共查询到19条相似文献,搜索用时 125 毫秒
1.
2.
3.
InGaN/GaN MQW双波长LED的MOCVD生长 总被引:1,自引:0,他引:1
利用金属有机物化学气相淀积(MOCVD)系统生长了InGaN/GaN多量子阱双波长发光二极管(LED).发现在20 mA正向注入电流下空穴很难输运过蓝光和绿光量子阱间的垒层,这是混合量子阱有源区获得双波长发光的主要障碍.通过掺入一定量的In来降低蓝光和绿光量子阱之间的垒层的势垒高度,增加注入到离p-GaN层较远的绿光有源区的空穴浓度,从而改变蓝光和绿光发光峰的强度比.研究了蓝光和绿光量子阱间垒层In组分对双波长LED的发光性质的影响.此外,研究了双波长LED发光特性随注入电流的变化. 相似文献
4.
对氮化镓(InGaN/GaN)型MQW(多量子阱)结构的蓝宝石衬底LED(发光二极管)受自发和压电极化效应的影响进行了研究。为了分析LED的输出特性,利用MATLAB软件对传统水平结构的InGaN/GaN型MQW蓝光LED芯片进行了模拟。研究表明,LED各个界面极化电荷同比例增加能稍微改善LED的电学特性,但却显著降低了LED的光输出功率和内量子效率,这主要是由于界面电荷改变了能带结构,阻碍了空穴的扩散与漂移,降低了辐射复合系数。可以通过改变位错密度来降低极化电荷对LED的影响,改善LED的性能。 相似文献
5.
传统的ABC模型主要用于研究InGaN量子阱中载流子的复合动态过程.使用传统的ABC模型计算载流子的复合速率和复合寿命,研究不同发光波长InGaN基LED的3 dB调制带宽与载流子复合机制的关系.计算分析结果表明,在相同的注入电流下,随着有效有源区厚度和量子阱层厚度的减小,400 nm近紫外、455 nm蓝光以及525 nm绿光三种发光波长LED的3 dB调制带宽均明显增大;在100 A/cm2的注入电流密度下,400,455,525 nm三种发光波长LED的3 dB调制带宽分别为62,88,376 MHz;在相同的电流密度下,LED的3 dB调制带宽随着In组分(In元素的原子数分数占In元素与Ga元素的原子数分数总和的比)的增加而增大;由于525 nm波长LED的In组分高,有效有源区厚度薄,所以源区载流子浓度高,在大电流密度下525 nm绿光LED的3 dB调制带宽达到376 MHz. 相似文献
6.
7.
8.
为了进一步提升蓝光激光器的性能,基于实验样品结构,详细研究了不同结构的p型波导层和有源区的组合对InGaN基边发射蓝光激光器性能的影响。利用PICS3D软件模拟计算其光输出功率-电流-电压特性曲线、能带结构、载流子电流密度分布、激射复合率等光电特性。结果表明,In组分渐变的p型波导层和前两个量子垒层、最后一个量子垒层使用AlGaN材料的新结构,可以很好地抑制电子泄漏,增加空穴注入,提高受激辐射复合率,从而提升蓝光激光器的发光效率。在1.5 A注入电流下,新结构的光输出功率可达2.69 W,相较标准结构提升了47.8%。 相似文献
9.
10.
11.
《Electron Devices, IEEE Transactions on》1983,30(4):316-320
Output power saturation in 1.3-µm InGaAsP light emitting diodes with various active layer thickness has been investigated experimentally in a wide temperature range. Nonradiative recombination current with strong injected carrier density dependence, which is responsible for saturation, was found to be proportional to active layer thickness and almost independent of temperature under constant injected carrier density conditions. External quantum efficiency at a constant injected carrier density was found to be independent of active layer thickness. These results indicate strongly that Auger recombination is the dominant nonradiative process in InGaAsP light sources. 相似文献
12.
13.
N. I. Bochkareva V. V. Voronenkov R. I. Gorbunov A. S. Zubrilov P. E. Latyshev Yu. S. Lelikov Yu. T. Rebane A. I. Tsyuk Yu. G. Shreter 《Semiconductors》2012,46(8):1032-1039
The mechanism of the internal quantum efficiency droop in InGaN/GaN structures with multiple quantum wells at current densities of up to 40 A cm?2 in high-power light-emitting diodes is analyzed. It is shown that there exists a correlation between the efficiency droop and the broadening of the high-energy edge of the emission spectrum with increasing current density. It is also demonstrated that the efficiency is a spectrum-dependent quantity and the emission of higher energy photons starts to decrease at higher current densities. The effect of tunneling and thermally activated mechanisms of thermalization of carriers captured into shallow band-tail states in the energy gap of InGaN on the efficiency and the emission spectrum??s shape is considered. Analysis of the results obtained suggests that the efficiency droop occurs at high current densities because of the relative rise in the contribution from nonradiative recombination via defect states as a result of the increasing occupancy of deep band-tail states in InGaN. It is shown that power efficiency close to the theoretical limit can be obtained in the case of low-voltage tunnel injection into localized band-tail states in the InGaN active region. 相似文献
14.
