Voltage-tunable SiO2-isolated a-SiC:H and/or a-SiN:H p–i–n thin-film LEDs fabricated on c-Si

A voltage-tunable amorphous p–i–n thin-film light emitting diodes (TFLEDs) with SiO₂-isolation on n⁺-type crystalline silicon (c-Si) has been proposed and fabricated successfully. The structure of the device with i-a-SiC:H and i-a-SiN:H luminescent layers is indium–tin–oxide (ITO)/p⁺-a-Si:H/p⁺-a-SiC:H/i-a-SiC:H/i-a-SiN:H/n⁺-a-SiCGe: H/n⁺-a-SiC:H/n⁺-c-Si/Al. This device revealed a brightness of 695 cd/m² at an injection current density of 300 mA/cm². Its EL (electroluminescence) peak wavelength exhibited blue-shift from 655 to 565 nm with applied forward-bias (V) increasing from 15 to 19 V, but the EL peak wavelength was red-shifted from 565 to 670 nm with further increase of V from 19 to 23 V. By comparing with the EL spectra from p–i–n TFLEDs with i-a-SiC:H or i-a-SiN:H luminescent layer only, the EL spectrum of this TFLED could consist of three bands of radiations from the tail-to-tail-state recombinations in (1) i-a-SiC:H layer, (2) i-a-SiN:H layer, and (3) i-a-SiC:H/p⁺-a-SiC:H junction.     

Alternating-Current White Thin-Film Light-Emitting Diodes Based on Hydrogenated Amorphous Carbon Layer

Alternating-current white thin-film light-emitting diodes (ACW-TFLEDs) have been fabricated and demonstrated with composition-graded hydrogenated intrinsic amorphous silicon carbide (i-a-SiC : H) layers. It was found that H₂-plasma treatment of luminescent i-a-C : H layer played an important role in decreasing the ACW-TFLED electroluminescence (EL) threshold voltage, increasing the brightness, and broadening the EL spectrum. The EL spectra of the ACW-TFLED under either dc forward or reverse bias, or the sinusoidal alternating-current voltage were qualitatively very similar, with a peak wavelength at about 505 nm and a broad full-width at half maximum (FWHM) about 240 nm. This device revealed a brightness about 800(500)cd/m² under dc forward (reverse) bias at an injection current density of 600 mA/cm²     

Optoelectronic characteristics of a-SiC:H-based P-I-N thin-filmlight-emitting diodes with low-resistance and high-reflectance N+-a-SiCGe:H layer

The graded-gap a-SiC:H-based p-i-n thin-film light-emitting diodes (TFLEDs) with an additional low-resistance and high-reflectance n⁺ -a-SiCGe:H layer were proposed and fabricated on indium-tin-oxide (ITO)-coated glass substrate in this paper. For a finished TFLED, a brightness of 720 cd/m² could be obtained at an injection current density of 600 mA/cm², and its EL (electroluminescence) threshold voltage was lowered to 8.6 V. In addition, the effects of reflectance and resistance of a-SiCGe:H film on the performance of TFLED were discussed. The optimum rapid thermal annealing (RTA) conditions for fabrication of TFLED after metallization were also studied and employed to improve the optoelectronic characteristics of TFLED     

Electroluminescence characteristics and current-conductionmechanism of a-SiC:H p-i-n thin-film light-emitting diodes with barrierlayer inserted at p-i interface

In order to improve the electroluminescence (EL) characteristics of the hydrogenated amorphous silicon carbide (a-SiC:H) p-i-n thin-film light-emitting diode (TFLED), a barrier layer (BL) was inserted at its p-i interface to enhance the hole injection efficiency under forward-bias operation. The a-SiC:H TFLED's with various optical gaps of BL had been fabricated and characterized. In addition, a composition-graded n⁺-layer was used to reduce its series and contact resistances to the Al electrode and hence the EL threshold voltage (V_th) of an a-SiC:H BL TFLED. The highest obtainable brightness of an a-SiC:H BL TFLED was 342 cd/m² at an injection current density of 600 mA/cm² and the lowest EL V _th achievable was 6.0 V. The current-conduction mechanism of an a-SiC:H BL TFLED had also been investigated. Within the lower applied-bias region, it showed an ohmic current, while within the higher applied-bias region, a space-charge-limited current (SCLC) was observed     

Graded-gap a-SiC:H p-i-n thin-film light-emitting diodes

To improve the performance of hydrogenated amorphous-silicon carbide (a-SiC:H) p-i-n thin-film light-emitting diodes (TFLEDs), a p-i-n TFLED with a graded p-i junction was proposed and fabricated. The electroluminescence (EL) intensity of the proposed TFLED was more than 100 times higher than that of the basic p-i-n TFLED and about 35 times lower than that of the conventional green LED, at the same injection current density. This significant improvement is attributed to the better interface property and enhancement of hole injection efficiency by using the graded-gap p-i junction     

