MOCVD法制备的p-ZnO/n-SiC 异质结器件及其电致发光性能

采用光辅助金属有机化学汽相沉积(PA-MOCVD)法在n-SiC(6H)衬底上制备出As掺杂的p型ZnO薄膜,并制备出相应的p-ZnO:As/n-SiC异质结器件。X射线衍射(XRD)和光致发光(PL)测试表明,ZnO薄膜具有较好的结构和光学特性。电流-电压(I-V)测试结果表明,该型异质结器件具有良好的整流特性,开启电压为5.0 V,反向击穿电压约为-13 V。正向偏压下,器件的电致发光(EL)谱表现出两个分别位于紫外和可见光区域的发光峰,通过和ZnO、SiC的PL谱对照,证实异质结器件的发光峰来源于ZnO侧的辐射复合。     

衬底位置对化学气相沉积法制备的磷掺杂p型ZnO纳米材料形貌和特性的影响

采用化学气相沉积方法,在无催化剂的条件下,通过改变衬底位置在Si(100)衬底上制备出了高取向的磷掺杂ZnO纳米线和纳米钉.测试结果表明,当衬底位于反应源上方1.5 cm处时,所制备的样品为钉状结构,而当衬底位于反应源下方1 cm处时样品为线状结构.对不同形貌磷掺杂ZnO纳米结构的生长机理进行了研究.此外,在ZnO纳米结构的低温光致发光谱中观测到了一系列与磷掺杂相关的受主发光峰.还对磷掺杂ZnO纳米结构/n-Si异质结I-V曲线进行了测试,结果表明,该器件具有良好的整流特性,纳米线和纳米钉异质结器件的开启电压分别为4.8和3.2 V.     

不同Sb含量p-SnO2薄膜的制备和特性

采用化学气相沉积方法, 利用Sb₂O₃/SnO作为源材料, 在蓝宝石衬底上制备出不同Sb掺杂量的SnO₂薄膜, 并在此基础上制作出p-SnO₂:Sb/n-SnO₂同质p-n 结器件. 研究表明, 随着Sb含量的增加, 样品表面变得平滑, 晶粒尺寸逐渐增大, 且晶体质量有所改善, 发现少量Sb的掺入可以起到表面活化剂的作用. Hall测量结果证实适量Sb的掺杂可以使SnO₂呈现p型导电特性, 当Sb₂O₃/SnO的质量比为1:5时, 其电学参数为最佳值. 此外, p-SnO₂:Sb/n-SnO₂同质p-n结器件展现出良好的整流特性, 其正向开启电压为3.4 V.     

N离子注入富氧ZnO薄膜的p型导电及拉曼特性研究

采用射频磁控溅射法在富氧环境下制备ZnO薄膜, 继而结合N离子注入及热退火实现薄膜的N掺杂及p 型转变, 借助霍尔测试和拉曼光谱研究了N离子注入富氧ZnO薄膜的p型导电及拉曼特性. 结果表明, 在 600 ℃温度下退火120 min可获得性能较优的p-ZnO: N薄膜, 其空穴浓度约为2.527×10¹⁷ cm^-3. N离子注入ZnO引入了三个附加拉曼振动模, 分别位于274.2, 506.7和640.4 cm^-1. 结合电学及拉曼光谱的分析发现, 退火过程中施主缺陷与N受主之间的相互作用对p-ZnO的形成产生重要影响.     

ZnO纳米线二极管发光器件制备及特性研究

运用液相法生长成ZnO纳米线薄膜,并利用肖特基型异质结的发光原理,构造成功肖特基型ZnO纳米线二极管发光器件.在大于6V直流电压驱动下,观察到近紫外波段392nm处和可见光波段525nm的发射谱带.从单向导电特性及ZnO纳米线材料的能带结构等方面探讨了该种器件的电致发光机理. 关键词： ZnO纳米线 肖特基二极管 电致发光     

