Ya-Hsien Chang

1.3-/spl mu/m InAs-InGaAs quantum-dot vertical-cavity surface-emitting laser with fully doped DBRs grown by MBE

We report InAs-InGaAs quantum-dot vertical-cavity surface-emitting lasers (VCSELs) grown by molecular beam epitaxy with fully doped n- and p-doped AlGaAs distributed Bragg reflectors and including an AlAs layer to form a current and waveguiding aperture. The metal contacts are deposited on a topmost p/sup +/-GaAs contact layer and on the bottom surface of the n/sup +/-GaAs substrate. This conventional selectively oxidized top-emitting device configuration avoids the added complexity of fabricating intracavity or coplanar ohmic contacts. The VCSELs operate continuous-wave at room temperature with peak output powers of 0.33 mW and differential slope efficiencies up to 0.23 W/A. The peak lasing wavelengths are near 1.275 /spl mu/m, with a sidemode suppression ratio of 28 dB.

Characterization of InGaN/GaN Multiple Quantum Well Nanorods Fabricated by Plasma Etching with Self-Assembled Nickel Metal Nanomasks

High-density (3.0×1010 cm-2) InGaN/GaN multiple quantum well (MQW) nanorods were fabricated from an as-grown bulk light-emitting diode structure by inductively coupled plasma dry etching with self-assembled nickel metal nanomasks. The self-assembled nickel metal nanomasks were formed by rapid thermal annealing of a nickel metal film at 850°C for 1 min. The influence of the thicknesses of the Ni metal film on the dimensions and density of the nanorods was also investigated. The structural and optical properties of the InGaN/GaN MQW nanorods were established using field emission scanning electron microscopy, transmission electron microscopy and photoluminescence measurements. The diameters and heights of nanorods were estimated to be 60 to 100 nm and more than 0.28 µm, respectively. The peak emission wavelength of the nanorods showed a blue shift of 5.1 nm from that of the as-grown bulk. An enhancement by a factor of 5 in photoluminescence intensity of the nanorods compared with that of the as-grown bulk was observed. The blue shift is attributed to strain relaxation in the wells after dry etching, the quantum confinement effect, or a combination of the two, which results in the enhancement of emission intensity.

Single-mode 1.27-/spl mu/m InGaAs:Sb-GaAs-GaAsP quantum well vertical cavity surface emitting lasers

The 1.27-/spl mu/m InGaAs:Sb-GaAs-GaAsP vertical cavity surface emitting lasers (VCSELs) were grown by metalorganic chemical vapor deposition and exhibited excellent performance and temperature stability. The threshold current varies from 1.8 to 1.1 mA and the slope efficiency falls less than /spl sim/35% from 0.17 to 0.11 mW/mA as the temperature is raised from room temperature to 75/spl deg/C. The VCSELs continuously operate up to 105/spl deg/C with a slope efficiency of 0.023 mW/mA. With a bias current of only 5 mA, the 3-dB modulation frequency response was measured to be 8.36 GHz, which is appropriate for 10-Gb/s operation. The maximal bandwidth is estimated to be 10.7 GHz with modulation current efficiency factor of /spl sim/5.25GHz/(mA)/sup 1/2/. These VCSELs also demonstrate high-speed modulation up to 10 Gb/s from 25/spl deg/C to 70/spl deg/C. We also accumulated life test data up to 1000 h at 70/spl deg/C/10 mA.

Characteristics of InGaAs Submonolayer Quantum-Dot and InAs Quantum-Dot Photonic-Crystal Vertical-Cavity Surface-Emitting Lasers

We have made InGaAs submonolayer (SML) quantum-dot (QD) and InAs QD photonic-crystal vertical-cavity surface-emitting lasers (PhC-VCSELs) for fiber-optic communications in the 990 and 1300 nm ranges, respectively. The active region of the InGaAs SML QD PhC-VCSEL contains three InGaAs SML QD layers, with each of the SML QD layer formed by alternating depositions of InAs and GaAs. The active region of the InAs QD PhC-VCSEL contains 17 undoped InAs-InGaAs QD layers. Both types of QD PhC-VCSELs exhibit single-mode characteristics throughout the current range, with side-mode suppression ratio (SMSR) larger than 35 dB. A maximum output power of 5.7 mW has been achieved for the InGaAs SML QD PhC-VCSEL. The near-field image study of the QD PhC-VCSELs indicates that the laser beam is well confined by the photonic-crystal structure of the device.

