To investigate the high performance light source for high-speed plastic optical fiber (POF) communication application is important as high-speed short distance communication for the home networks becomes popular. It is straightforward to reduce the size of RCLEDs to increase the small-signal modulation bandwidth (f-3dB). But reduce the size of RCLEDs not only reduce the output power but also decrease lifetime because higher current density flowed through active region. In this paper, we improve. f-3dB of RCLEDs with the aperture of 84μm by reducing the number of quantum wells (QWs) in active region. We found the speed of RCLED inverse proportional to the number of QWs. By reducing the number of QWs to one, the device with standard aperture size exhibits high f-3dB as 235MHz at bias current of 20mA without sacrificing the other performance like maximum output power, high temperature performance, etc. These devices can transmit data rate as high as 500Mb/sec through graded-index POF over 50 meters. Beyond 1Gbits/sec, we have investigated red VCSELs as suitable high-speed light sources. The structure of red VCSELs is similar to RCLEDs except more pairs of DBR yield high reflectivity. Our red VCSEL can have output power as high as 1.5mW at 5mA and transmission data rate up to 2.5Gbits/sec.
We have remarkably improved the Metal Bonding (MB) AlGaInP LED luminous efficiency in the dominant wavelength range form 570 nm to 630 nm. Micro Shaping technology is fabricated on the Surface of LED Chip in order to enhance the extraction efficiency. As a result, the luminous efficiency of the new micro shaping Structure AlGaInP LED can achieve 80 lm/w, at 615 nm dominant wavelength under 20mA injection current. The luminous efficiency increased up to 50% than report valve before.
A high brightness AlGaInP LED with a high reflectivity metal reflector structure was proposed. The AlGaInP LED layers with metal reflector is bonded to the high thermal conductivity silicon substrate by using indium as a solder. Because the light that would otherwise be absorbed by the opaque GaAs substrate is reflected by the high reflectivity metal reflector, the brightness is significantly improved. The high current operating characteristics are also improved by replacing the GaAs substrate with silicon substrate. The luminous efficiency of the new structure AlGaInP LED can achieve more than 40 lm/W in the dominant wavelength range from 585nm to 625nm.
Future in-house Multimedia networks, based on the IEEE 1394b standards, require low cost and robust optical
transmission system in the range of 100 meter. In this paper, we presented the state of the art 650 nm micro-cavity light
emitting diodes (RCLEDs) for such application. We had made RCLEDs with diameters of the emission window of 84, 60, 40μm for different requirements. Because of excellent epitaxy quality and structure design. Our RCLEDs perform record high power and efficiency. With expoxy encapsulated, the 84μm devices give an efficiency of 12% and yield more than 3.5mW at operation current 20mA. Our 40μm devices exhibit high small-signal modulation-bandwidths (f-3D) as 310MHz at bias current of 20mA. The output power of 40μm devices is still as high as 1.5mW, which is suitable for IEEE 1394b s400 standard. On the other hand, we had developed metal bonding RCLEDs (MBRCLEDs) to improve the high temperature performance of RCLEDs. By proper design the structure and process, the MBRCLEDs can have very low power decay as 0.6dB from 20°C to 100°C.
Semiconductor light emitting diode (LED) has become a promising device for general-purpose illumination applications. LED has the features of excellent durability, long operation life, low power consumption, no mercury containing and potentially high efficiency. Several white LED technologies appear capable of meeting the technical requirements of illumination. In this paper we present a new multi-color white (MCW) LED as a high luminous efficacy, high color rendering index and low cost white illuminator. The device consists of two LED chips, one is AlInGaN LED for emitting shorter visible spectra, another is AlInGaP LED for emitting longer visible spectra. At least one chip in the MCW-LED has two or more transition energy levels used for emitting two or more colored lights. The multiple colored lights generated from the MCW-LED can be mixed into a full-spectral white light. Besides, there is no phosphors conversion layer used in the MCW-LED structure. Therefore, its color rendering property and illumination efficiency are excellent. The Correlated Color Temperature (CCT) of the MCW-LED may range from 2,500 K to over 10,000 K. The theoretical General Color Rendering Index (Ra) could be as high as 94, which is close to the incandescent and halogen sources, while the Ra of binary complementary white (BCW) LED is about 30 ~ 45. Moreover, compared to the expensive ternary RGB (Red AlInGaP + Green AlInGaN + Blue AlInGaN) white LED sources, the MCW-LED uses only one AlInGaN chip in combination with one cheap AlInGaP chip, to form a low cost, high luminous performance white light source. The MCW-LED is an ideal light source for general-purpose illumination applications.
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