Hydrogenated amorphous silicon carbide double graded-gap p-i-nthin-film light-emitting diodes

Hydrogenated amorphous silicon carbide (a-SiC:H) p-i-n thin-film light-emitting diodes (TFLEDs) with graded p⁺-i and i-n⁺ junctions have been proposed and fabricated successfully on an indium-tin-oxide (ITO)-coated glass. An orange TFLED reveals a brightness of 207 cd/m² at an injection current density of 500 mA/cm². This significant increase of brightness could be ascribed to the combined effect of reduced interface states by using the graded-gap junctions, lower contact resistance due to post-metallization annealing, and higher optical gaps of the doped layers     

蓝光GaN基Micro-LED芯片制备及激光剥离工艺研究

基于半导体制造工艺,制备了尺寸为50μm×80μm的蓝光氮化镓(GaN)基MicroLED芯片。芯片的正向导通电压在2.55V左右;测试了10颗LED芯片在1mA注入电流下的电压值,得到的最大值和最小值分别为3.24和3.12V,波动幅度在4%以内。在1mA的测试电流下,测试芯片的EL光谱峰值波长和半高宽分别为453和14.4nm,芯片的外量子效率可达12.38%,芯片发光均匀且亮度很大。测试结果表明,所制备的Micro-LED芯片具有优异的光电性能。此外,通过激光剥离技术,实现了Micro-LED芯片的转移。研究了激光剥离工艺对MicroLED芯片光电性能的影响,发现在优化的工艺条件下,激光剥离对芯片的光电性能几乎无影响。这些结果有助于小间距微尺寸LED芯片阵列及显示技术的研究。     

Gaq3有机薄膜电致发光器件

首次报道了采用８－羟基喹啉镓螯合物作为发光层制备有机薄膜电致发光器件，器件的结构为：ＩＴＯ导电玻璃／ＴＰＤ／Ｇａｑ３／Ａｌ。研究了Ｇａｑ３薄膜的光致发光和器件的电致发光机理，同时测量和研究了器件的电流密度－－电压（Ｊ－Ｖ）特性和发光亮度－电压（Ｂ－Ｖ）特性。结果表明器件的电致发光峰值波长为５４０ｎｍ，在２０Ｖ直流电压驱动下的最大发光亮度约２５００ｃｄ／ｍ＾２明显高于上同结构和工艺参数制备的Ａｌｑ３     

Low-threshold-voltage thin-film electroluminescent devices

ZnS: Mn thin-film electroluminescent (EL) devices having a low-threshold voltage of about 50 V have been developed by utilizing ferroelectric PbTiO3a and PLT thin films as insulating layers. The ferroelectric PbTiO3and PLT thin film have a considerably high dielectric constant of 190, above 80-percent transparency, and breakdown strength of more than 500 kV/cm. The threshold voltages of 45 and 60 V have been achieved by the device using PLT and PbTiO3thin films, respectively. These values are approximately four times lower than those of reported thin-film EL devices. The developed EL device provides the practical available level of brightness, typically 300 fL at 60 V with the maximum level of more than 800 fL. A typical luminous efficiency is measured as 2.7 lm/W. The very slight change in the threshold voltage during an initial aging treatment is found to be less than 10 V, which is about one order of magnitude smaller than that observed in the conventional EL device using an Y2O3thin film as the insulating layer. A series of technical data on the fabrication processes of the PbTiO3and PLT thin films and performances of the developed EL device have been presented and discussed.     

Visible electroluminescence from stain-etched porous Si diodes

Visible electroluminescence (EL) from stain-etched porous silicon (PoSi) films is presented. The PoSi thin layers (~200 nm) were obtained by stain-etching of B-doped 6-16 Ω-cm (100) crystalline Si in a HF:HNO₃:H₂O (1:3:5) solution. Indium tin oxide (ITO) films of ~2500 Å were used to form a Schottky contact. Visible EL was observed at room temperature from the diode under forward bias. EL onset bias as low as 3 mA/cm² was measured. The EL, with an emission peak at ~640 nm, is similar to the photoluminescence under UV excitation, indicating the same luminescent centers. This result demonstrates a promising and simple technique for the fabrication of PoSi-based light emitting diodes and flat panel display devices     

掺氧氮化硅发光二极管的发光特性研究

采用等离子体增强化学气相沉积方法低温制备非晶氮化硅薄膜,在低温下以氧气为气源,等离子体氧化非晶氮化硅薄膜,以这层薄作为有源层制备电致发光器件。实验结果表明以此方法制备的器件在正向偏置电压下可观测到强烈的黄绿光,发光峰位于540 nm,而且电致发光开启电压低,仅为6 V,功耗小。光致发光谱和电致发光谱测量表明发光来自同一种发光中心,即与Si-O相关的发光中心。     

