Data are presented demonstrating room-temperature operation of AlxGa1-xAs-GaAs vertical-cavity su... more Data are presented demonstrating room-temperature operation of AlxGa1-xAs-GaAs vertical-cavity surface-emitting lasers grown on Si substrates. The device structures are grown using molecular beam epitaxy and a grown-in quarter-wave AlAs-GaAs stack is used as the n-side reflector and a nonalloyed Ag dot used as the p-side reflector/contact. Pulsed threshold currents of ˜125 mA are obtained for a 15-μm-diam device.
Temperature-dependent Hall-effect measurements were carried out both in dark and in ambient light... more Temperature-dependent Hall-effect measurements were carried out both in dark and in ambient light on Si-doped AlxGa1-xAs layers grown by molecular-beam epitaxy over the entire composition range. Above 150 K, the measured Hall carrier densities (different from actual electron densities near the direct-indirect transition) show an exponential dependence on temperature. A shallow donor (<=15 meV) tied to the Γ band and a deep donor level tied to the L band were observed. The deep donor is dominant for x>0.2, and its activation energy Ed rises dramatically up to the direct-indirect band-gap crossover and peaks at 160 meV for x~0.48. As the A1 fraction increases further, Ed decreases, reaching 57 meV for AlAs. The error due to multivalley conduction on the measured values of Ed is shown to be negligible. The variation in Ed of the dominant donor level with x is accounted for by our theoretical calculations using a multivalley effective-mass model. A decrease of Ed with increasing doping densities is also observed. At high substrate-growth temperature, the incorporation of Si atoms was found to decrease. The persistent-photoconductivity (PPC) effect was observed with an increase in mobilities over the dark values in the entire composition range. The effect was most pronounced in the range 0.20<=x<=0.40. Traps related to the Si-doping density appear to be responsible for the observed photoconductivity effect. The ratio of the PCC traps and the Si atomic density is maximum at x~0.32 and is minimum in the direct-indirect band-gap crossover region.
Energy band profiles have been calculated for an np(+) InAlAs/InGaAs heterojunction employing var... more Energy band profiles have been calculated for an np(+) InAlAs/InGaAs heterojunction employing various grading widths. The minimum grading widths necessary for eliminating the conduction-band spike barrier are reported. The effect of bias is illustrated by plotting energy-band profiles for thermal equilibrium with a 0.5 V forward bias.
ABSTRACT Cascaded injection of Fabry-Perot lasers is proposed for improved performance in ASE see... more ABSTRACT Cascaded injection of Fabry-Perot lasers is proposed for improved performance in ASE seeded WDM PONs. Experimental results demonstrated better than 10dB improvement in power budget margin when ASE injection power is low.
Advanced Semiconductor Epitaxial Growth Processes and Lateral and Vertical Fabrication, Sep 1, 1992
We report on the fabrication and performance characteristics of (GaAs)3/(AlAs)1 short-period supe... more We report on the fabrication and performance characteristics of (GaAs)3/(AlAs)1 short-period superlattices (SPSs) quantum well lasers emitting at 737 nm. The SPSs consists of eight periods of 3 and 1 ML of GaAs and AlAs, respectively. The (GaAs)m/(AlAs)n SPSs have many advantages over their equivalent AlGaAs alloy counterparts. The broad area threshold current density, Jth, for 500 micrometers long lasers is 510 A cm-2. The 500 micrometers -long ridge waveguide lasers have a threshold current of 48 mA with a characteristic temperature of 68 K in the temperature range 19 to 60 degree(s)C. The external differential quantum efficiency near threshold is 0.58 mW/mA/facet. The devices lase in a single mode with spectral width within the resolution limit of the spectrometer.
Asia Communications and Photonics Conference 2013, 2013
ABSTRACT 10Gb/s upstream transmissions in C-band over 40km are demonstrated for symmetric TWDM PO... more ABSTRACT 10Gb/s upstream transmissions in C-band over 40km are demonstrated for symmetric TWDM PON system using tunable DBR lasers. Compared to NRZ, duobinary and PAM-4 signals with direct modulation result in significantly lower dispersion penalty (~1dB).
ABSTRACT Cascaded injection of Fabry-Perot lasers is proposed for improved performance in ASE see... more ABSTRACT Cascaded injection of Fabry-Perot lasers is proposed for improved performance in ASE seeded WDM PONs. Experimental results demonstrated better than 10dB improvement in power budget margin when ASE injection power is low.
Temperature-dependent Hall-effect measurements were carried out both in dark and in ambient light... more Temperature-dependent Hall-effect measurements were carried out both in dark and in ambient light on Si-doped Al x Ga 1-x As layers grown by molecular-beam epitaxy over the entire composition range. Above 150 K, the measured Hall carrier densities (different from actual electron ...
European Conference and Exhibition on Optical Communication, 2012
ABSTRACT This paper investigates wavelength plans for next generation hybrid TDM/WDM PONs. Simula... more ABSTRACT This paper investigates wavelength plans for next generation hybrid TDM/WDM PONs. Simulation results demonstrate that cost effective 10Gb/s directly modulated DFB laser at 1350nm is the best option for TDM/WDM PON downstream with 40km-reach and 1:64-split.
