GaAs光电阴极在不同强度光照下的稳定性

利用多信息量测试系统分别测试了反射式GaAs光电阴极激活后在0(无光照)，33和100lx白光照射情况下阴极的光电流衰减变化曲线，计算得到其寿命分别为320，160和75min，阴极稳定性随光照强度的增加而降低，测试了只有光照(100lx)而无光电流流过阴极时阴极的寿命为100min. 通过比较发现光照比光电流对阴极稳定性的影响更大. 还测试了阴极在33lx光照下量子效率曲线随时间的衰减，发现阴极低能光子的量子效率下降速度更快，导致量子效率曲线形状不断发生变化. 基于修正后的反射式阴极量子效率公式对这种变化进行了理论分析，发现与光电子的谷间散射和阴极衰减过程中表面势垒形状的变化有关.     

以Au为缓冲层在Si衬底上生长ZnO薄膜

采用化学气相沉积(CVD)方法在Si(001)衬底上分别制备了有金属Au缓冲层以及无Au缓冲层的ZnO薄膜。其中Au缓冲层在物理气相沉积(PVD)设备中蒸发,厚度大约为300nm。有Au缓冲层的ZnO薄膜晶体质量比直接在Si衬底上生长有了显著提高。利用X射线衍射(XRD)研究了所生长ZnO薄膜的结晶质量,有Au缓冲层的ZnO薄膜虽然仍为多晶,但显示出明显的择优取向。用光学显微镜研究了ZnO薄膜的表面特征,金属Au缓冲层显著地提高了在Si衬底上生长的ZnO薄膜的晶粒尺寸及平整度。同时利用室温光致发光(PL)谱研究了ZnO薄膜的光学性质,并分析了有Au缓冲层的ZnO薄膜NEB发光峰强度反而弱的可能原因。     

Variation of Optical Quenching of Photoconductivity with Resistivity in Unintentional Doped GaN

The optical quenching of photoconduetivity under dual illumination in GaN samples with different resistivity is investigated to reveal the variation of deep levels. The samples are grown by metal organic chemical vapour deposition without intentional doping. Quenching bands centered at 1.35 eV, 1.55 eV, 1.98eV, and 2.60 eV are observed. It is found that the 1.98eV quenching band is dominated in all the samples and the 2.60eV band is observed only in the high-resistivity samples. The possible defect levels responsible for the quenching bands and the origin of different quenching behaviour at 2.60eV are discussed. It is suggested that the defect level responsible for quenching at 2.60 eV plays an important role for the enhancement of resistivity.     

Photon—Storage in Optical Memory Cells Based on a Semiconductor Quantum Dot—Quantum Well Hybrid Structure

We report a new type of photonic memory cell based on a semiconductor quantum dot (QD)--quantum well (QW) hybrid structure, in which photo-generated excitons can be decomposed into separated electrons and holes, and stored in QW and QDs respectively. Storage and retrieval of photonic signals are verified by time-resolved photoluminescence experiments. A storage time in excess of l00ms has been obtained at a temperature of 10K while the switching speed reaches the order of ten megahertz.     

The performance enhancement in organic light-emitting diode using a semicrystalline composite for hole injection

A semicrystalline composite, 3, 4, 9, 10 perylenetetracarboxylic dianhydride （PTCDA） doped N,N＇-di（1-naphthyl）- N,N＇-diphenylbenzidine （NPB）, has been fabricated and characterized. An organic light-emitting diode using such a composite in hole injection exhibits the improved performance as compared with the reference device using neat NPB in hole injection. For example, at a luminance of 2000 cd/m2, the former device gives a current efficiency of 2.0cd/A, higher than 1.6cd/A obtained from the latter device. Furthermore, the semicrystalline composite has been shown thermally to be more stable than the neat NPB thin film, which is useful for making organic light emitting diodes with a prolonged lifetime.     

高质量氮化镓材料的光致发光研究

利用氨气源分子束外延（GSMBE）技术,在改型Ⅳ型分子束外延设备上生长高质量GaN单晶外延材料,并对样品进行了光致发光测量。分析室温和低温光致发光谱,系统地研究GaN的发光峰及其起源,并对常见的黄色发光带现象及其微结构起因进行探讨。     

Effect of Stress in GaN/AIInGaN Grown on GaN Templates with Different Stress States

We clarify the effect of the stress in GaN templates on the subsequent AIlnGaN deposition by simply growing 150nm AIInGaN on a 30μm GaN template （sample 1） prepared by hydride vapor phase epitaxy and a 2.3μm thin control GaN template （sample 2） prepared by metalorganic chemical vapor deposition. X-ray diffraction and secondary iron mass spectroscopy measurements reveal the stress states （tensile stress and full relaxed for samples 1 and 2, respectively） and compositions （Al0.169In0.01 Ga0.821N, Al0.171In0.006 Ga0.823N for samples 1 and 2, respectively） of AlInGaN. By carefully eliminating other possible factor, as template surface roughness, it is concluded that different stress states of AlInGaN should stem from different stress states of GaN templates.     

预注入对Si1-xCx合金形成的影响

室温下在单晶Si中注入(0.6—1.5)at%的C原子,部分样品在C离子注入之前在其中注入²⁹Si⁺离子产生损伤,然后在相同条件下利用高温退火固相外延了Si_1-xC_x合金,研究了预注入对Si_1-xC_x合金形成的影响.如果注入C离子的剂量小于引起Si非晶化的剂量,在950℃退火过程中注入产生的损伤缺陷容易与C原子结合形成缺陷团簇,难于形成Si_1-xC关键词： 离子注入 固相外延 1-xC_x合金')" href="#">Si_1-xC_x合金     

离子注入法制备GaN∶Er薄膜的Raman光谱分析

对离子注入法制备的u-,n-和p-GaN∶Er三种类型的薄膜样品进行了Raman光谱分析。Er+注入GaN样品后新出现了293,362和670 cm-1等波数的Raman峰,其中293 cm-1处的Raman峰被指认为无序激活的Raman散射(DARS),362 cm-1和670 cm-1处的Raman峰可能与离子注入后形成的GaN晶格缺陷有关。上述GaN∶Er样品在800℃退火前后的E₂(high)特征峰均向高频方向移动,表明薄膜晶格中均存在着压应力。采用洛伦兹拟合分析了Raman光谱中组成A₁(LO)模式峰的未耦合LO模与等离子体激元耦合模LPP+在不同样品中的出现情况,定性指出了GaN∶Er系列样品中载流子浓度的变化规律。     

High-power near diffraction-limited 1 064-nm Nd:YAG rod laser and second harmonic generation by intracavity-frequency-doubling

We present a near diffraction-limited 1 064-nm Nd:YAG rod laser with output power of 82.3 W(M~2≈1.38). The power fluctuation over two hours is better than±1.1%.Pulsed 1064-nm laser with an average power of 66.6 W and pulse width of 46 ns are achieved when the laser is Q-switched at a repetition rate of 10 kHz.The short pulse duration stems from the short cavity as well as the high-gain laser modules. Using intracavity-frequency-doubling,a 35.0-W near diffraction-limited 532-nm green laser(M~2≈1.32) is achieved with a pulse width of 43 ns.