Guo Gao

Tunnel-regenerated multiple-active-region light-emitting diodes with high efficiency

Tunnel-regenerated multiple-active-region (TRMAR) light-emitting diodes (LEDs) with high quantum efficiency and high brightness have been proposed and fabricated. We have proved experimentally that the efficiency of the electrical luminescence and the on-axis luminous intensity of such TRMAR LEDs scaled linearly approximately with the number of the active regions. The on-axis luminous intensity of such TRMAR LEDs with only 3 mum GaP current spreading layer have exceeded 5 cd at 20 mA dc operation under 15 degrees package. The high-quantum-efficiency and high-brightness LEDs under the low injection level were realized

Current-voltage characteristics of p-GaAs∕n-GaN heterojunction fabricated by wafer bonding

p-GaAs∕n-GaN heterojunction was fabricated by wafer bonding. Its current-voltage characteristic was systematically investigated at room temperature and at a variety of low temperature. The curves of different temperatures in the logarithmic scales indicate space-charge-limited currents (SCLCs) in the high voltage region (>0.4V). SCLC current-transport mechanism was confirmed by fitting data. Single-charge injection and the amorphous layer at the bonding interface are presumably the reasons to cause SCLCs.

Novel large-coupled optical cavity semiconductor lasers and multiactive region light-emitting diodes with high performance

Novel multi-active region semiconductor lasers with large coupled optical cavity and high quantum efficiency, and new mechanism tunneling-regenerated multi-active region light emitting diodes with high quantum efficiency and high brightness have been proposed and fabricated. The external and differential quantum efficiency are 2.9 and 3.0 W/A, and the output light power as high as approximately 5 W when the injecting current equals 2A for the four active region 980 nm strained InGaAs/GaAs QW lasers. The fundamental mode light output with perpendicular angle <EQ 17 degrees for this type of large coupled optical cavity laser has been achieved. The on-axis luminous intensity of the new mechanism 620 nm AlGaInP/AlInP LEDs with two active regions is more than 5 cd. It was theoretically and experimentally resulted in that the electro-luminescence efficiency and the on-axis luminous intensity are linearly increasing approximately with the number of the active regions.

High-power coupled large-cavity lasers and multiactive light-emitting diodes

For increasing laser diode (LD) output power, improving laser beam quality and enhancing the light emitting diode (LED) brightness, the coupled large optical cavity semiconductor lasers and multi-active LEDs with tunneling- regenerated current transport have been presented and experimented. Both the external and differential quantum efficiency and both the LDs output power and LEDs brightness are together increasing approximately with the number of the active regions. The very high power Lds and and the very high brightness LEDs working the low injecting current and also the fundamental mode stimulated light with good beam quality have been achieved in our laboratory.

High efficiency tunneling-regenerated multi-active region light-emitting 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.

The resistance characteristics of the Ni-Cr thin films and their influence on the integrated circuits

Ni-Cr thin films with different thicknesses have been fabricated on the dielectric substrate silicon dioxide (SiO/sub 2/) by using magnetron sputtering and vacuum evaporation and annealed at different temperatures. The sheet resistance and the strip line microwave impedance of the Ni-Cr thin film are measured. The results show that they are influenced strongly by the thickness and the annealing temperature. These problems are analyzed in detail including the effects of the carrier tunnel transport, the oxidation, the condensation and the stabilization in the thin film.

The reliability of tunnel junction regenerated light emitting diodes

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.

Thermal property of tunnel-regenerated multiactive-region light-emitting diodes

The thermal property of tunnel-regenerated multiactive-region (TRMAR) light-emitting diodes (LEDs) is studied in detail in this letter. These devices have the advantages of high quantum efficiency and high output optical power. To obtain the same output optical power, it has been shown that the thermal performance for TRMAR LEDs is much better than that of conventional ones. The heat generated from the reverse-biased tunneling junction in TRMAR LEDs is small and can be neglected as compared with heat produced from the active region as illustrated in scanning thermal microscopy result. An experimental comparison shows that the improved input power dependence on the luminescence intensity proves that TRMAR LEDs have better thermal properties than those of conventional ones.

Thermal analysis of InGaAs/AlGaAs quantum well lasers diode by atomic force microscope (AFM)

In this paper, a 4 /spl mu/m ridge waveguide 980 nm InGaAs/AlGaAs quantum well laser diode is fabricated. It shows excellent optical and electrical characteristics. The output power is 68 mW with a threshold current of 35 mA. The far-field pattern shows fundamental transverse mode operation. Thermal properties of the diodes are presented by atomic force microscope (AFM) images. They clearly show the filling layer of SiO/sub 2/ near the ridge and that the active layer is the more thermal area in the cavity surface. The optical and electrical properties of 100 /spl mu/m wide stripe laser diodes are studied and thermal analysis is performed through the threshold current density at different operation temperatures.

Tunneling regenerated high-power dual-wavelength laser diodes

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.