The interferometric mirage effect method: The determination of the thermal diffusivity of CdMnTe

A Michelson interferometer was used as a precise detector in the Mirage effect configuration in order to determine the thermal diffusivity of the diluted magnetic semiconductor Cd_1−xMn_xTe, in the concentration range 0<x<0.6 at room temperature. This zinc-blende ternary alloy exhibits an almost linear behavior of the thermal diffusivity as a function of Mn concentration. This trend is similar to that of the energy gap against Mn concentration, which increases linearly as the nominal x value increases. The latter result was tested by electrolytic electroreflectance measurements.     

CdTe/CdMnTe多量子阱的生长和激子复合动力学性质的研究

用分子束外延在GaAs衬底上生长了CdTe/Cd0.8Mn0.2Te多量子 结构,利用X射线衍射（XRD）、低激发密度下的PL光谱和变密度激发的ps时间分辨光谱研究了CdTe/CdMnTe多量子阱的结构和激子复合特性。在变密度激发的ps时间分辨光谱中,发现不同激发密度下发光衰减时间不同,认为它的机理可能是无辐射复合引起的。     

Magnetic and photomagnetic properties of polycrystalline wide-gap semiconductor Cd1-xMnxTe thin films

The magnetic and photomagnetic properties of polycrystalline Cd_1-xMn_xTe thin films prepared by radio frequency (rf) sputtering have been investigated. Magnetization measurements were carried out using a rf superconducting quantum interference device magnetometer in the temperature range of 1.8∼300K at various magnetic fields up to 5.5 T. For temperatures above 40K, Curie-Weiss behavior was observed with a negative Weiss constant indicating predominantly antiferromagnetic interactions. Spin-glass transitions occurred at low temperatures. Photoinduced magnetization has been observed when the sample was illuminated by unpolarized light from an optical fiber.     

ACRT-Te溶液Bridgman法生长的In掺杂CdMnTe界面研究(英文)

采用ACRT-Te溶液垂直布里奇曼法成功制备出直径为30mm、长度为60mm的CdMnTe晶锭。相对于普通布里奇曼法生长的CdMnTe晶锭,Te溶液法生长的 CdMnTe晶锭中的孪晶大大减少。但是由于较高的Te夹杂相密度,红外透过成像显示晶锭生长界面的微观形貌既不均匀也不规则。同时,采用激光共聚焦显微镜也观察到CdMnTe富Te区存在无规律沉积的含有孔洞的不规则形状Te相。如果采用合适的生长工艺得到较为平直的生长界面,Te溶液垂直布里奇曼法可以有效减少CdMnTe晶体中的孪晶。     

A study of polycrystalline Cd(Zn,Mn)Te/Cds films and interfaces

Polycrystalline films of Cd_1-x Zn _x Te (x = 0–0.4) and Cd_1-x Mn _x Te (x = 0–0.25) were grown by MBE and MOCVD, respectively, on CdS/SnO₂/glass substrates to investigate their feasibility for solar cell applications. The compositional uniformity and interface quality of the films were analyzed by x-ray diffraction, surface photovoltage, and Auger depth profile measurements to establish a correlation between growth conditions and lattice constant, atomic concentration, and bandgap of the ternary films. MBE-grown polycrystalline Cd_1-x Zn _x Te films showed a linear dependence between Zn/(Cd + Zn) beam flux ratio, Zn concentration in the film, and the bandgap. Polycrystalline Cd_1-x Zn _x Te films grown at 300° C showed good compositional uniformity in contrast to compositionally non-uniform Cd_1-x Mn _x Te films grown by MOCVD in the temperature range of 420–450° C. The MBE-grown Cd_1-x Zn _x Te interface also showed significantly less interdiffusion compared to the MOCVD-grown Cd_1-x Mn _x Te/CdS interface, where preferential exchange between Cd from the CdS layer and Mn from the Cd_1-x Mn _x Te film was observed. The compositional uniformity of MOCVD-grown polycrystalline Cd_1-x Mn _x Te films grown on CdS/SnO₂/glass substrates was found to be a strong function of the growth conditions as well as the Mn source.     

