Deshu Zou

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

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.

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.

Optoelectronic transport mechanism from subband infrared absorption and tunneling regeneration

The main problems of conventional multi-quantum well infrared photodetectors (QWIPs) were discussed. In order to overcome the limitations of the conventional QWIPs, such as small photocurrent, high dark current and low response speed, novel QWIPs in which photocurrent increases with the number of well were proposed. The novel structure with several wells were calculated and analyzed in detail, and successfully fabricated. The dark current lower than conventional QWIPs by about one order of magnitude was obtained, well in agreement with theoretical value. I–V characteristics of the novel QWIPs with six wells has been presented, and six related negative differential resistance regions were observed at positive bias. The absorption photocurrents of the novel QWIPs at 77 K were found to increase with well numbers, confirming the mechanism of the new structure. Furthermore, the transportation of the optoelectronic and some other problems of the QWIPs were discussed.

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.

Performance of 650 nm AlGaInP RCLEDs with different p-type DBRs

Resonant cavity light-emitting diodes (RCLEDs) which composed of active region surrounded by two distributed Bragg reflector (DBR) mirrors have been reported in the communication system based on Plastic Optical Fiber (POF) and high brightness application. However, high performance of 650nm AlGaInP RCLED, which is strongly depends on the optimization of DBRs, especially the matched reflectivity between p-type and n-type DBR mirrors, is still difficult to obtain. In this paper, the performance of 650nm RCLEDs including 34-pair AlGaAs/AlAs n-type DBRs and different pairs of AlGaInP/AlInP p-type DBRs have been investigated both theoretically and experimentally. Top emitting chips with the size of 225×225µm2 without encapsulation were fabricated under the same conditions, experimental results reveal that the device of optimized DBR mirrors with 10-pair p-type DBRs obtain high efficiency, low turn-on voltage and forward resistance, good temperature stability.

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.