Data are presented demonstrating room-temperature operation of AlxGa1-xAs-GaAs vertical-cavity su... more Data are presented demonstrating room-temperature operation of AlxGa1-xAs-GaAs vertical-cavity surface-emitting lasers grown on Si substrates. The device structures are grown using molecular beam epitaxy and a grown-in quarter-wave AlAs-GaAs stack is used as the n-side reflector and a nonalloyed Ag dot used as the p-side reflector/contact. Pulsed threshold currents of ˜125 mA are obtained for a 15-μm-diam device.
Temperature-dependent Hall-effect measurements were carried out both in dark and in ambient light... more Temperature-dependent Hall-effect measurements were carried out both in dark and in ambient light on Si-doped AlxGa1-xAs layers grown by molecular-beam epitaxy over the entire composition range. Above 150 K, the measured Hall carrier densities (different from actual electron densities near the direct-indirect transition) show an exponential dependence on temperature. A shallow donor (<=15 meV) tied to the Γ band and a deep donor level tied to the L band were observed. The deep donor is dominant for x>0.2, and its activation energy Ed rises dramatically up to the direct-indirect band-gap crossover and peaks at 160 meV for x~0.48. As the A1 fraction increases further, Ed decreases, reaching 57 meV for AlAs. The error due to multivalley conduction on the measured values of Ed is shown to be negligible. The variation in Ed of the dominant donor level with x is accounted for by our theoretical calculations using a multivalley effective-mass model. A decrease of Ed with increasing doping densities is also observed. At high substrate-growth temperature, the incorporation of Si atoms was found to decrease. The persistent-photoconductivity (PPC) effect was observed with an increase in mobilities over the dark values in the entire composition range. The effect was most pronounced in the range 0.20<=x<=0.40. Traps related to the Si-doping density appear to be responsible for the observed photoconductivity effect. The ratio of the PCC traps and the Si atomic density is maximum at x~0.32 and is minimum in the direct-indirect band-gap crossover region.
Energy band profiles have been calculated for an np(+) InAlAs/InGaAs heterojunction employing var... more Energy band profiles have been calculated for an np(+) InAlAs/InGaAs heterojunction employing various grading widths. The minimum grading widths necessary for eliminating the conduction-band spike barrier are reported. The effect of bias is illustrated by plotting energy-band profiles for thermal equilibrium with a 0.5 V forward bias.
ABSTRACT Cascaded injection of Fabry-Perot lasers is proposed for improved performance in ASE see... more ABSTRACT Cascaded injection of Fabry-Perot lasers is proposed for improved performance in ASE seeded WDM PONs. Experimental results demonstrated better than 10dB improvement in power budget margin when ASE injection power is low.
Advanced Semiconductor Epitaxial Growth Processes and Lateral and Vertical Fabrication, Sep 1, 1992
We report on the fabrication and performance characteristics of (GaAs)3/(AlAs)1 short-period supe... more We report on the fabrication and performance characteristics of (GaAs)3/(AlAs)1 short-period superlattices (SPSs) quantum well lasers emitting at 737 nm. The SPSs consists of eight periods of 3 and 1 ML of GaAs and AlAs, respectively. The (GaAs)m/(AlAs)n SPSs have many advantages over their equivalent AlGaAs alloy counterparts. The broad area threshold current density, Jth, for 500 micrometers long lasers is 510 A cm-2. The 500 micrometers -long ridge waveguide lasers have a threshold current of 48 mA with a characteristic temperature of 68 K in the temperature range 19 to 60 degree(s)C. The external differential quantum efficiency near threshold is 0.58 mW/mA/facet. The devices lase in a single mode with spectral width within the resolution limit of the spectrometer.
Asia Communications and Photonics Conference 2013, 2013
ABSTRACT 10Gb/s upstream transmissions in C-band over 40km are demonstrated for symmetric TWDM PO... more ABSTRACT 10Gb/s upstream transmissions in C-band over 40km are demonstrated for symmetric TWDM PON system using tunable DBR lasers. Compared to NRZ, duobinary and PAM-4 signals with direct modulation result in significantly lower dispersion penalty (~1dB).
ABSTRACT Cascaded injection of Fabry-Perot lasers is proposed for improved performance in ASE see... more ABSTRACT Cascaded injection of Fabry-Perot lasers is proposed for improved performance in ASE seeded WDM PONs. Experimental results demonstrated better than 10dB improvement in power budget margin when ASE injection power is low.
Temperature-dependent Hall-effect measurements were carried out both in dark and in ambient light... more Temperature-dependent Hall-effect measurements were carried out both in dark and in ambient light on Si-doped Al x Ga 1-x As layers grown by molecular-beam epitaxy over the entire composition range. Above 150 K, the measured Hall carrier densities (different from actual electron ...
European Conference and Exhibition on Optical Communication, 2012
ABSTRACT This paper investigates wavelength plans for next generation hybrid TDM/WDM PONs. Simula... more ABSTRACT This paper investigates wavelength plans for next generation hybrid TDM/WDM PONs. Simulation results demonstrate that cost effective 10Gb/s directly modulated DFB laser at 1350nm is the best option for TDM/WDM PON downstream with 40km-reach and 1:64-split.
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Papers by Naresh Chand