肖特基型β-Ga2O3日盲紫外光电探测器

本文制备并研究了肖特基型β-Ga₂O₃日盲紫外光电探测器.结果表明：通过脉冲激光沉积外延生长的β-Ga₂O₃的（-201）晶面 X射线衍射峰半高宽仅为36 arcsec,表现出了高的晶体质量;光暗条件下的I-V曲线显示所制备的器件具有明显的肖特基整流特性,在-5V偏压下暗电流保持在0.1nA量级,正向导通电压为1.5V;光电流谱显示器件在240nm处存在显著的峰值响应,并在260nm左右呈现陡峭的截止边,日盲紫外的带内带外抑制比达到1000.同时,也研究了不同掺杂对Ga₂O₃晶体质量的影响.     

掺杂浓度对ZnS∶Er~(3+)EL器件发光特性的影响

研究了ZnS：Er3+薄膜电致发光（EL）器件中，不同Er3+掺杂浓度的发光特性。发现，随发光中心Er3+的浓度增加而红色发光峰相对两个绿色峰有所增强，而两个绿色峰的相对强度却不变，在器件结构相同的情况下，浓度低于5×10－3克分子浓度时发光随浓度的增加而增强，两个绿色峰的亮度没有红色峰的亮度增加幅度大。当浓度大于1×10－2克分子浓度时，绿色发光峰的强度开始下降，红色峰的强度明显增强。说明，发光器件中存在交叉弛豫现象。     

透明叠层结构Ag/MoO_3/Ag阳极对绿光OLED器件性能的影响

本文采用一种结构为Ag/MoO_3/Ag的金属/氧化物/金属(M_1/O/M_2)叠层替代ITO作为OLED器件的阳极,研究Ag/MoO_3/Ag叠层结构变化对于OLED器件电极透过率、亮度、光谱等性能的影响。实验采用真空蒸镀方法制备了一系列器件,器件结构为Ag/MoO_3/Ag/MoO_3(10nm)/NPB(40nm)/Alq_3(60nm)/LiF(1nm)/Al(150nm)。对比器件的电压-电流密度、电压-亮度、光谱特性等数据,表明Ag/MoO_3/Ag的结构为20/20/10(nm)时,器件性能较好。在驱动电压为11V时,其亮度达到18 421cd/m~2,电流效率为2.45cd/A;且因器件中存在微腔效应,其EL光谱蓝移,半高宽变窄。但考虑到530nm处其电极透过率仅为17%,所以经换算该器件实际发光亮度比ITO电极器件更高。该Ag/MoO_3/Ag叠层阳极制作相对简单,经优化后在顶发射和柔性OLED器件方面将具有一定的应用前景。     

Temperature and flow modulation doping of manganese in ZnS electroluminescent films by low pressure metalorganic chemical vapor deposition

A temperature and flow modulation (TFM) technique has been developed to modulate the manganese doping profile in ZnS phosphor material grown by lowpressure metalorganic chemical vapor deposition for alternating-current thin film electroluminescent devices (TFELDs). In the TFM technique, modulation of both the substrate temperature as well as the flows of metalorganic sources, diethylzinc and tricarbonyl-(methylcyclopentadienyl)-manganese (TCPMn), was used to grow a structure consisting of alternating layers of undoped ZnS at 400°C and Mn-doped ZnS where Mn being incorporated into the undoped ZnS at 550°C. X-ray results indicated that MnS_x phases were present within the ZnS host crystal matrix for the modulation doped samples, while a Mn_xZn_1-xS solid solution was present in the uniformly doped samples. The luminescence efficiency of the TFELDs could be modified by growing the phosphor with dopant (luminescent center) modulation. The TFELDs with a single modulated doping phosphor layer showed lower threshold voltages in the range 70 to 80 V with light emission in the 580 to 587 nm wavelength range. With a twofold increase in the total thickness of the undoped ZnS layer, the brightness and the luminescence efficiency, measured at the threshold voltage plus 40 V, increased by a factor of 20 and 10, respectively. The electroluminescent (EL) characteristics of the phosphors with multiple dopant layers showed higher luminescence efficiency. By using the TFM growth technique, one can engineer the luminescent center distribution in the phosphor layer to improve the EL characteristics.     

