Chih-Wei Hu

High-Reliable and High-Speed 1.3

In this paper, we report the fabrication of high-reliability and high-speed 1.3 mum complex-coupled distributed feedback (CC-DFB) buried heterostructure (BH) laser diodes (LDs) with Fe-doped InGaAsP/InP hybrid grating layers. High optical coupling coefficient and eminent current confining ability are accomplished by combining the Fe-doped InGaAsP/InP current-blocking-grating (CBG) layers to provide both the distributed-feedback index-and gain-coupling coefficients. Besides, the narrow-stripe BH LDs are implemented by burying the active region with a Fe-doped InP current-blocking layer during the epitaxial regrowth. The fabricated CBG CC-DFB BH LDs at 20degC shows a low threshold current of 5.3 mA, a maximum light output power of 36 mW at 100 mA, a high slope efficiency of 0.41 mW/mA, and a side-mode suppression ratio (SMSR) of 42 dB at twice the threshold. In addition, these LDs exhibit a maximum operation temperature of 125degC, an extremely low threshold current of 15.8 mA at 90degC, a small variation in slope efficient of only -1 dB in the temperature range from 20degC to 80degC, and a characteristic temperature of 77 K and 56 K between 20 degC and 60degC, and 70degC and 120degC, respectively. Furthermore, these 1.3 mum CBG CC-DFB BH LDs exhibit a high-speed characteristic up to 11.8 GHz at room temperature and an estimated median lifetime of more than 1.1 times 105 h or 12.5 years at 5 mW and 85degC.

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In this article, we investigate the formation and optical properties of 3-monolayer (ML) InAs quantum dots (QDs) on the InGaAs strain buffer layer (SBL) grown by metallorganic chemical vapor deposition (MOCVD). As compared to the InAs QDs directly grown on a GaAs surface, the InAs QDs grown on an InGaAs SBL can increase the dot density from 1.7 to 3.5 X 10 10 cm -2 and improve the uniformity. Using microphotoluminescence (μ-PL) measurements, the power-dependent PL at low temperatures shows the ground, first, and second states of InAs QDs due to the state-filling effect at the highest excitation power density of 11900 W/cm 2 . The temperature-dependent PL spectra shows that the PL peak energy has a redshift following the Varshni relation and an unusual temperature dependence of the linewidth, which first reduces and then increases with temperature for the InAs QDs grown on the InGaAs SBL. The PL thermal quenching is determined by the carrier escape from the QDs to the nonradiative recombination centers. The peak wavelength and full width at half maximum of PL spectra at 280 K for the InAs QDs grown on an InGaAs SBL are 1306 nm and 21.5 meV, respectively.

m Complex-Coupled Distributed Feedback Buried-Heterostructure Laser Diodes With Fe-Doped InGaAsP/InP Hybrid Grating Layers Grown by MOCVD

The fabrication and characteristics of 1.3-/spl mu/m InGaAsP strain-compensated multiquantum well (SCMQW) buried heterostructure (BH) laser diodes (LDs) grown by selective metal-organic chemical vapor epitaxy on a patterned InP substrate are demonstrated. The photoluminescence (PL) of the SCMQW active region grown on the patterned grooves has a narrow full-width at half-maximum of /spl sim/ 47 meV. The BH LDs exhibit a threshold current of 6.8 mA, a slope efficiency of 0.45 mW/mA, and a light output power exceeding 30 mW at 80 mA and 20/spl deg/C. The maximum operating temperature is 120/spl deg/C with a characteristic temperature of 72 K in 20/spl deg/C-80/spl deg/C. The 3-dB modulation bandwidth can be extended as far as 11.4 GHz under a bias level of 40 mA, and the back-to-back tests show a clear and symmetric eye diagram at 10 Gb/s with a PRBS of 2/sup 31/-1 word length and a peak-to-peak voltage of 1.08 V at 85/spl deg/C. The average increase in operational current is smaller than 0.84% after the 1500-h aging test. The mean time of the BH LDs operated at 85/spl deg/C to fail is calculated as 9/spl times/10/sup 4/ h. These BH LDs satisfy the reliability requirement for strict loop environment and 10-Gb Ethernet application without special hermetic packaging.

