crystals annealed in liquid zinc and subjected to additional thermoprocessing in a vacuum. The energy levels of the deep centers producing photocapacitance are determined. In crystals annealed for 4.5 h acceptor levels with ionization energies of 0.28, 0.36, 0.58, and 0.71 eV are found. With increase in anealing period to 100 h only the level with ionization energy of 0.58 eV appears, leading to a decrease in intensity of the yellow-green band and an increase in intensity of blue scintillation in the electroluminescence spectra.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 59–63, July 1984.