Jinyu Du

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.

The reduction of base resistance of SiGe/Si HBT via ion implantation and side-wall oxide self-aligned technique

Ion implantation and the side-wall oxide self-aligned technique was used to reduce the extrinsic base resistance of a SiGe HBT. The sheet resistance of the SiGe layer was reduced over 20 times under proper implantation and annealing parameters, and ohmic contacting was also improved. This can greatly enhance the frequency performance and reduce the noise figure of SiGe HBT. The SiGe sheet resistance is sensitive to the implantation and annealing parameters. For our samples an implantation dose of 10/sup 16//cm/sup 3/ and energy of 35 kev, annealing temperature from 960/spl deg/C to 1000/spl deg/C is suitable.

Simulation of the high frequency performances of a new type of SiGe HBT and fabrication

In this paper, a new type of SiGe HBT with modulation doped quantum well base structures has been presented for the first time. It is of both higher cut off frequency f/sub T/ and maximum oscillation frequency f/sub max/ than the current SiGe HBTs. Its high frequency performances have been analyzed and simulated from the physical model, including the influence of the following factors. They are (1) the carrier transport in the undoped quantum well, (2) the parasitic parameters of quantum well and barrier and (3) the carrier transport time from the emitter to collector, as the base width is several hundred angstroms. The results of simulation are in good agreement with those of experimental tests.

High-quality carbon-doped GaAs/AlGaAs material growth in MOCVD and its application for optoelectronic devices

Liquid carbon tetrachloride (CCl4) was used as dopants for the growth of p-type GaAs and AlGaAs materials by low pressure metalorganic chemical vapor phase deposition. Heavily carbon doped (1.9 X 1020 cm-3) GaAs and high quality p-type Al0.3Ga0.7As materials were obtained. Several key growth parameters, such as growth temperature (560 degree(s)C - 725 degree(s)C), V/III ration (20 - 150) and CCl4 molecular flow (10-7 mol/min- 10-5 mol/min), were changed to investigate their influence on doping efficiency, growth rate and material properties. Electrochemistry capacity-voltage, Hall effect and photoluminescence methods were adopted to measure the electrical and optical properties. X ray double crystal diffraction method was used to study the relationships of carbon doping level and crystal lattice constant of epitaxial layers. On the basis of these research, carbon doped GaAs tunnel diode and high power GaAs/AlGaAs/InGaAs strain quantum well semiconductor laser structures were grown to qualify the carbon doped GaAs/AlGaAs materials comprehensively.

Carbon-doped 980-nm InGaAs strained quantum well lasers grown by metalorganic chemical vapor deposition

Graded-index separate-confinement strained quantum well InGaAs/GaAs/GaAlAs lasers grown by metalorganic chemical- vapor deposition with carbon tetrachloride used as p-doped source for upper cladding layer and the capping layer are studied. By SIMS and electrochemical capacitance-voltage measurements, the desirable quantum well structure and the suitable doping and carrier concentrations profiles are found to be obtained. The grown crystals show good optical characteristics through the photoluminescence spectrum measurement of the upper cladding layer and the active layer. The oxide-stripe and the ridge waveguide stripe lasers are fabricated, the lower threshold current densities 160 A/cm2 (uncoated) with 1500 micrometers long cavity are obtained. The differential quantum efficiency and the output power can be up to 0.4 W/A and 500 mw (uncoated).