GaAs/AlGaAs多量子阱红外探测器的γ辐照研究

本文报道了γ射线辐照对量子阱红外探测器性能的影响。γ射线的辐射剂量分别为１ｍｒａｄ、６ｍｒａｄ、１６ｍｒａｄ。测量了器件在不同γ辐照剂量下的光谱响应、暗电汉、黑体响应率。通过对实验结果的分析,暗电流和黑体响应率随γ辐照剂量增加而递减,表明探测器的性能随γ射线辐照剂量的增加而逐步衰减。     

一种新的X-射线发光光谱测量装置的建立

提出一种由X-射线发生器、光学光纤、荧光光谱仪组成的用于测定X-射线发光材料的新装置.该设备可以测定X-射线发光材料的荧光强度随着波长的变化曲线、荧光强度随着激发时间的变化曲线、余辉衰减随着时间的变化曲线以及余辉时间等.研究了X射线发光材料在不同时间段的光谱特征.     

新型塑料闪烁体探测器对脉冲X射线响应的研究

射线装置产生的X射线脉冲周期长短不一,很多装置会产生短周期脉冲X射线,特别是医院X射线诊断机等。这些装置的最小脉冲宽度为ns级,能量从几到几百KeV。现有的辐射剂量计无法准确测量这种短周期脉冲X射线。因此,文章研究提出一种新的快速响应和更大探测能量的塑料闪烁体探测器针对医院X射线诊断机的检测需求,并与实际应用情况相结合,在对各种探测器进行性能分析的基础上,选用新型塑料闪烁体探测器进行脉冲X射线响应的研究。经过试验,该研究所设计的新型塑料闪烁体探测器检测系统可以较准确地测量医院X射线诊断机的短周期脉冲X射线。     

GaN/6H-SiC紫外探测器的光电流性质研究

本文研究了以金属有机物化学气相沉积方法生长在６Ｈ－ＳｉＣ衬底上的ＧａＮ外延薄膜制成的光导型紫外探测器的光电流性质．通过对其光电流谱的测量，获得了ＧａＮ探测器在紫外波段从２５０～３６５ｎｍ近于平坦的光电流响应曲线，并且观察到在～３．４ｅＶ带边附近陡峭的截止边，即当光波长在从３６５ｎｍ变到３７５ｎｍ的１０ｎｍ区间内，光电流信号下降了３个数量级．在３６０ｎｍ波长处，我们测得ＧａＮ探测器在５Ｖ偏压下光电流响应度为１３３Ａ／Ｗ，并得到了其响应度与外加偏压的关系．通过拟合光电流信号强度与入射光调制频率的实验数据     

X射线线阵探测器校正与滤波

针对X射线线阵探测器像素响应不均而造成X射线图像产生竖条纹,以及由探测器本身和外界产生噪声干扰的问题,提出了一种新型的校正与滤波模型,解决了传统校正方法因忽略噪声影响而使得校正完成后数据波动较大的问题。结合X射线特性及X射线线阵探测器的成像原理,分析了像素响应不均时的输出特性及噪声,建立了改进的两点校正算法与基于偏微分方程的半隐式差分滤波模型。实验证明,分辨率为19 216的X射线线阵探测器在经过该模型校正后,有效地解决了像素响应不均的问题,抑制了噪声的影响,在位深为16 bit的情况下,平均均方误差低于五个灰度级,提高了X射线图像检测的质量。     

物理气相输运法制备碘化铅晶体及其电学与γ射线能谱响应研究

采用物理气相输运法制备了碘化铅晶体并制作了两种不同结构的辐射探测器。论文对室温下器件的电学性质及γ射线响应性能进行了测试。结果表明,当偏置电场与晶体c轴平行时,测得的器件暗电阻为3?1010 Ω?cm,但当偏置电场垂直于晶体c轴时,暗电阻降为2?108Ω?cm 。能谱测试显示,两种结构的探测器对241Am发射的59.5keV γ射线均有敏感的响应,其中性能最好的探测器能量分辨率达到16.8%,半高宽为9.996keV。     

