AlGaInP visible resonant cavity light-emitting diodes

Visible (670-nm) resonant cavity light-emitting diodes (RCLEDs) composed entirely of AlGaInP alloys are discussed. The devices consist of a strained quantum well optical cavity active region surrounded by AlInP/(AlGa)InP distributed Bragg reflectors (DBRs). The bottom DBR is a 60.5 period high reflector while the top partial reflector, which determines the emission linewidth, is a five-period output coupling DBR with a reflectance of about 57%. The devices exhibit linewidths of 4.8 nm (13.3 meV) at 300 K and are promising for plastic fiber communication systems and monochromatic displays     

GaN resonant cavity light-emitting diodes for plastic optical fiber applications

The optical designs of resonant GaN light-emitting diodes (LEDs) have been determined for maximum extraction efficiency into typical plastic optical fiber of numerical aperture 0.5. An optimum extraction efficiency of 3.9% can be achieved for a practical resonant cavity LED (RCLED), taking account of current growth and processing considerations. The optimized device is a metal-active layer distributed Bragg reflector construction. Constructive interference effects from the top metal mirror are found to play the dominant role in efficiency enhancement. The extraction efficiency of an optimized resonant single-mirror LED is found to be 3.3%, indicating a small compromise in performance compared with the more complex RCLED structure.     

Effect of top distributed Bragg reflectors on the performance of 650 nm AlGaInP resonant cavity light-emitting diodes

Three kinds of 650 nm AlGaInP resonant cavity light-emitting diodes (RCLEDs) are fabricated by metal organic chemical vapor deposition (MOCVD) with different numbers of pairs of top distributed Bragg reflectors (DBRs), which are 15, 10 and 5, respectively. By comparing the full width at half maximum (FWHM), light power and the angular far-field emission of the devices, the device with 15 pairs of top DBRs shows the best performance. Its FWHM is 13.4 nm and the light power is 0.63 mW at a driving...     

AlGaInP microcavity light-emitting diodes at 650 nm on Gesubstrates

We demonstrate microcavity light emitting diodes (MCLEDs) emitting at 650 nm on Ge substrates. Ge has the advantage of lower cost and higher strength compared to GaAs substrates. The multi-quantum well microcavity devices consisted of AlGaAs-based distributed Bragg reflector (DBR) mirrors, AlGaInP active material with an additional 5-μm p-Al_0.55Ga_0.45As current spreading layer on top of the p-DBR. A maximum external quantum efficiency of 4.35% and an optical power higher than 5 mW was obtained for a device with 200-μm diameter. The results indicate the potential use of MCLEDs on Ge for visible LEDs     

High brightness visible (660 nm) resonant-cavity light-emittingdiode

Visible (660 nm) resonant-cavity light-emitting (RCLEDs) have been fabricated. The top-emitting devices employed two AlGaAs-AlAs-Bragg mirrors and GaInP-AlGaInP quantum-well active layers. The device performance was characterized as a function of the device diameters, ranging from 24 to 202 μm. The larger devices exhibited a nearly linear increase of output power with injected current with 8.4-mW emission at 120 mA. A maximum external efficiency of 4.8% was measured at 4 mA on the 84-μm aperture devices. All devices exhibited a narrow emission at 659-661 nm with a linewidth around 3 nm. The results show that RCLED's are promising low-cost light sources for plastic fiber transmission as well as display applications     

High gain resonant cavity enhanced InGaAs/AlGaAs heterojunctionphototransistor resonant at 930 nm

A resonant cavity enhanced InGaAs/AlGaAs phototransistor with high responsivity in the transmission window of the GaAs substrate is reported. The resonant wavelength is 929 nm with a full width at half maximum of 9 nm. The peak responsivity increases from 17 A/W at 0.1 μW incident optical power to 400 A/W at 100 μW     

High-radiance light-emitting diodes

The properties of AlxGa1-xAs heterojunction incoherent edge emitters are described. Single (SH) and double-heterojunction (DH) diodes emitting at about 8200 Å were studied. The highest CW radiance measured perpendicular to the emitting facet was 95 W/cm².sr at 4200 A/cm²for a stripe-geometry SH device. This high radiance level was found to be consistent with an operating life of many thousands of hours. The near- and far-field patterns of the diodes are presented as well as the spectral characteristics and the radiance as a function of drive current, both pulsed and dc.     

