The theory of Light Emitting Diodes(LEDs) life tests and mathematic model of life tests were introduced. The performance of LEDs was affected by the drive current and by the ambient temperature. Life tests of tunnel junction regenerated AlGaInP LEDs were performed at different currents and ambient temperatures. On axis output intensity of tunnel junction regenerated LED had decreased 35.53% after 5203 hours at 30mA and 25°C. At the ambient temperature of 80°C, on axis output intensity of tunnel junction regenerated LED had degraded 19.26% after 3888 hours at 20mA. According to the results mentioned above, the normal working lifetime of tunnel junction regenerated LEDs were concluded. Moreover, the main Failure Mechanisms of it were described. Our work reviews the failure analysis that was performed on the degraded LEDs and the degradation mechanisms that were identified. The results show a thermal degradation mechanism that dominates degradation at high ambient temperatures.
A Novel structure of dual-wavelength semiconductor laser diode is proposed and fabricated. Two laser structures based on two kinds of materials AlGaAs and AlGaInP active layer, which are cascaded by a high doping tunnel junction during the epitaxial growth. The lasers can emit at wavelength of 699nm and 794nm at the same time. Without face coating, the output power of the dual-wavelength laser is high as 50mW at 220mA. And the slope efficiency of these devices is about 0.42A/W.
A Novel structure of high power dual-wavelength semiconductor laser diode is proposed and fabricated. Two laser structures are cascaded by a high doping tunnel junction during the epitaxial growth. The lasers can emit at wavelength of 951nm and 987nm at the same time. Without facet coating, the output power of the dual-wavelength laser is as high as 3.1W at 3A. And the slope efficiency of these devices is about 1.21A/W. Much higher output power can be reached for those dual-wavelength lasers when modifying the structure. The external differential quantum efficiency of different cavity length devices is analyzed.
Tunnel cascaded and coupled multi-active regions laser diodes are novel high power laser diodes. This kind of laser diodes can achieve high output power at relatively low current density and overcome the main hindrance of the normal high power semiconductor lasers: catastrophic optical damage (COD) by increase the size of facula. Transient thermal property of these laser diodes has been calculated by using finite element method (FEM). Three kinds of laser diode structures, one active region, two active regions with one tunnel junction and three active regions with two tunnel junctions, are simulated. The calculated results are in agreement with the measured data. The result indicates that for tunnel cascaded and coupled multi-active regins laser diodes, temperature rising of the active region near the substrate is a little higher than that near heat sink. With active region number increasing, the temerature of the laser diodes rises but multi-active regions were fabricated on the uniform substrate, its thermal resistance is still smaller than that of series with the same number normal laser diodes.
A new mechanism of tunneling-regenerated multi-active region LEDs with high quantum efficiency and high brightness has been presented. The layer structure, MOCVD growth, device technology, a several of measured curves and their analysis of these new mechanism LEDs were shown in the paper. It was theoretically and experimentally resulted in that efficiency of the electro-luminescence and the on-axis luminous intensity can linearly increase approximately with the number of active regions.
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