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1.
The optical property and injection efficiency of N-face A1GaN based ultraviolet light emitting diodes (UV-LEDs) are studied and compared with Ga-face A1GaN based UV-LEDs. A staircase electron injector is introduced in the N-face AIGaN based UV-LED. The electroluminescence spectra, power-current performance curves, energy band diagrams, carrier concentration and radiative recombination rate are numerically calculated. The results indicate that the N-face UV-LED has a better optical performance than the Ga-face UV-LED, and the injection efficiency is enhanced owing to the fact that the staircase electron injector is available for UV-LEDs.  相似文献   
2.
李世彬  肖战菲  苏元捷  姜晶  居永峰  吴志明  蒋亚东 《物理学报》2012,61(16):163701-163701
材料的载流子浓度和迁移率是影响器件性能的关键因素, 变温Hall测试结果证明杂质掺杂AlGaN中的载流子浓度和迁移率随温度 降低而减小.然而极化诱导掺杂的载流子浓度和迁移率不受温度变化的影响.以准绝缘 的GaN体材料作为衬底, 在组分分层渐变的AlGaN中实现的极化诱导掺杂浓度 仅仅在1017 cm-3数量级甚至更低. 本研究采用载流子浓度为1016 cm-3量级的非有意n型掺杂GaN模板为衬底, 用极化诱导掺杂技术在分子束外延生长的AlGaN薄膜材料中实现了高 达1020 cm-3 量级的超高电子浓度. 准绝缘的体材GaN半导体作衬底时, 只有表面自由电子作为极化掺杂源, 而非有意掺杂的GaN模板衬底除了提供表面自由电子外,还能为极化电场 提供更多的自由电子"源", 从而实现超高载流子浓度的n型掺杂.  相似文献   
3.
本文报道了固相萃取预富集处理样品继以液相色谱分离测定不同形态痕量有机汞的方法.二乙基二硫代氨基甲酸钠(DDTC)作络合剂及甲醇作洗脱液的预富集系统能在线富集甲基汞(MeHg)、乙基汞(EtHg)和苯基汞(PhHg).用于测定加标海水中MeHg、EtHg和PhHg,回收率分别为96.9%、102.4%和98.0%;相对标准偏差分别为3.5%、5.0%和5.0%;检测下限分别为 1.0μg/L、1.2 μg/L和 1.2 μg/L.  相似文献   
4.
Wide bandgap Alx Ga1-x N (x = 0.7-1) p-n junction is realized on a silicon substrate through polarization induced doping. Polarization induced positive charge field is produced by linearly grading from A1N to Al0.7Ga0.3N, and negative charge field is generated by an inverted grading from A10.7Ga0.3N to A1N. The polarization charge field induced hole density is on the order of 10^18 cm^-3 in the graded AIxGaI-xN:Be (x = 0.7-1) p-n junction. Polarization doping provides a feasible way to mass produce lll-nitride devices on silicon substrates.  相似文献   
5.
采用铂电极为加热电阻,研究了厚度为300—370nm等离子体化学气相沉积(PECVD)工艺制备的氢化非晶硅(a-Si:H)薄膜的热导率随衬底温度的变化规律.用光谱式椭偏仪拟合测量薄膜的厚度,得到了沉积速率随衬底温度变化规律,傅里叶红外(FTIR)表征了在KBr晶片衬底上制备的a-Si:H薄膜的红外光谱特性,SiH原子团键合模的震动对热量的吸收降低了薄膜热导率.从动力学角度分析了薄膜热导率随平均温度升高而增大的原因,并比较了声子传播和自由电子移动在a-Si:H薄膜热导率变化上的作用差异. 关键词: 非晶硅 热导率 薄膜 热能  相似文献   
6.
High electronic density is achieved by polarization doping without an impurity dopant in graded AIGaN films. Low specific contact resistance is studied on the polarization-doped A1GaN/GaN heterojunctions by using the transmission line method (TLM). The sheet density of polarization-doped A1GaN/GaN heterojunction is 6 × 10 14 cm-2 at room temperature. The linearly graded material structure is demonstrated by X-ray diffraction. The cartier concentration and mobility are characterized by a temperature-dependent Hall measurement. Multiple-layer metal (Ti/A1/Ti/Au) is deposited and annealed at 650 ℃ to realize the Ohmic contacts on the graded A1GaN/GaN heterojunctions.  相似文献   
7.