EL characteristics of a TFEL/TFT stacked structure display devicedriven by a HV-Si·TFT circuit

TFEL/TFT stacked structure display devices were fabricated onto a quartz substrate. By using a HV-TFT circuit as the basis of a TFEL/TFT device, an EL device on the TFT circuit can be switched at a sufficiently low signal line voltage of V_s=2-3 V. The maximum brightness of the TFEL/TFT device is 230 cd/m² and the ON/OFF brightness ratio is more than 90 between Vs=0 and Vs=4 V at a V_app frequency of 5 kHz and a voltage of 50. Evaluation of the dynamic behavior of TFT circuits using multichannel HV-Si·TFT's showed that the rise time of the fundamental TFT circuit at the EL driving point of the circuit was about 20 μs and that the hold time of the circuit was about 70 mS. The rise time and the fall time of the luminescence were each about 20 μs. The memory characteristics of the TFEL/TFT device showed that the hold time of the luminescence was about 40 mS. These dynamic characteristics of the TFEL/TFT stacked structure device satisfy the conditions required for a flat panel display     

n型聚合物掺杂p型聚合物单层电致发光器件

成功制备了可溶性n型聚合物PPQ掺杂的可溶性p型聚合物PDDOPV的单层发光器件。与具有相同厚度的纯PDDOPV的单层器件相比，起亮电压从4.5V降低到2.6V；在电压相同的条件下，掺杂的单层器件的电流和纯PDDOPV的单层器件在同一个数量级，但亮度和发光效率均高出1个数量级以上。在10V时，掺杂器件与未掺杂器件的电流、亮度和发光效率的比值分别是1.95,30.9和16.0。掺杂器件亮度和发光效率的大幅提高被归因于在PDDOPV中掺杂PPQ降低了少子的注入势垒，提高了少子注入水平。这一结果表明，在可溶性p型聚合物中掺杂可溶性n型聚合物是提高器件性能的有效方法。     

Solution-processable tandem solid-state light-emitting electrochemical cells

Compared to organic light-emitting diodes (OLEDs), solid-state light-emitting electrochemical cells (LECs) exhibit simple single-layered structure and low operating voltages due to in situ electrochemical doped layers. However, device efficiencies of LECs are usually lower than those of sophisticatedly designed OLEDs. Furthermore, device efficiencies and lifetimes of LECs degrade significantly as brightness increases. In this work, we demonstrate tandem LECs to obtain nearly doubled light outputs (μW cm⁻²) in comparison with single-layered LECs under similar current densities. Since the output EL emission is modified by microcavity effect of the device structure, the EL spectra of tandem LECs exhibit EL emission peak at ca. 625 nm while the EL spectra of single-layered LECs center at ca. 660 nm. Better spectral overlap between the EL spectrum of tandem LECs and the luminosity function results in further enhanced candela values, rendering a tripled brightness (cd m⁻²). The device efficiencies can be optimized by adjusting the thickness of the connecting layer between the two emitting units of the tandem devices. The peak external quantum efficiency achieved in tandem LECs is up to 5.83%, which is higher than twice of that obtained in single-layered LECs due to improved carrier balance. When single-layered and tandem LECs are biased under higher voltages to reach similarly higher brightness, tandem LECs show higher device efficiencies and longer lifetimes simultaneously. These results indicate that device efficiencies and lifetimes of LECs can be improved by employing a tandem device structure.     

AlGaN基p-i-n型日盲紫外探测器材料的研制

采用金属有机气相外延(MOCVD)方法在(0001)面蓝宝石衬底上生长了AlN和高铝组分AlGaN材料。通过优化AlN和AlGaN材料的生长温度、生长压力和Ⅴ族元素/Ⅲ族元素物质的量比(nⅤ/Ⅲ)等工艺条件,得到了高质量的AlN和高铝组分AlGaN材料。AlN材料X射线双晶衍射ω(002)半宽为74 arcsec,透射光谱测试带边峰位于205 nm,带边陡峭;Al组分为45%的AlGaN材料X射线双晶衍射ω(002)半宽为223 arcsec,透射光谱测试带边峰位于272 nm,带边陡峭。采用此外延工艺方法生长了AlGaN基p-i-n型日盲紫外探测器材料并进行了器件工艺流片,研制出AlGaN基p-i-n型日盲紫外探测器,响应峰值波长为262 nm,在零偏压下的峰值响应度达到0.117 A/W。     

Submicrometer Comb-Drive Actuators Fabricated on Thin Single Crystalline Silicon Layer

Electrostatic comb-drive microactuators were fabricated by electron beam lithography on a 260-nm-thick silicon layer of a silicon-on-insulator wafer. The actuators consisted of comb electrodes, springs, and a frame. Two kinds of microactuators with doubly clamped and double-folded springs were designed and fabricated. The comb electrode was as small as 2.5 mum wide and 8 mum long and was composed of 250-nm-wide, 260-nm-thick, and 2-mum-long fingers. The air gap between the fingers was 350 nm. The spring was 250 nm wide, 260 nm thick, and 17.5 mum long, and the spring constant was 0.11 N/m. The force and displacement generated by the microactuator were 2.3 x 10^-7N and 1.0 mum, respectively. Applying an ac voltage, the oscillation amplitude became maximum at a frequency of 132 kHz. The mechanical and electrical characteristics of the fabricated actuators were investigated quantitatively.