A key to the utilization of nitride-arsenides for long wavelength optoelectronic devices is obtaining low defect materials with long nonradiative lifetimes. Currently, these materials must be annealed to obtain device quality material. The likely defect responsible for the low luminescence efficiency is associated with excess nitrogen. Photoluminescence and capacitance–voltage measurements indicate the presence of a trap associated with excess nitrogen which decreases in concentration upon anneal. Our films are grown by elemental source molecular beam epitaxy and the background impurity concentration is low, thus we have investigated the role of crystalline defects. High resolution x-ray diffraction showed improved crystal quality after anneal. We observed that the lattice parameter does not decrease linearly with nitrogen concentration for levels of nitrogen above 2.9 mol % GaN. The fact that Vegard’s law is not observed, despite theoretical calculations that it should, indicates that nitrogen incorporates in locations other than the group V lattice sites. X-ray photoelectron spectroscopy revealed that nitrogen exists in two bonding configurations in not-annealed material: a Ga–N bond and another nitrogen complex in which N is less strongly bonded to gallium atoms. Annealing removes this second nitrogen complex. A combined nuclear reaction analysis and channeling technique showed that not annealed GaNAs contains a significant concentration of interstitial nitrogen that disappears upon anneal. We believe that this interstitial nitrogen is responsible for the deviation from Vegard’s law and the low luminescence efficiency of not annealed GaNAs and GaInNAs quantum wells.

Group III–nitride–arsenides are promising materials for long wavelength opto-electronic devices grown on GaAs substrates. The growth of nitride–arsenides was performed in an elemental solid source molecular beam epitaxy system with a plasma cell to supply reactive nitrogen. Growth is carried out with plasma conditions that maximize the amount of atomic nitrogen versus molecular nitrogen, as determined from the emission spectrum of the plasma. The group III growth rate controls the nitrogen concentration in the film. The photoluminescence intensity of GaNAs and GaInNAs quantum wells (QWs) increases drastically and shifts to shorter wavelengths following high temperature anneal. Nitrogen diffusion out of the QWs is responsible for the wavelength shift. We observe a decrease of interstitial nitrogen after anneal. Vertical-cavity surface-emitting lasers with GaInNAs QWs demonstrated a continuous-wave operation. To limit nitrogen diffusion, the GaAs barriers surrounding the GaInNAs QWs were replaced by GaNAs barriers. This new active region resulted in devices emitting at 1.3μm.

A key to the utilization of nitride-arsenides for long wavelength optoelectronic devices is obtaining low defect materials with long nonradiative lifetimes. Currently, these materials must be annealed to obtain device quality material. The likely defect responsible for the low luminescence efficiency is associated with excess nitrogen. Photoluminescence and capacitance-voltage measurements indicate the presence of a trap associated with excess nitrogen which decreases in concentration upon anneal. Our films are grown by elemental source molecular beam epitaxy and the background impurity concentration is low, thus we have investigated the role of crystalline defects. High resolution x-ray diffraction showed improved crystal quality after anneal. We observed that the lattice parameter does not decrease linearly with nitrogen concentration for levels of nitrogen above 2.9 mol % GaN. The fact that Vegard's law is not observed, despite theoretical calculations that it should, indicates that nitrogen incorporates in locations other than the group V lattice sites. X-ray photoelectron spectroscopy revealed that nitrogen exists in two bonding configurations in not-annealed material: a Ga-N bond and another nitrogen complex in which N is less strongly bonded to gallium atoms. Annealing removes this second nitrogen complex. A combined nuclear reaction analysis and channeling technique showed that not annealed GaNAs contains a significant concentration of interstitial nitrogen that disappears upon anneal. We believe that this interstitial nitrogen is responsible for the deviation from Vegard's law and the low luminescence efficiency of not annealed GaNAs and GaInNAs quantum wells. (C) 2001 American Institute of Physics.