蝶形天线增强的HEMT室温太赫兹探测器

介绍了一种基于GaN/AlGaN高电子迁移率晶体管(HEMT)的高速、高灵敏度室温太赫兹探测器。在太赫兹波辐射下,HEMT源漏端产生直流光电流,并能被栅压灵敏地调控。探测器中新颖的蝶形天线设计使接收到的太赫兹电场得到显著增强,提高了探测器的响应度。通过测量探测器对不同偏振方向的太赫兹光的响应,有效验证了蝶形天线对太赫兹电场的增强作用。室温下,探测器的等效噪声功率约为5×10-10W/Hz21,平均响应度达42mA/W。实验结果表明,光电流的产生与二维电子气沟道的场效应特性和入射太赫兹波电场在电子沟道中的分布密切相关。自混频理论能很好地描述实验结果。     

GaAs粒子探测器对低能X射线的响应

GaAs粒子探测器既能作为高抗辐射的探测器，又能作为X射线的线性传感器。在不同照射量的X射线辐照下，探测器的灵敏度与X射线的照射量是线性关系。探测器的有效面积大、所加反偏电压高，其灵敏度相对也高。该探测器可作为X射线的线性传感器。     

一种新的ZnO/金刚石薄膜结构紫外光探测器

不同晶粒大小、高度c轴取向的氧化锌薄膜通过射频反应磁控溅射法成功地沉积在自支撑金刚石薄膜的成核面上.紫外光辐照下,ZnO/金刚石薄膜结构紫外光探测器有明显的光响应特性.探测器的暗电流、光电流与ZnO薄膜的晶粒尺寸及质量有关.在+10 V偏压条件下,氧化锌薄膜的晶粒尺寸越大,则探测器的暗电流越小而光电流越大.光电流的时间依赖性证实了载流子的陷阱效应.     

石墨烯/硅异质结光电导型探测器光电响应及噪声

设计并制备了石墨烯/硅异质结光电导型光电探测器,重点分析了光电响应与噪声性能。相比纯硅光电导探测器,石墨烯/硅异质结光电导探测器对635 nm波长激光的净光电流从20μA提升至260μA,与此同时,其1 Hz噪声幅值从3.2×10^-17 A²/Hz增加至2.1×10^-16 A²/Hz。进一步比较两种探测器的相对信噪比(净光电流/1 Hz噪声幅值),发现石墨烯/硅异质结探测器的相对信噪比(1.2×10¹⁸)优于纯硅探测器的(6.3×10¹⁷)。此外,探究了石墨烯条带尺寸对于光电响应及噪声的影响,发现随着石墨烯条带长度的增加,探测器的光电响应与噪声呈下降趋势;随着石墨烯条带宽度的增加,探测器的光电响应与噪声呈上升趋势。进一步比较了不同石墨烯条带长宽比探测器的净光电流与相对信噪比,发现净光电流随着长宽比的增大而减小,而相对信噪比随着长宽比的增大而增加。此外,通过沉积Al₂O₃对探测器的噪声进行了抑制。最后,利用栅压调制...     

The Interaction of Laser and Photoconductor in a Continuous-Wave Terahertz Photomixer

The interaction of laser and photoconductor in an optical heterodyne conversion scheme is studied in detail. A dc biased photoconductor excited by two continuous-wave (CW) laser beams with a difference in their central frequencies falling in the terahertz spectrum is considered as the core element in all photoconductive photomixing structures. For this configuration the continuity equations for the electron and hole densities are solved in their general form along with the appropriate boundary conditions to find photocurrent distribution inside the photoconductor. It is shown that in a CW terahertz photomixing scheme the resulting photocurrent contains a dc component and a terahertz component. It is also shown that the amplitude and the phase of the terahertz component of the photocurrent are functions of the applied bias, physical parameters of the photoconductor, parameters of the lasers, and photomixer configuration. The dependency of the photocurrent on all of these parameters is explored in detail for a typical photomixer made of low-temperature-grown GaAs photoconductor.     

