H. C. Yu

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.

Characteristics of MOCVD- and MBE-grown InGa(N)As VCSELs

We report our results on InGaNAs/GaAs vertical-cavity surface-emitting lasers (VCSELs) in the 1.3 ?m range. The epitaxial structures were grown on (1?0?0) GaAs substrates by metalorganic chemical vapour deposition (MOCVD) or molecular beam epitaxy (MBE). The nitrogen composition of the InGa(N)As/GaAs quantum-well (QW) active region is 0?0.02. The long-wavelength (up to 1.3 ?m) room-temperature continuous-wave (RT CW) lasing operation was achieved for MBE- and MOCVD-grown VCSELs. For MOCVD-grown devices with n- and p-doped distributed Bragg reflectors (DBRs), a maximum optical output power of 0.74 mW was measured for In0.36Ga0.64N0.006As0.994/GaAs VCSELs. A very low Jth of 2.55 kA cm?2 was obtained for the InGaNAs/GaAs VCSELs. The MBE-grown devices were made with an intracavity structure. Top-emitting multi-mode 1.3 ?m In0.35Ga0.65N0.02As0.98/GaAs VCSELs with 1 mW output power have been achieved under RT CW operation. A Jth of 1.52 kA cm?2 has been obtained for the MBE-grown In0.35Ga0.65N0.02As0.98/GaAs VCSELs, which is the lowest threshold current density reported. The emission characteristics of the InGaNAs/GaAs VCSELs were measured and analysed.

Highly Strained 1.22-

In this work, the highly strained In0.39Ga0.61As-GaAs lasers grown by metal-organic vapor phase epitaxy were studied. The InGaAs lasers could emit at 1.22 mum under continuous-wave conditions, whereas the threshold current density (Jth) and transparency current density (Jtr) were 140 and 37.2 A/cm2, respectively. To the best of our knowledge, the Jtr was the lowest among the reported InGaAs lasers longer than 1.2 mum. The characteristic temperature (To) was 146.2 K indicating the good temperature stability. These excellent laser characteristics could be attributed to the optimized growth conditions.

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The conduction and interface states of laterally wet-oxidized GaAs-AlGaAs-GaAs structures after various oxidation times are investigated. Effective current blocking is achieved after 150min oxidation and the conduction of current through the oxidized AlGaAs layer is controlled by the Poole-Frenkel mechanism, from which a relative dielectric constant of 7.07 is obtained. At an oxidation time of 15min, capacitance-voltage spectra exhibit capacitance dispersion over frequency, implying the presence of an interface state. The intensity of the dispersion increases with increasing the oxidation time and admittance spectroscopy reveals a significant interface state at ∼0.28eV at 45min. Further increasing the oxidation time to 150min broadens the interface state to a set of continuous interface states from 0.19–0.31eV with decreasing densities from 3×1011to0.9×1011eV−1cm−2 and generates fixed charges of about 9.1×1011cm−2 in the oxidized layer. By comparison to a similar trap in a relaxed InGaAs∕GaAs, the interfa...

m InGaAs Lasers Grown by MOVPE

Molecular-beam-epitaxy growth of high structural and optical-quality InGaAsN∕GaAs quantum wells (QW) has been investigated. The material quality can be improved significantly by using low-temperature growth to suppress the phase separation. High-performance ridge-waveguide InGaAsN∕GaAs single QW lasers emitting at 1.3μm have been demonstrated. Infinite-cavity-length threshold-current density of 400A∕cm2, internal quantum efficiency of 96%, and a slope efficiency of 0.67W∕A for a cavity length L=1mm were obtained. A TO46 packaging laser shows single lateral-mode kink-free output power of more than 200mW with a maximum total wallplug efficiency of 29% at room temperature under continuous wave (cw) operation. Moreover, 1.3μm InGaAsN∕GaAs QW vertical-cavity surface-emitting lasers with a threshold current density lower than 2KA∕cm2 at room temperature have been achieved. We obtained multimode cw output power and slope efficiency in excess of 1mW and 0.15W∕A, respectively.