Characterization of CdMnTe radiation detectors using current and charge transients

Charge transport characteristics of Cd_0.95Mn_0.05Te:In radiation detectors have been evaluated by combining time resolved current transient measurements with time of flight charge transient measurements.The shapes of the measured current pulses have been interpreted with respect to a concentration of net positive space-charge, which has resulted in an electric field gradient across the detector bulk.From the recorded current pulses the charge collection efficiency of the detector was found to approach 100%.From the evolution of the charge collection efficiency with applied bias,the electron mobility-lifetime product ofμ_nτ_n =（8.5±0.4）×10^-4 cm²/V has been estimated.The electron transit time was determined using both transient current technique and time of flight measurements in the bias range of 100-1900 V.From the dependence of drift velocity on applied electric field the electron mobility was found to beμ_n =（718±55） cm²/（V·s） at room temperature.     

Transition-metal-doped chalcogenide lasers

Broadly tunable mid-infrared lasers are desirable for a number of scientific, remote-sensing, and military applications. Recently, Cr²⁺-doped chalcogenide lasers have emerged as an attractive source of tunable laser radiation in the 2–3.4-μm region. This paper provides a brief introduction to this field, summarizes key laser work to date, and provides examples of transmission-metaldoped lasers that operate in this region. In particular, recent results with the Cr²⁺:ZnSe laser material are highlighted.     

垂直布里奇曼法CdMnTe晶体生长过程的数值模拟与实验研究

为经济高效获得Cd_1-xMn_xTe晶体垂直布里奇曼法(vertical Bridgman method,VBM)生长条件,基于有限元软件建立二维有限体积数值模型,模拟了VBM生长Cd_1-xMn_xTe的晶体过程;探究坩埚内部熔体的传热、流动以及生长界面变化情况,分析5、10和15 K/cm 3种不同温度梯度条件对固液界面的影响。结果表明,晶体生长初期,固液界面径向流速差较大,从而使生长界面略凹向晶体;随着晶体生长的进行,固液界面逐渐平缓,开始有利于良好晶体的生长;在生长中后期,固液界面变为凸面,随着温度梯度的增大,可以更好地抑制对流,有利于获得高质量晶体。在模拟结果的基础上,调整不同阶段坩埚下降速度,进行Cd_0.9Mn_0.1Te晶体的制备,成功地生长出质量良好的Cd_0.9Mn_0.1Te晶体。     

Study of CdSSe:V and CdMnTe:V photorefractive effect

A large photorefractive effect was measured in CdS_0.8Se_0.2:V and Cd_0.55Mn_0.45Te:V ternary crystals which shows promise for many device applications such as optical signal processing and optical limiting. In this study, we compared the results obtained from two-wave mixing experiments with Cd_0.55Mn_0.45Te:V and CdS_0.8Se_0.2:V crystals at the 633 nm wavelength. As the signal to pump beam ratio was varied from 10⁻¹ to 10⁻⁴, Cd_0.55MN_0.45Te:V and CdS_0.8Se_0.2:V showed a maximum photorefractive gain of 0.17 and 0.20 cm⁻¹, respectively. The grating formation time of both the crystals were measured to be in the milli-second range at an incident intensity of 200 mW/cm².     

应用于核辐射探测器的CdMnTe晶体的缺陷研究

A laser scanning confocal microscope(LSCM) and a field-emission scanning electron microscope(FESEM) were used to study the defects in CdMnTe crystals,such as twin boundaries,Te inclusions,and dislocations. Twin boundaries were usually decorated with Te inclusions,which could induce dislocations.The optical,electrical properties and detector performance of CdMnTe crystals with twins and free of twins were compared.The results showed that the wafers with a high density of twins usually had lower average IR transmittance and poorer crystalline quality.Besides,the energy spectra indicated that twin boundaries in a CdMnTe detector had a negative effect on detector performance;the values of both the energy resolution and(μτ)_e were nearly half of those for a single crystal detector.