Long-wavelength multiple-quantum-well voltage-controlled bistablelaser diodes

We have investigated static and dynamic characteristics of a multiple-quantum-well (MQW) voltage-controlled bistable laser diode at 1.5 μm. Using the quantum confined Stark effect, the absorption coefficient and the absorption band edge of the saturable absorption region are controlled by applied voltage, resulting in easy change of the hysteresis width and the threshold current. Applied voltage from below the current injection regime to the saturable absorption region, typically the reverse bias voltage, allows faster turn-off switching speed due to the carrier sweep-out by the applied electric field, MQW bistable lasers with InGaAs-InP, InGaAs-InGaAsP and InGaAs-InAlAs systems and several kinds of well numbers were fabricated and their threshold current and switching characteristics are compared. A hysteresis width change of about 20 mA was obtained by changing the applied voltage of about 1 V in each case, Less than 100 ps turn-on switching time with injection light of 1-mW peak intensity was obtained. The device can be switched-on by injection light with about 50 nm bandwidth, and the minimum input light switching intensity of less than 10 μW is achieved around the absorption peak wavelength of the saturable absorber. The InGaAs-InAIAs system has the advantage of low voltage bias at the saturable absorber, because the absorption edge is sharper than other materials due to its high conduction band offset. It has a turn-off switching time of less than 100 ps at the applied voltage height of 2.0 V. And also, memory operation with the repetition rate of 2 GHz has been achieved using input light and the applied voltage     

Electrical and optoelectrical properties of CdS-Ge heterojunctions

The electrical and optoelectrical characteristics are presented for n-CdS/p-Ge heterojunctions fabricated by depositing Ge onto (0001) faces of CdS monocrystals. The experimental results are interpreted in terms of an energy band model proposed for this heterojunction. It is found that a Schottky barrier is present on the CdS side of the interface. With an In (injecting) contact to the CdS and an ohmic contact to the Ge, the device acts as a photoconductor in which the current is space-charge-limited for forward bias (Ge positive, CdS negative). For the opposite bias polarity the photoconductivity is reduced substantially and the current is limited by tunneling through the barrier spike in the conduction band. The photoconductivity at room temperature results from electrons being excited in the CdS bulk by photons of 2·34 eV energy. For forward bias the photocurrent is found to be proportional to the light intensity at moderate voltages, as for a normal photoconductor. However, at low voltages the photocurrent is found to be proportional to the two-thirds power of the light intensity.     

磁控溅射AlN∶Mg/ZnO∶Al异质结二极管及其光电特性的研究

利用磁控溅射方法,在ITO玻璃基底上分别溅射镁掺杂的氮化铝(AlN∶Mg)薄膜、铝掺杂的氧化锌(ZnO∶Al或AZO)薄膜,成功制备AlN∶Mg/ZnO∶Al透明异质结二极管.实验结果表明:AlN∶Mg/ZnO∶Al异质结具有明显的Ⅰ-Ⅴ整流特性,正向开启电压1V左右,在氙灯光照下,二极管的反向电流在5V偏置时达到3m...     

A solid-state image converter

AnEL-PCimage converter has been designed to convert the near-IR radiation obtained from light-emitting semiconductor diodes into visible radiation. In addition to wavelength conversion, a quantum gain was also obtained. High contrast ratios are shown to be dependent upon photoconductor capacitance. Concentric, noncoplanar electrode structures have been utilized to achieve photoconductor capacitance values several orders of magnitude smaller than those of a correspondingELelement. Data are shown describing the intensifier operation as a function of applied voltage and frequency. The input-output transfer function shows operation over three orders of magnitude of input intensity. Peak optical gains of 150 are reported.     