Evolution of conduction and interface states of laterally wet-oxidized AlGaAs with oxidation time

In this letter, the strained In_0.22Ga_0.78As-GaAs single quantum-well lasers grown by metal-organic vapor phase epitaxy were studied. The lasing wavelength of the fabricated InGaAs laser was 1056 nm, whereas the internal loss (alpha_i) and the transparency current density (J_tr) were 1.78 cm^-1 and 40.2 A/cm², respectively. By using the GaAsP-GaAs superlattices as strain-compensated layer, the lasing wavelength was 1052 nm, and the alpha_i and J_tr could be reduced to 0.63 cm^-1 and 39.1 A/cm², respectively. To the best of our knowledge, the J_tr was the lowest among the reported InGaAs lasers around 1060 nm.

Molecular-beam-epitaxy growth of high-quality InGaAsN∕GaAs quantum well lasers emitting at 1.3μm

High-temperature stability of lasing wavelength of GaAsSb/GaAs quantum well (QW) lasers grown by metal-organic vapor phase epitaxy will be demonstrated. According to the best of our knowledge, this is the first trial of using triethylgallium (TEGa) as the precursor to grow QW at low temperature (525°C). The lasing wavelength ranges from 1117 to 1144 nm and varies with temperature (dλ/dT) from 0.24 to 0.287 nm/K. These values are lower than other previously reported results. The QW grown at high temperature (600 °C) by using trimethylgallium (TMGa) is also examined. The lasing wavelength is 1125.6 nm at room temperature and dλ/dT is 0.36 nm/K, which is higher than those lasers grown at lower temperature.

Low Transparency Current Density and Low Internal Loss of 1060-nm InGaAs Laser With GaAsP–GaAs Superlattices as Strain-Compensated Layer

In this letter, we report the high-temperature stability of a lasing wavelength in GaAsSb/GaAs quantum-well (QW) lasers grown by metal-organic vapor phase epitaxy. To the best of our knowledge, this is the first successful use of triethylgallium (TEGa) as the precursor to grow GaAsSb/GaAs QW at low temperature (525degC). The lasing wavelength ranges from 1117 to 1144 nm and varies with temperature (dlambda/dT) from 0.24 to 0.287 nm/K. These values are lower than those of other results reported previously. The QW grown at high temperature (600degC) using trimethylgallium (TMGa) is also examined. The lasing wavelength is 1125.6 nm at room temperature, and dlambda/dT is 0.36 nm/K; the latter value is higher than those grown at lower temperature.

High-temperature stability of lasing wavelength in GaAsSb/GaAs double quantum wells lasers

We have demonstrated the fabrication and characterization of single-layered hybrid polymer-quantum dot light-emitting diodes (PQD-LEDs) with the emissive composite film of 2,3-dibutoxy-l,4-poly(phenylene vinylene) (DBPPV) and CdSe/ZnS core/shell quantum dots (QDs). The electrical and optical characteristics are significantly influenced by the thickness of the emissive layer. When the thickness of composite film is thinned to about 103 nm, the maximum luminance of 4100 cd/m2 as well as maximum luminous efficiency of 1.35 cd/A can be achieved at 9.6 V and 7.6 V, respectively. However, the electroluminescence spectra reveal that the emission contribution is dominated by the emission from DBPPV. A maximum ratio of emission intensity of QDs to that of DBPPV is about 38 %, which indicates the contribution of QDs is minor. In addition, the post- annealing effect on device performance was also investigated. In contrast to previous reports, no obvious improvement can be observed by post-annealing.

High-Temperature Stability of Lasing Wavelength in GaAsSb/GaAs QW Lasers

Metal–semiconductor–metal photodetectors (MSM-PDs) with transparent ITO contacts were studied. The RF-sputtered ITO layers were formed under various ambient gases Ar, Ar/N2, and Ar/O2. The ITO film fabricated under the Ar/O2 ambient has highest Schottky barrier-height, but the high resistivity limited the photocurrent of the photodetectors. Consequently, using Ar/N2 as the plasma gas would be a suitable choice for MSM-PD application. The photo/dark current ratios of the MSM-PDs were 5, 25 and 12 (measured under 0.2 V) using Ar, Ar/N2 and Ar/O2 as the plasma gases. To further improve the photo/dark current ratio, we fabricated the InGaAN-PDs using metal–insulator–metal–semiconductor (MIMS) structures. The dark current was greatly suppressed by the SiO2 layer, and the highest photo/dark current ratio was 66 under 0.2 V bias.