Degradation in short wavelength (AlGa)As light-emitting diodes

Degradation in short-wavelength (AlGa)As lasers is investigated through lifetests of such devices operated in the incoherent mode. It is shown that degradation increases with emission energy for diodes containing zinc in the p-type (AlGa)As bounding region, whereas diodes containing Ge in this region, although not satisfactory as c.w. lasers because of high resistivity, show no degradation. A way out of this difficulty is proposed through double doping with Ge and Zn, in which case degradation appears to be brought down to the Ge level.     

Ⅰ类非临界相位匹配LBO腔外倍频660nm效率的研究

报道了利用LBO晶体对Nd:YAG纳秒激光器进行腔外倍频实验的研究结果,实验中LBO晶体采用Ⅰ类非临界相位匹配(NCPM),温度调谐。实验证明,采用LBO温度调谐方式具有倍频效率高、稳定性好、易于调节等优点,当匹配温度为8.4℃、基频光功率为1.3J时,获得了855mJ的660nm倍频光输出,最高转换效率达到66%,倍频光能量稳定度小于±3%。     

Monolithic super-bright red resonant cavity light-emitting diodegrown by solid source molecular beam epitaxy

Monolithic super-bright resonant-cavity light-emitting diode operating at λ=663 nm has been developed. The diode consisted of a 1λ-thick AlGaInP active region sandwiched between AlAs-AlGaAs distributed Bragg reflectors. The device structure was grown by solid source molecular beam epitaxy. The current aperture of the emitter was created by lateral selective wet thermal oxidation. A record-high peak wall-plug efficiency of 2.2% and a continuous-wave output power of 1.4 mW were attained without heatsinking at room temperature from a diode having a diameter of 80 μm. The emission linewidth was as narrow as 4.5 nm     

CMOS-compatible organic light-emitting diodes

We report a new method for the integration of light-emitting devices on a silicon substrate. As an active layer, we use unsubstituted PPV or PPV-based organic macromolecules with a p⁺-silicon anode and a cathode made from aluminum or titanium. The polymer is deposited by spin-coating the precursor, followed by a thermal conversion step to form the macromolecules. All process steps, including the possibility of dry etching of the active layer and the upper electrode, are typical for MOS technology. Spectrum analysis, current-voltage, and intensity measurements have been carried out for device characterization. These organic light-emitting diodes allow the monolithic integration of microelectronic circuits and light-emitting devices on one silicon chip applying only typical MOS process steps     

InGaN microring light-emitting diodes

The fabrication and performance of an InGaN light-emitting diode (LED) array based on a microring device geometry is reported. This design has been adopted in order to increase the surface area for light extraction and to minimize losses due to internal reflections and reabsorption. Electrical characteristics of these devices are similar to those of a conventional large-area LED, while the directed light extraction proves to be superior. In fact, these devices are found to be more efficient when operated at higher currents. This may be attributed to improved heat sinking due to the large surface area to volume ratio. The potential applications of these devices are also discussed.     

基于混合配体Znq(DBM)的单色和白色OLED

以8-羟基喹啉(q)和1,3-二苯基-1,3-丙二酮定向合成了有机小分子配合物Znq(DBM),将其作为发光层制备了单色有机电致发光器件(OLED)。在结构为ITO/m-MTDATA(5nm)/NPB(40nm)/Znq(DBM)(60nm)/LiF(0.5nm)/Al(100nm)的器件中,启亮电压为5V,最大亮度达到4 575cd/m2。同时又在器件中引入间隔层BCP,研究其不同厚度对OLED性能的影响。在结构为ITO/m-MTDATA(5nm)/NPB(40nm)/BCP(x nm)/Znq(DBM)(60nm)/LiF(0.5nm)/Al(100nm)的器件中,当BCP层厚为0nm时,发光颜色为黄绿色;当BCP层厚为1nm时,发光颜色为白色,色坐标为(0.29,0.33),最大亮度为2 231cd/m2;当BCP层厚为5nm时,发光颜色为蓝色。根据器件结构和性能,讨论了其内部机理。     