Temperature Dependent Photoluminescence of Self-Organized InAs Quantum Dots on an InGaAs Strain Buffer Layer Grown by MOCVD

In this letter, we utilize a self-terminated oxide polish (STOP) planarization technique to fabricate high-yield, high-performance, low-cost, and uncooled 1.3-mum ridge-waveguide AlGaInAs-InP laser diodes (LDs). The STOP technique is superior to the polyimide planarization, which suffers from high-temperature sustainability. The LDs fabricated by the STOP technique exhibit threshold currents of 8.5 and 30.5 mA, and light output powers of 25.9 and 4.8 mW at 100 mA for 20degC and 110degC, respectively. The characteristic temperatures (T 0) are 82.6 K from -30degC to 80degC and 55.9 K from 80degC to 110degC. Since the metal pad lies on a thick SiO2 layer, the parasitic capacitance can be effectively lowered to 2 pF. The 3-dB modulation bandwidths of the LDs at 50 mA are 12.1 and 9.44 GHz at 20degC and 90degC, respectively

High-speed and uncooled operation of 1.3-/spl mu/m InGaAsP strain-compensated MQW BH lasers fabricated on patterned InP substrates

In this letter, we proposed an alternate method by using the Fe-doped InGaAsP-InP hybrid grating layers to fabricate the 1.3-/spl mu/m current-blocking-grating complex-coupled distributed-feedback (CBG CC-DFB) laser diodes (LDs) grown by metal-organic chemical vapor deposition (MOCVD). By combining the Fe-doped InGaAsP-InP grating layers, the CBG CC-DFB LDs can provide high optical DFB coupling coefficient and high current confining ability. Moreover, the current aperture in the lateral direction can be easily controlled by the self-aligned MOCVD regrowth process. Therefore, the manufacture of CBG CC-DFB buried heterostructure LDs is easy as the ridge-waveguide LDs. The LDs exhibit a low threshold current of 5.3 mA, a high slope efficiency of 0.42 mW/mA, and a stable single mode with a high sidemode suppression ratio of /spl sim/42 dB at two times the threshold (10.5 mA). Even at high temperatures, these LDs still have an extremely low threshold current of 15.8 mA at 90/spl deg/ and a small variation in slope efficient of only -1 dB at the temperatures between 20/spl deg/ and 80/spl deg/. Furthermore, these LDs show a high-speed characteristic of more than 11.8 GHz at 20/spl deg/, which are suitable for 10-Gb/s Ethernet and OC-192 applications.

Low-cost and high-performance 1.3-/spl mu/m AlGaInAs-InP uncooled laser diodes

In this article, we report on an alternative method to fabricate high-efficiency planar-type oxide-confined 1.3-/spl mu/m vertical-cavity surface-emitting lasers (VCSELs). The planarized process of VCSELs uses silicon oxide (SiO/sub x/) as a buried layer. The devices exhibit excellent static characteristics at room temperature, including a threshold voltage of 2 V corresponding to a threshold current of 3.5 mA, and a maximum light output power of 1.86 mW measured at 15 mA. To our knowledge, this output power is the best when compared to those obtained with conventional VCSEL processes for the similar epitaxial structure design (reference of the OLD values). The VCSELs show a threshold current density of 3100 A/cm/sup 2/, a differential resistance at half of the maximum power of 110 /spl Omega/, a slope efficiency of 0.22 W/A above the threshold, and a continuous wave operation temperature of up to 80/spl deg/C. In addition, when operating at 4 mA these devices exhibit a single-mode emission with the transverse-mode suppression of more than 20 dB and an output power of 0.12 mW. The wavelength of the strongest emission peak, which corresponds to the fundamental transverse mode, increases with injection current at a red shift of 0.45 nm/mA from 1280.6 nm at 4 mA to 1284.4 nm at 12 mA due to a joule effect. Finally, this planar-type 1.3-/spl mu/m VCSEL shows a clear and symmetric eye diagram operating at 2.488 Gb/s at 12 mA. These results confirm the SiO/sub x/-planarized GaInNAs VCSELs have the potential capacity for fiber optic applications.

