A structure for high brightness light-emitting diodes (LEDs) is demonstrated. A distributed Bragg reflector (DBR) is used to enhance the quantum efficiency of the LEDs. This unique DBR uses a composite structure that consists of two DBRs to provide both high reflectivity and wide angle reflection. For 590 nm (amber range) AlGaInP LEDs, the quantum efficiency is increased to 5.05% by using this composite DBR structure. This result is much better than those obtained from conventional DBRs, and is comparable to that of wafer bonded AlGaInP LEDs.

We have successfully developed a selective surface coating technique to control the modal behavior of the ion-implanted vertical-cavity surface-emitting laser (VCSEL). With selective deposition of a germanium coating by the lift-off process, we could spatially control the threshold gain condition of the VCSEL to support the single transverse mode. The threshold current is 7 mA and single transverse mode operation is maintained up to 1 mW. The method is simple and nondestructive compared with other techniques.

A new and improved method of growing Al-free GaInP/GaAs quantum wells (QWs) is presented. We found that both interfaces are important for obtaining a high-quality quantum well. With an added H purge and PH pre#ow procedure, we have signi"cantly improved the GaInP on GaAs interface by eliminating the unwanted dark line region at the interface. At the GaAs on GaInP interface, we added a thin GaAsP layer. This layer e!ectively prevents the In memory e!ect at the interface. As a result of this new growth procedure, a linewidth of 6.7 meV (at 20 K) for the quantum well emission was achieved.

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 o f 8 4 µ m b y r e d u c i n g t h e n u m b e r o f q u a n t u m w e l l s (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.

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