InP-base resonant tunneling diodes

We have fabricated Ino.53Ga0.47As/AlAs/InP resonant tunneling diodes (RTDs) based on the air-bridge technology by using electron beam lithography processing. The epitaxial layers of the RTD were grown on semiinsulating (100) InP substrates by molecular beam epitaxy. RTDs with a peak current density of 24.6 kA/cm2 and a peak-to-valley current ratio of 8.6 at room temperature have been demonstrated.     

InP基共振遂穿二极管器件（RTD）研究

我们在实验中对InGaAs/AlAs/InP共振遂穿二极管（RTD）材料结构进行了优化设计,并用MBE设备在(100)半绝缘InP单晶片上生长了RTD外延材料。我们采用电子束光刻工艺和空气桥互连技术,制作了InP基RTD器件。并在室温下测试了器件的电学特性：峰值电流密度24.6kA/cm2,峰谷电流比(PVCR)为8.6。     

Resonant-cavity light-emitting diodes operating at 655 nm with ahigh external quantum efficiency and light power

Monolithic resonant cavity light-emitting diodes exhibiting an external quantum efficiency (η_ex) up to 6.5% for 84-μm size devices at a wavelength at 655 nm have been demonstrated. Larger diodes, 150-300 μm in diameter, have the maximum η_ex between 5.5% and 4.9% and launch power output up to 8 mW     

InP-based cylindrical microcavity light-emitting diodes

We have investigated the properties of InP-based microcavity light-emitting diodes (λ=1.6 μm). Our objective was mainly to study the effects of lateral confinement of optical modes, which was achieved by the wet oxidation of double In_0.52Al_0.48 As layers. The smallest devices had a cavity radius of 0.5 μm, which becomes comparable to λ/n, where n is the effective refractive index of the photon emitting heterostructure. Two types of devices were tested: the first without any mirrors in the vertical direction, and the second with a combination of MgF/ZnSe DBR (top) and silver (bottom) to produce a low Q~35-45. The latter type of devices exhibited higher output power and narrower spectral linewidth; otherwise, the characteristics were very similar The output slope efficiency monotonically decreases with reduction of lateral cavity size up to ~2-μm in diameter and then is enhanced again for smaller cavity sizes. The slope efficiency of the smallest device (aperture diameter 1 μm) is almost equal to that measured for the largest devices. The maximum output power measured from the devices is 30 μW. The far-field pattern of devices with aperture radii ranging from 1.5 to 20 μm shows an angular width (FWHM) of 50°. On the other hand, devices with smaller aperture (radius ~0.5 μm) exhibit an angular width of 20°. The measured small-signal modulation bandwidth increases from ~0.45 GHz for the larger devices to 0.8 GHz for the smallest devices. Our results indicate that microcavity effects can be observed with only lateral photon confinement, making device fabrication requirements less stringent compared to surface-emitting lasers     

Response times of light-emitting diodes

Response times of light emission from a GaAs0.6P0.4electroluminescent diode have been measured for stepwise applications of voltage. Turn-on times decrease either with an increase of the steady-state level of current or with superposition of a dc bias voltage. The main features of the experiment are in reasonable agreement with those of the calculated curves based on an equivalent circuit with a depletion-layer capacitance and a voltage-dependent diode conductance.     

AlGaInP-sapphire glue bonded light-emitting diodes

A novel method was proposed to glue an AlGaInP-GaAs light-emitting diode (LED) onto a transparent sapphire substrate. The absorbing GaAs was subsequently removed by selective wet etching. It was found that the emission efficiency could reach 401 m/W under 20-mA current injection for the 622-nm glue bonded (GB) AlGaInP-sapphire LED. It was also found that these GB LEDs are highly reliable, with small variations in operation voltage and luminescence intensity during the life test.