溶胶-凝胶法制备Li-N双掺p型ZnO薄膜的结构、光学和电学性能

采用溶胶-凝胶法在n型Si(100)衬底上沉积Li-N双掺杂ZnO薄膜,经X射线衍射和扫描电镜图片分析,所制备薄膜具有多晶纤锌矿结构和高的c轴择优取向.室温下霍尔效应测试结果显示Li-N双掺杂ZnO薄膜具有p型导电特性.在Li掺杂量为15.0at%,Li/N（摩尔比）为1∶1,700℃退火等优化条件下得到的最佳电学性能结果是：电阻率为0.34 Ω·cm,霍尔迁移率为16.43 cm²/V·s,载流子浓度为2.79×10¹⁹ cm^{-3关键词： Li-N双掺 p型ZnO薄膜 溶胶-凝胶 性能}     

退火对ZnO薄膜晶体结构和ZnO/p-Si异质结光电性质的影响

采用脉冲激光沉积方法在p-Si(100)衬底卜牛长ZnO薄膜,分别在500℃、600℃和700℃下真空退火,采用X射线衍射仪研究了退火对ZnO薄膜品体结构的影响,并测量了ZnO的面电阻和ZnO/p-Si异质结的、I-V特性曲线.研究表明,随着退火温度的升高,ZnO的(002)衍射峰强度逐渐增大,半峰全宽不断减小,同时薄膜内应力减小,ZnO晶粒尺寸变大.表明高温退火有助于ZnO薄膜结晶质量的提高.在没有光照的条件下,异质结的漏电流随退火温度的增加而增大;用650 nm光照射样品时,600℃退火的样品表现出最明显的光电效应,而过高的退火温度会破坏ZnO/p-Si异质结的界面结构,使其光电流变小.所以,要得到性能良好的光电器件,应选取适当的退火温度.     

Al和Sb共掺对ZnO有序阵列薄膜的结构和光学性能的影响

采用水热合成法在预先生长的ZnO种子层的玻璃衬底上制备出Al和Sb共掺ZnO纳米棒有序阵列薄膜. 通过X射线衍射、扫描电镜、透射电镜和选区电子衍射分析表明:所制备的薄膜由垂直于ZnO种子层的纳米棒组成, 呈单晶六角纤锌矿ZnO结构, 且沿[001]方向择优生长, 纳米棒的平均直径和长度分别为27.8 nm和1.02 μm. Al和Sb共掺ZnO纳米棒有序阵列薄膜的拉曼散射分析表明:相对于未掺杂ZnO薄膜的拉曼振动峰(580 cm^-1), Al和Sb共掺ZnO阵列薄膜的E₁(LO)振动模式存在拉曼位移. 当Al和Sb的掺杂量为3.0at%,4.0at%,5.0at%,6.0at%时, Al和Sb共掺ZnO阵列薄膜的拉曼振动峰的位移量分别为3,10,14,12 cm^-1. E₁ (LO) 振动模式位移是由Al和Sb掺杂ZnO产生的缺陷引起的. 室温光致发光结果表明:掺杂Al和Sb后, ZnO薄膜在545 nm处的发光强度减小,在414 nm处的发光强度增加. 这是由于掺杂Al和Sb后, ZnO薄膜中Zn_i缺陷增加, O_i缺陷减少引起的. 关键词： Al和Sb共掺ZnO薄膜 纳米棒有序阵列 结构表征 拉曼散射     

n-Ga2O3/p-GaAs异质结日盲紫外探测器制备

采用金属有机化学气相沉积(MOCVD)工艺在p-GaAs(100)衬底上外延了Ga₂O₃薄膜并制备了n-Ga₂O₃/p-GaAs异质结日盲紫外探测器。通过X射线衍射仪、原子力显微镜、场发射扫描电子显微镜等方法对Ga₂O₃薄膜表面形貌、晶体质量进行了测试与分析。结果表明,Ga₂O₃薄膜呈单一晶向,薄膜表面平整且为Volmer-Weber模式外延。测试表明,n-Ga₂O₃/p-GaAs异质结探测器具有明显的整流特性。器件在5 V反向偏压和紫外光(254 nm)照射下实现了超过3.0×10⁴的光暗电流比、7.0 A/W的响应度、3412%的外量子效率、4.6×10¹³ Jones的探测率。我们利用TCAD软件对器件结构进行仿真,得到了器件内的电场分布和能带结构,并分析了器件的工作原理。该异质结探测器性能较好,制造工艺简单,为Ga     