We choose 8-hydroxyquinoline derivative-metal complexes(Beq,Mgq,and Znq) as the acceptors(A) and 4,4',4"-tri-(2-methylphenyl phenylamino) triphenylaine(m-MTDATA) as the donor(D) respectively to study the existing energy transfer process in the organic ultraviolet(UV) photodetector(PD),which has an important influence on the sensitivity of PDs.The energy transfer process from D to A without exciplex formation is discussed,differing from the working mechanism of previous PDs with Gaq[Zisheng Su,Wenlian Li,Bei Chu,Tianle Li,Jianzhuo Zhu,Guang Zhang,Fei Yan,Xiao Li,Yiren Chen and Chun-Sing Lee 2008 Appl.Phys.Lett.93 103309)]and REq[J.B.Wang,W.L.Li,B.Chu,L.L.Chen,G.Zhang,Z.S.Su,Y.R.Chen,D.F.Yang,J.Z.Zhu,S.H.Wu,F.Yan,H.H.Liu,C.S.Lee 2010 Org.Electron.111301]used as an A material.Under 365-nm UV irradiation with an intensity of 1.2 mW/cm~2,the m-MTDATA:Beq blend device with a weight ratio of 1:1 shows a response of 192 mAAV with a detectivity of 6.5 × 10~(11) Jones,which exceeds those of PDs based on Mgq(146 mA/W) and Znq(182 mA/W) due to better energy level alignment between m-MTDATA/Beq and lower radiative decay.More photophysics processes of the PDs involved are discussed in detail.  相似文献   
8.
High electronic density is achieved by polarization doping without an impurity dopant in graded AlGaN films. Low specific contact resistance is studied on the polarization-doped AlGaN/GaN heterojunctions by using the transmission line method(TLM). The sheet density of polarization-doped AlGaN/GaN heterojunction is 6×1014cm-2at room temperature.The linearly graded material structure is demonstrated by X-ray diffraction. The carrier concentration and mobility are characterized by a temperature-dependent Hall measurement. Multiple-layer metal(Ti/Al/Ti/Au) is deposited and annealed at 650°C to realize the Ohmic contacts on the graded AlGaN/GaN heterojunctions.  相似文献   
9.
衬底温度对用RF-PECVD法制备的非晶硅薄膜光学性能影响   总被引:1,自引:0,他引:1  
采用射频等离子增强化学气相沉积(RF-PECVD)工艺制备非晶硅(a-Si:H)薄膜, KBr衬底在175-275 ℃范围内变化, 用傅立叶红外光谱仪(FTIR)测试KBr衬底上的薄膜红外光谱峰随衬底温度的变化情况, 结合红外光谱峰的理论分析确定薄膜中氢含量随衬底温度的变化规律. 光谱式椭圆偏振仪中用Forouhi Bloomer (FB)模型拟合得到薄膜的折射率(n), 消光系数(k), 膜厚及光学禁带宽度(Eg), 并用扫描电镜(SEM)断面分析对椭偏仪测试结果的准确性进行验证. 根据Tauc公式推出薄膜的Eg和截止波长, 并和FB模型得到的结果进行了比较, Eg(FB)和Eg(Tauc)的差值在0.015 eV内.  相似文献   
10.
椭偏透射法测量氢化非晶硅薄膜厚度和光学参数   总被引:1,自引:0,他引:1       下载免费PDF全文
针对多角度椭偏测量透明基片上薄膜厚度和光学参数时基片背面非相干反射光的影响问题,报道了利用椭偏透射谱测量等离子增强化学气相沉积法(PECVD)制备的a-Si:H薄膜厚度和光学参数的方法,分析了基片温度Ts和辉光放电前气体温度Tg的影响.研究表明,用椭偏透射法测量的a-Si:H薄膜厚度值与扫描电镜(SEM)测得的值相当,推导得到的光学参数与其他研究者得到的结果一致.该方法可用于生长在透明基片上的其他非晶或多晶薄膜. 关键词: 椭偏测量 透射法 光学参数 氢化非晶硅薄膜  相似文献   
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