Fabrication and Characteristics of high-speed oxide-confined VCSELs using InGaAsP-InGaP strain-compensated MQWs

This paper presents the fabrication and characteristics of high-performance 850-nm InGaAsP-InGaP strain-compensated multiple-quantum-well (MQW) vertical-cavity surface-emitting lasers (VCSELs). The InGaAsP-InGaP MQWs composition was optimized through theoretical calculations, and the growth condition was optimized using photoluminescence. These VCSELs exhibit superior performance with characteristics threshold currents /spl sim/0.4 mA and slope efficiencies /spl sim/0.6 mW/mA. The threshold current change with temperature is less than 0.2 mA, and the slope efficiency drops less than /spl sim/30% when the substrate temperature is raised from room temperature to 85/spl deg/C. A high modulation bandwidth of 14.5 GHz and a modulation current efficiency factor of 11.6 GHz/(mA)/sup 1/2/ are demonstrated. The authors have accumulated life test data up to 1000 h at 70/spl deg/C/8 mA.

Improved photoluminescence of 1.26μm InGaAs∕GaAs quantum wells assisted by Sb surfactant and indium-graded intermediate layers

We have grown high-quality InGaAs∕GaAs quantum wells (QWs) with emission wavelength range of 1.2–1.26μm by metalorganic chemical vapor depositions. By incorporating Sb surfactant and the indium-graded intermediate layers into InGaAs∕GaAs QWs, the photoluminescence (PL) intensity of the 1.26-μm In0.45Ga0.55As∕GaAs QW is enhanced by a factor of 20 and the full width at half maximum value is reduced from 60.4meVto35.9meV. The good crystalline quality is proved by temperature-dependent PL, which shows that the activation energies of In0.45Ga0.55As and Sb-assisted indium-graded In0.45Ga0.55As QWs are 20.87meV and 27.09meV.

10 Gb/s single-mode vertical-cavity surface-emitting laser with large aperture and oxygen implantation

High-speed single transverse mode 850 nm vertical cavity surface emitting lasers (VCSELs) with large emission aperture with a diameter of 8 µm were fabricated. These VCSELs exhibit good performance with threshold currents of 1.5 mA, a single transverse mode emission within the full operational range and a maximum output power of 3.8 mW. The large aperture is advantageous to these VCSELs with a smaller dynamic resistance (60 Ω) than that of conventional single-mode VCSEL. These single-mode VCSELs also demonstrate superior high-speed performance up to 10 Gb s−1.

Performance of 850 nm AlGaAs/GaAs implanted VCSELs utilizing silicon implantation induced disordering

Abstract In this paper, we report a novel implanted vertical surface emitting lasers (VCSELs) utilizing silicon implantation induced disordering. The VCSELs exhibit kink-free current–light output performance with threshold currents ∼2.4 mA, and the slope efficiencies ∼0.45 W/A. The threshold current change with temperature is minimal and the slope efficiency drops less than ∼30% when the substrate temperature is raised to 90 °C. The eye diagram of VCSEL operating at 2.125 Gb/s with 7 mA bias and 10 dB extinction ratio shows very clean eye with jitter less than 30 ps. We have accumulated life test data up to 5000 h at 100 °C/20 mA with exceptional reliability and the WHTOL (high temperature and high humidity 85 °C/85 operating lifetime) biased at 8 mA has passed over 2000 h.

Single mode 1.27-μm InGaAs:Sb-GaAs-GaAsP quantum-well vertical-cavity surface-emitting lasers

1.27 μm InGaAs:Sb-GaAs-GaAsP vertical cavity surface emitting lasers (VCSELs) were grown by metalorganic chemical vapor deposition (MOCVD) and exhibited excellent performance and temperature stability. The threshold current changes from 1.8 to 1.1 mA and the slope efficiency falls less than ~35% as the temperature raised from room temperature to 70oC. With a bias current of only 5mA, the 3dB modulation frequency response was measured to be 8.36 GHz, which is appropriate for 10 Gb/s operation. The maximal bandwidth is measured to be 10.7 GHz with modulation current efficiency factor (MCEF) of ~ 5.25 GHz/(mA)1/2. These VCSELs also demonstrate high-speed modulation up to 10 Gb/s from 25°C to 70°C.

Temperature-Dependent Photoluminescence of Highly Strained InGaAsN/GaAs Quantum Wells (λ= 1.28–1.45 µm) with GaAsP Strain-Compensated Layers

The effects of nitrogen incorporation into the In0.4Ga0.6As1-xNx/GaAs single quantum wells (SQWs), where x = 0.5 and 2%, grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD) were investigated using photoluminescence (PL) and high-resolution transmission electron microscopy (HRTEM). The evolution of the excitation-dependent PL and PL-peak position with temperature between 10 and 300 K shows that quantum-dot-like states occurred at that high nitrogen incorporation (x = 2%) and were confirmed by an HRTEM image which showed small dark regions about 2–3 nm in size was found in the interface of In0.4Ga0.6As0.98N0.02 and GaAs. Our investigations indicate that high nitrogen incorporation into the In0.4Ga0.6As1-xNx/GaAs system influenced carrier localization and might cause the formation of the dot-like states.