Sh.M. Eladl 《Microelectronics Journal》2008,39(12):1649-1653
In this paper, the effect of interface recombination and self-absorption within the light emitting diode (LED) active region on the efficiency of QWIP-HBT-LED integrated device is considered. This device is composed of a quantum well infrared photodetector (QWIP), a heterojunction bipolar transistor (HBT) and an LED. The evaluation is based on solving the continuity equation describing the carrier diffusion within the LED active region. Analytical expression describing the effect of self-absorption and surface recombination on the LED quantum efficiency is derived. In addition, the active region width and all interested device parameters are involved. It is observed that the quantum conversion efficiency of the device under consideration is degraded by the self-absorption and interface recombination within the recombined region of the LED. Also, the quantum conversion efficiency of the device is increased with the increase of the LED active region as long as the recombination velocity is above a specified value, while it is decreased with the increase of the LED active region as long as the recombination velocity is below this specified value. 相似文献
15.
大功率LED效率特性分析与驱动方案设计 总被引:1,自引:0,他引:1
考察了大功率LED量子效率衰落问题的研究进展并检测和比较了当前市场不同产品的大功率LED性能,随着LED效率-电流特性的逐渐改善,其最高效率所对应驱动电流开始超过额定电流。由此提出LED的矩形波脉冲驱动策略,驱动电路中MOS晶体管栅极由低频(200~800Hz)矩形脉冲调制高频(~40kHz)脉冲产生的间歇式PWM脉冲串来控制,在输出端滤除高频成分后得到接近于矩形波的低频脉冲电流输出。在调节驱动电路的电流工作点以达到负载LED最高发光效率工作点同时,约束输出脉冲峰值电流与占空比以保证LED驱动电流的平均值恒定。 相似文献
16.
Santanu Pradhan Mariona Dalmases Ayse‐Bilgehan Baspinar Gerasimos Konstantatos 《Advanced functional materials》2020,30(39)
Unbalanced charge injection is deleterious for the performance of colloidal quantum dot (CQD) light‐emitting diodes (LEDs) as it deteriorates the quantum efficiency, brightness, and operational lifetime. CQD LEDs emitting in the infrared have previously achieved high quantum efficiencies but only when driven to emit in the low‐radiance regime. At higher radiance levels, required for practical applications, the efficiency decreased dramatically in view of the notorious efficiency droop. Here, a novel methodology is reported to regulate charge supply in multinary bandgap CQD composites that facilitates improved charge balance. The current approach is based on engineering the energetic potential landscape at the supra‐nanocrystalline level that has allowed to report short‐wave infrared PbS CQD LEDs with record‐high external quantum efficiency in excess of 8%, most importantly, at a radiance level of ≈5 W sr?1 m2, an order of magnitude higher than prior reports. Furthermore, the balanced charge injection and Auger recombination reduction has led to unprecedentedly high operational stability with radiance half‐life of 26 068 h at a radiance of 1 W sr?1 m?2. 相似文献
17.
D. A. Firsov L. Shterengas G. Kipshidze V. L. Zerova T. Hosoda P. Thumrongsilapa L. E. Vorobjev G. Belenky 《Semiconductors》2010,44(1):50-58
The dynamics of interband photoluminescence has been studied at various temperatures and excitation levels in structures with
quantum wells based on InGaAsSb alloys and barriers based on AlGaAsSb and AlInGaAsSb alloys. The lifetimes of optically injected
charge carriers in quantum wells at various temperatures and levels of optical excitation have been experimentally determined.
An increase in the recombination rate in structures with deeper InGaAsSb/AlGaAsSb quantum wells for electrons is attributed
to manifestation of resonant Auger recombination. The Auger recombination brings about heating of electrons and holes in lower
subbands of dimensional quantization. The temperature of charge carriers in the course of Auger recombination is estimated
using the equation for balance of power with accumulation of nonequilibrium optical phonons taken into account. The studied
structures were used to fabricate lasers of two types with lasing wavelength of approximately 3 μm; it is shown that the use
of a quinary alloy as the material for the barrier leads to an improvement in the characteristics of the lasers. 相似文献
18.
Point defects in GaN and, in particular, their manifestation in the photoluminescence, optical absorption, and recombination current in light-emitting diodes with InGaN/GaN quantum wells are analyzed. The results of this analysis demonstrate that the wide tail of defect states in the band gap of GaN facilitates the trap-assisted tunneling of thermally activated carriers into the quantum well, but simultaneously leads to a decrease in the nonradiative-recombination lifetime and to an efficiency droop as the quasi-Fermi levels intersect the defect states with increasing forward bias. The results reveal the dominant role of hydrogen in the recombination activity of defects with dangling bonds and in the efficiency of GaN-based devices. 相似文献
19.
The dependences of the quantum efficiency of InGaN/GaN multiple quantum well light-emitting diodes on the temperature and excitation level are studied. The experiment is performed for two luminescence excitation modes. A comparison of the results obtained during photo- and electroluminescence shows an additional (to the loss associated with Auger recombination) low-temperature loss in the high-density current region. This causes inversion of the temperature dependence of the quantum efficiency at temperatures lower than 220–300 K. Analysis shows that the loss is associated with electron leakage from the light-emitting-diode active region. The experimental data are explained using the ballistic-overflow model. The simulation results are in qualitative agreement with the experimental dependences of the quantum efficiency on temperature and current density. 相似文献