Spontaneous oscillations and chaos in silicon induced by excitonic impact ionization

We have observed spontaneous photocurrent oscillations leading to chaos in boron doped Czochralski silicon under optical excitation at liquid helium temperatures. The silicon samples have been annealed at 450°C for more than 100 hours to contain thermal donor complexes in a concentration of about 10¹⁶/cm³. The oscillations start at a certain critical electric field, where the impact ionization of the thermal donor bound excitons by hot free carriers set in. The current-voltage characteristic shows a highly nonlinear behaviour with a negative differential resistance. Near the breakdown region, which is close to 150 V/cm at 2 K, the current oscillates between a few mA to some hundred mA in pulses of less than a microsecond at a frequency of around 10 kHz, critically dependent on the external parameters like the applied voltage, temperature, laser excitation intensity or the specific sample used. The physical mechanism causing these oscillations is suggested to be a critical balance between the impact ionization- and capture- rates of the thermal donor bound excitons.     

高温AlN为模板的AlGaN基p-i-n背照式日光盲探测器

第一次报道了以高温AlN为模板层的AlGaN基p-i-n背照式日光盲探测器的制作和器件特性.利用MOCVD方法在(0001)面的蓝宝石衬底上生长了探测器的AlxGa1-xN多层外延材料.在无需核化层的高温AlN模板上生长了p-i-n背照式日光盲探测器的无裂纹高Al组分(0.7)AlGaN多层外延结构.利用在线反射监测仪、三轴X射线衍射及原子力显微镜表征了外延材料的晶体质量.在1.8V的反向偏压下,制作的探测器表现出了日光盲响应特性,在270nm处最大响应度为0.0864A/W.具有约3.5V的正向开启电压,大于20V的反向击穿电压,在2V的反向偏压下暗电流小于20pA.     

高温AlN为模板的AlGaN基p-i-n背照式日光盲探测器

第一次报道了以高温AlN为模板层的AlGaN基p-i-n背照式日光盲探测器的制作和器件特性.利用MOCVD方法在(0001)面的蓝宝石衬底上生长了探测器的AlxGa1-xN多层外延材料.在无需核化层的高温AlN模板上生长了p-i-n背照式日光盲探测器的无裂纹高Al组分(0.7)AlGaN多层外延结构.利用在线反射监测仪、三轴X射线衍射及原子力显微镜表征了外延材料的晶体质量.在1.8V的反向偏压下,制作的探测器表现出了日光盲响应特性,在270nm处最大响应度为0.0864A/W.具有约3.5V的正向开启电压,大于20V的反向击穿电压,在2V的反向偏压下暗电流小于20pA.     

InGaN/GaN MQW p–n junction photodetectors

InGaN/GaN multiquantum well (MQW) p–n junction photodetectors with semi-transparent Ni/Au electrodes were fabricated and characterized. It was found that the fabricated InGaN/GaN MQW p–n junction photodetectors exhibit a 20 V breakdown voltage and a 3.5 V forward 20 mA turn on voltage. It was also found that the photocurrent to dark current contrast ratio is higher than 10⁵ when a 0.4 V reverse bias was applied to the InGaN/GaN MQW p–n junction photodetectors. Furthermore, it was found that the maximum responsivity was 1.28 and 1.76 A/W with a 0.1 and 3 V applied reverse bias, respectively.     

GaAs MSM结构光电探测器的光电特性研究

报导了作者研制的GaAs MSM—PD的直流及脉冲光电特性,对不同材料、不同结构尺寸的器件进行了试验和分析,测试结果:最大暗电流1.9nA,最高灵敏度为0.25A/W,FWHM小于110 ps(10V下),有较好的光电流和光功率线性关系,通过实验研究,发现对插指结构的器件在同一面积下受光面积与单位面积上的光电流存在最优化选择。