TiO_2薄膜的硼掺杂对TiO_2/p~+-Si异质结器件电致发光的增强

利用磁控溅射在重掺硼硅(p+-Si)衬底上分别沉积TiO2薄膜和掺硼的TiO2(Ti O2∶B)薄膜,并经过氧气氛下600℃热处理,由此形成相应的TiO2/p+-Si和TiO2∶B/p+-Si异质结。与Ti O2/p+-Si异质结器件相比,TiO2∶B/p+-Si异质结器件的电致发光有明显的增强。分析认为:TiO2∶B薄膜经过热处理后,B原子进入TiO2晶格的间隙位,引入了额外的氧空位,而氧空位是TiO2/p+-Si异质结器件电致发光的发光中心,所以上述由B掺杂引起的氧空位浓度的增加是TiO2∶B/p+-Si异质结器件电致发光增强的原因。     

Ultraviolet electroluminescence from ZnO-based light-emitting diode with p-ZnO:N/n-GaN:Si heterojunction structure

A p-ZnO:N/n-GaN:Si structure heterojunction light-emitting diode (LED) is fabricated on c-plane sapphire by full metal organic chemical vapor deposition (MOCVD) technique. The p-type layer with hole concentration of 8.94×10¹⁶ cm⁻³ is composed of nitrogen-doped ZnO using NH₃ as the doping source with subsequent annealing in N₂O plasma ambient. Silicon-doped GaN film with electron concentration of 1.15×10¹⁸ cm⁻³ is used as the n-type layer. Desirable rectifying behavior is observed from the current-voltage (I-V) curve of the device. The forward turn on voltage is about 4 V and the reverse breakdown voltage is more than 7 V. A distinct ultraviolet (UV) electroluminescence (EL) with a dominant emission peak centered at 390 nm is detected at room temperature from the heterojunction structure under forward bias conditions. The origins of the EL emissions are discussed in comparison with the photoluminescence (PL) spectra.     

Formation of Al-N co-doped p-ZnO/n-Si (1 0 0) heterojunction structure by RF co-sputtering technique

Al-N co-doped ZnO (ZnO:Al-N) thin films were grown on n-Si (1 0 0) substrate by RF co-sputtering technique. As-grown ZnO:Al-N film exhibited n-type conductivity whereas on annealing in Ar ambient the conduction of ZnO:Al-N film changes to p-type, typically at 600 °C the high hole concentration of ZnO:Al-N co-doped film was found to be 2.86 × 10¹⁹ cm⁻³ and a low resistivity of 1.85 × 10⁻² Ω-cm. The current-voltage characteristics of the obtained p-ZnO:Al-N/n-Si heterojunction showed good diode like rectifying behavior. Room temperature photoluminescence spectra of annealed co-doped films revealed a dominant peak at 3.24 eV.     

The fabrication and photoresponse of ZnO/diamond film heterojunction diode

Boron-doped p-type freestanding diamond (FSD) films were prepared by hot filament chemical vapor deposition (HFCVD) method. The effect of B/C ratio on the electrical properties of FSD films was investigated by Hall effect measurement system. A ZnO/diamond heterojunction diode was fabricated successfully by depositing n-type ZnO films on the p-type FSD substrate by radio-frequency (RF) magnetron sputtering method. The wavelength dependent photoresponse properties of the heterojunction diode were investigated by studying the effect of light illumination on current-voltage (I-V) characteristics and photocurrent spectra at room temperature. The diode showed a significant discrimination between ultraviolet (UV) and the visible light under reverse bias conditions and photoresponse of the device was approximately linear related to the increasing reverse bias voltages.     

Electroluminescence from ZnO nanowire-based p-GaN/n-ZnO heterojunction light-emitting diodes

Vertically aligned ZnO nanowires were successfully grown on the sapphire substrate by nanoparticle-assisted pulsed laser deposition (NAPLD), which were employed in fabricating the ZnO nanowire-based heterojunction structures. p-GaN/n-ZnO heterojunction light-emitting diodes (LEDs) with embedded ZnO nanowires were obtained by fabricating p-GaN:Mg film/ZnO nanowire/n-ZnO film structures. The current–voltage measurements showed a typical diode characteristic with a threshold voltage of about 2.5 V. Electroluminescence (EL) emission having the wavelength of about 380 nm was observed under forward bias in the heterojunction diodes and was intensified by increasing the applied voltage up to 30 V.     

