Zhanguo Li

High-Efficiency 808-nm InGaAlAs–AlGaAs Double-Quantum-Well Semiconductor Lasers With Asymmetric Waveguide Structures

The InGaAlAs-AlGaAs double-quantum-well semiconductor lasers grown by molecular beam epitaxy show high quantum efficiency and high power conversion efficiency at continuous-wave power output using asymmetric waveguide structures. The threshold current density and slope efficiency of the device are 180 A/cm2 and 1.4 W/A, respectively. The internal loss and the internal quantum efficiency are 1.1 cm-1 and 97%, respectively. The 75% maximum power conversion efficiency is achieved in 100-mum stripe widths 808-nm-emitting laser diodes with 1000-mum cavity length.

2.0 μm room temperature CW operation of InGaAsSb/AlGaAsSb laser with asymmetric waveguide structure

The GaInAsSb/AlGaAsSb double quantum well lasers with an emission wavelength 2.0 μm, using the separate-confinement asymmetric waveguide, have been designed and fabricated, showing high quantum efficiency and high power conversion efficiency at continuous-wave operation mode. The threshold current density of the device is as low as 92 A/cm2. The internal loss coefficient and the internal quantum efficiency are 1.0 cm−1 and 86.1%, respectively. The 35% maximum power conversion efficiency (PCE) and narrow far-field patterned were achieved.

Long wavelength strain-engineered InAs multi-layer stacks quantum dots laser diode on GaAs substrate

The growth of GaAs based 1.5 μm multi-layer stacked InAs quantum dots (QDs) has been investigated by solid-source molecular beam epitaxy (SSMBE), which was very important devices for transmission window. Owing to a strong electronic coupling between the QDs layers and the quantum wells (QWs), and antimony (Sb) introduced by for long-wavelength semiconductor lasers were obtained. The device structure for QDs laser diodes (LDs) with a cavity length of 1000 μm and stripe width of 100 μm as well as the device fabrication results will also be presented. The output performance was achieved with continuous wave (CW) operation, the measurement were from 20 to 60°C with a temperature step of 10°C. The threshold current density was 168 A/cm2, and the CW operating up to 20 mW at room temperature (RT) was achieved.

Study on Surface Passivation Homogeneity of Gallium Antimonide using Photoluminescences

Improvement in optical and surface morphology were observed after sulphur passivation of gallium antimonide surface. The effect of surface passivation of Te-doped n-GaSb by (NH4)2S treatment was investigated by using photoluminescence (PL), Atomic Force Microscope (AFM). The optimum passivation time is around 180 s. Under this condition, the relative PL spectrum intensity of passivated sample can be approximately 10 times stronger than as-grown sample. Meanwhile, the best luminescence homogeneity and suface morphology could be obtained.

Growth and characterization of InAs quantum dots with low-density and long emission wavelength

The growth parameters affecting the deposition of self-assembled InAs quantum dots (QDs) on GaAs substrate by low-pressure metal-organic chemical vapor deposition (MOCVD) are reported. The low-density InAs QDs (~5×10^8 cm^(-2) are achieved using high growth temperature and low InAs coverage. Photoluminescence (PL) measurements show the good optical quality of low-density QDs. At room temperature, the ground state peak wavelength of PL spectrum and full-width at half-maximum (FWHM) are 1361 nm and 23 meV (35 nm), respectively, which are obtained as the GaAs capping layer grown using triethylgallium (TEG) and tertiallybutylarsine (TBA). The PL spectra exhibit three emission peaks at 1361, 1280, and 1204 nm, which correspond to the ground state, the first excited state, and the second excited state of the QDs, respectively.

Optical properties of 1.3-\mum InAs/GaAs quantum dots grown by metal organic chemical vapor deposition

The optical properties of self-assembled InAs quantum dots (QDs) on GaAs substrate grown by metal-organic chemical vapor deposition (MOCVD) are reported. Photoluminescence (PL) measurements prove the good optical quality of InAs QDs, which are achieved using lower growth temperature and higher InAs coverage. At room temperature, the ground state peak wavelength of PL spectrum and full-width at half-maximum (FWHM) are 1305 nm and 30 meV, respectively, which are obtained as the QDs are finally capped with 5-nm In0.06Ga0.94As strain-reducing layer (SRL). The PL spectra exhibit two emission peaks at 1305 and 1198 nm, which correspond to the ground state (GS) and the excited state (ES) of the QDs, respectively.

Effect of InGaAs strain reducing layer and rapid thermal annealing on the properties of InAs/GaAs quantum

In this study, uniform InAs QDs were grown on the GaAs (001) substrate by MBE by the S-K mode. The effects of strain reducing layer and rapid thermal anneling on the optical properties of InAs/(In)GaAs QDs were investigated by PL measurements. The annealing results in PL peak energy red-shift which strongly depends on In composition of InxGaAs strained reducing layer , QDs with lower density and/or capped by an InGaAs layer are very sensitive to the annealing. At given annealing conditions, PL peak energy blue-shift of low-density QDs is much larger than that of high density QDs.

2.2 μm InGaAsSb/AlGaAsSb laser diode under continuous wave operating at room temperature

Abstract2.2 μm InGaAsSb/AlGaAsSb Sb-based type-I laser diodes (LDs) were fabricated, with cavity lengths of 1000 μm and stripe width of 150 μm. The high output performance was achieved with the threshold current density of the device is as low as 187 A/cm2, slope efficiency of 0.2 W/A, and vertical and parallel divergent angles ϑ⊥ = 42° and ϑ| = 10°, respectively. The continuous wave operating up to 320 mW at room temperature (RT) were achieved.

Study on high quality InGaAsSb/AlGaAsSb MQWs grown by molecular beam epitaxy

In this work, the Type I InGaAsSb/AlGaAsSb multiple-quantum-wells (MQWs) has been grown by molecular beam epitaxy (MBE). The comprised five InGaAsSb quantum wells are embedded in AlGaAsSb barriers, the barriers/QWs periodicity matches to GaSb substrates, and satellite peaks indicate a good crystalline quality. The central peak emission wavelength is around 2.0 µm at room temperature by photoluminescence (PL), with a full-width at half-maximum (FWHM) of 39 meV.

Carbon nanotubes and thermal properties

Because of high thermal conductivity, the carbon nanotubes (CNT) present extensive application prospects, particularly in microelectronic, optoelectronic device heat sinks, and semiconductor lasers. In this letter, the single walled carbon nanotubes are prepared with high yield by DC arc discharged with Y/Ni as catalysts. The morphology, diameter distribution and microstructure of the carbon nanotubes are analyzed with transmission electron microscope (TEM) and resonant Raman spectroscopy. The thermal properties of carbon nanotubes are studied. It finds that the tube diameter increases with the temperature rising, and the large tube has the small thermal-sensitivity, suitable for applications as the heat dissipation in device.