Uncooled 1.3-/spl mu/m complex-coupled DFB BH laser diodes with the Fe-doped InGaAsP-InP hybrid current-blocking grating

We report on the optimization of Ga0.27In0.73As0.67P0.33/Ga0.11In0.89As0.24P0.76 compressive-strain multiple-quantum-well (CS-MQW) grown by low-pressure metalorganic chemical vapor deposition for 1.3-µm ridge-waveguide laser diodes (LDs). The structural and optical properties are characterized by doublecrystal x-ray diffraction and photoluminescence (PL) measurements, respectively. The optimum thicknesses of the well, barrier, and waveguide layer of the active region are 4 nm, 10 nm, and 100 nm, respectively. The GaInAsP/GaInAsP CS-MQW as-cleaved LDs with the optimum active region, a 3.5-µm-width ridge, and a 900-µm-cavity length exhibit the threshold current density of 1.09 kA/cm2, a differential quantum efficiency of 30%, a characteristic temperature of 60 K, a maximum operating temperature up to 75°C, and a redshift rate of 0.30 nm/°C.

High-performance SiO/sub x/ planarized GaInNAs VCSELs

In this article, we demonstrate a simple and low-cost method to fabricate the 1.55 μm strained multiquantum-well InGaAsP/InP buried-heterostructure (BH) laser diodes (LDs) by using the single-step metallorganic-chemical-vapor-deposition (MOCVD) regrowth and self-aligned technique. The active region is buried by the intrinsic InP layer which is used as the current-blocking layer as well as the electrical and optical confinement layer. The BH LDs have a calculated internal quantum efficiency of 81% and an internal loss of 21.5 cm -1 . The fabricated as-cleaved BH LDs exhibit a threshold current of 6.5 mA, a maximum light output power of 21 mW at 100 mA, a maximum operating temperature of 100°C, and a characteristic temperature of 72 K in 20-60°C. The BH LDs with an as-cleaved front facet and a high reflectivity coating (∼92%) applied to the rear facet can increase the maximum operation temperature up to 125°C and have a light output power exceeding 10 mW at 80 mA and 100°C. The 3 dB frequency at a bias current of 40 mA is 8.0, 6.5, and 5.2 GHz at 30, 60, and 90°C, respectively. Besides, the 3 dB modulation bandwidth can be extended as far as 10.5 GHz at 20°C and 60 mA. These results confirm that BH LDs have the potential capacity for high-speed fiber optic applications.

Optimization of active region for 1.3-µm GalnAsP compressive-strain multiple-quantum-well ridge waveguide laser diodes

In this letter, we investigate and characterize the 1.3-mum single-mode vertical-cavity surface-emitting lasers (VCSELs) with two GaInAsN strained multiple quantum wells as the active region. Surface relief technique and a thick silicon oxide were used for the spatial mode filtering and the planarization processing, respectively. The VCSELs with a 5-mum-diameter surface-relief aperture and a 12-mum-diameter oxide-confined aperture at room temperature exhibit a threshold current of 3 mA, a slope efficiency of 0.14 mW/mA, a maximum operation temperature of 90 degC, and a single-mode behavior. These VCSELs show a maximum light output power of 1 mW for the single fundamental mode with a transverse-mode suppression of more than 30 dB and also show a clear eye-opening feature operated at 2.488 Gb/s and 12.6 mA

High Performance 1.55 μm InGaAsP Buried-Heterostructure Laser Diodes Fabricated by Single-Step MOCVD Regrowth and Self-Aligned Technique

In this article, an alternative method is presented to fabricate a planar-type oxide-confined 850-nm vertical-cavity surface-emitting laser (VCSEL). The threshold voltage, threshold current, light output power, external differential quantum efficiency, emission spectrum, and dynamic response of VCSELs planarized with a silicon oxide (SiOx) have been evaluated. These devices exhibit excellent static characteristics, including a threshold voltage (Vth) of 2.05V corresponding to a threshold current of 0.88mA, a minimum threshold current of 0.7mA near 60°C, a maximum output power of 4.28mW at 11mA, a maximum external differential quantum efficiency (ηex) of 43% just above threshold, and an operation temperature beyond 130°C. In addition, the transverse modes of the device initially are low-order, while high-order modes appear at elevated current levels. The fundamental transverse mode at the longest wavelength increases with injected current with a redshift of 0.49nm∕mA due to the Joule effect. Since the ther...