Room temperature electroluminescence from ZnO/Si heterojunction devices grown by metal-organic chemical vapor deposition

Heterojunction light-emitting diodes with ZnO/Si structure were fabricated on both high-resistivity (p) and low-resistivity (p⁺) Si substrates by metal-organic chemical vapor deposition technology. Fairly good rectifications were observed from the current-voltage curves of both heterojunctions. Ultraviolet (UV) and blue-white electroluminescence (EL) from ZnO layer were observed only from ZnO/p⁺-Si heterojunction under forward bias at room temperature (RT), while strong infrared (IR) EL emissions from Si substrates were detected from both ZnO/p-Si and ZnO/p⁺-Si heterojunctions. The UV and IR EL mechanisms have been explained by energy band structures. The realization of RT EL in UV-visible and IR region on Si substrate has great applicable potential for Si-based optoelectronic integrated circuits.     

Third-harmonic generation from ZnO films deposited by MOCVD

Third-harmonic generation (THG) was studied from ZnO thin film deposited by the metalorganic chemical vapor deposition (MOCVD) technique on sapphire substrates at different temperatures. A strong THG signal was obtained from the film deposited at an appropriate temperature. The dependence of THG on the deposition temperatures was discussed. A third-order susceptibility ⁽³⁾=3.77×10^-12 esu was deduced for a film deposited at 250 °C. This value is similar to that observed from ZnO nanocrystalline films fabricated by pulse-laser deposition (PLD). We conclude that film structure and the crystalline quality is main factors determined the THG in the film. PACS 42.55. Sa; 77.80.-e; 42.55.Px     

Characteristics of SrBi2Ta2O9 ferroelectric films on Si using LaAlO3 thin film as an insulator

Metal–ferroelectric–insulator–semiconductor structures using LaAlO₃ (LAO) layers as an insulating barrier have been investigated. LAO films were deposited on n-Si substrates by low-pressure metalorganic chemical vapor deposition (MOCVD). SrBi₂Ta₂O₉ (SBT) films were prepared as ferroelectric layers at a low processing temperature of 650 °C by a metalorganic decomposition method. The MOCVD-derived LAO buffer layer shows an amorphous structure, relatively high dielectric constant, and good electrical properties. Au/SBT/LAO/n-Si exhibits a larger counterclockwise C–V memory window of 3.7 V and a lower leakage-current density of 2.5×10^-8 A/cm² at an applied voltage of 10 V. It has been confirmed that the hysteresis loop is caused by ferroelectricity. The Auger electron spectrometry depth profile indicates that the introduction of the LAO buffer layer prevents the interfacial diffusion between SBT and the Si substrate effectively and improves the interface quality. PACS 77.84.Dy; 81.15.Fg     

Realization of Ultraviolet Electroluminescence from ZnO Homojunction Fabricated on Silicon Substrate with p-Type ZnO:N Layer Formed by Radical N2O Doping

ZnO homojunction light-emitting diodes are fabricated on Si（100） substrates by plasma assisted metal organic chemical vapour deposition. A p-type layer of nitrogen-doped ZnO film is formed using radical N2O as the acceptor precursor. The n-type ZnO layer is composed of un-doped ZnO film. The device exhibits desirable rectifying behaviour with a turn-on voltage of 3.3 V and a reverse breakdown voltage higher than 6 V. Distinct electrolumineseence emissions centred at 395nm and 490nm are detected from this device at forward current higher than 20mA at room temperature.     

Optical and electrical properties of p-type ZnO fabricated by NH3 plasma post-treated ZnO thin films

In this paper, a simple method is reported to obtain nitrogen-doped p-ZnO film. In this method NH₃ plasma, generated in a plasma-enhanced chemical vapor deposition system, was employed to treat ZnO thin film. By Hall-effect measurement, a p-type conductivity was observed for the treated film with the hole density of 2.2 × 10¹⁶ cm⁻³. X-ray photoelectron spectroscopy (XPS) results confirmed that nitrogen was incorporated into ZnO film during the treatment process to occupy the oxygen positions. In low temperature photoluminescence spectra, an emission peak corresponding to acceptor-donor pair was observed. From this emission peak we calculated the N-related acceptor binding energy to be 130 meV.