We describe low-threshold (/spl sim/1 mA) GaInNAs VCSELs emitting at a wavelength of 1.2 /spl mu/m under continuous-wave room temperature operation. The bottom mirror consists of a 22.5-period n-doped GaAs/AlAs distributed Bragg reflector (DBR) designed for a center wavelength /spl lambda/ near 1.2 /spl mu/m, the top mirror is a 20-period p-doped DBR with a Ti/Au contact electrode, and the GaAs /spl lambda/ cavity contains three 70 /spl Aring/ Ga/sub 0.3/In/sub 0.7/N/sub 0.02/As/sub 0.98/ quantum wells (QWs) separated by 200 /spl Aring/ GaAs barriers. The epilayers were grown by molecular beam epitaxy using solid source arsenic and a rf nitrogen plasma source. After growth, the top mirror was patterned by dry etching, and the three bottom-most AlAs layers were laterally oxidized, which formed square unoxidized apertures as small as 3.6 /spl mu/m on a side. Devices were mounted without heat sinking on a glass slide for optical emission through the substrate.

Group III-Nitride-Arsenides are promising materials for 1.3 micron opto-electronic devices grown on GaAs substrates, allowing AlAs/GaAs distributed Bragg reflector (DBR) mirrors and integration with GaAs electronics. Nitrogen decreases the GaAs bandgap dramatically, and the smaller GaN lattice constant results in less strain in GaInNAs compared to InGaAs. However, the anneal necessary to achieve device quality material shifts the emission peak to shorter wavelengths. Secondary ion mass spectroscopy (SIMS) depth profiling on GaInNAs quantum wells shows that nitrogen diffusion exceeds indium diffusion during anneal. We have demonstrated broad-area lasers, pulsed lasers, and CW VCSELs. However, due to nitrogen out-diffusion from the QWs, the operating wavelength of these initial devices was shorter than 1.23µm. Subsequent use of GaNAs barriers surrounding the QWs reduced the shift of the emission peak during anneal, as the GaAsN diffused nitrogen into the QW. This also resulted in longer wavelength emission due to decreased electron confinement energy and compensted overall strain. This new active region resulted in devices emitting at 1.3 micron. The new design also improved laser characteristic temperature T0 from 105K to 146K for similar devices.

Vertical cavity surface-emitting lasers (VCSELs) emitting near 0.85 /spl mu/m are becoming increasingly important for short-haul optical fiber transmission systems. These devices benefit from highly reflective and thermally conductive all-epitaxial GaAs-based mirrors and efficient transverse confinement through AlAs-oxide dielectric apertures. Extending this commercially-established technology to wavelengths in the 1.3-1.6 /spl mu/m range allows for dramatically increased transmission bandwidth and distance in conventional single- and multi-mode fiber. GaInNAs is a promising active layer material grown on GaAs that can achieve 1.3 /spl mu/m emission, and electrically pulsed broad-area GaInNAs VCSELs have been realized. We demonstrate for the first time low-threshold (/spl sim/1 mA) GaInNAs VCSELs emitting at a wavelength of 1.2 /spl mu/m under continuous-wave room temperature operation.

Summary form only given.GaAs-based vertical cavity surface emitting laser (VCSEL) diodes are becoming increasingly important in transmitters. By using GaInNAs MQW active regions, the emission wavelength of GaAs-based lasers can be extended into the range of 1200-1300 nm. In addition, the reduced temperature sensitivity of this active region allows for the possibility of uncooled transmitter operation.

Elemental source molecular beam epitaxy was used to grow InGaNAs quantum well samples, edge-emitting laser diodes, and vertical-cavity laser diodes on GaAs substrates. The quantum well samples exhibited an as-grown room temperature photoluminescence peak beyond 1310 nm which both increased dramatically in intensity and blueshifted with thermal annealing. Edge emitting laser diodes had threshold current densities as low as 450 and 750 A/cm2 for single and triple quantum well active regions, respectively, and emitted light at 1220–1250 nm. The vertical cavity laser diodes emitted light at 1200 nm and had threshold current densities of 3 kA/cm2 and efficiencies of 0.066 W/A.

Elemental source molecular beam epitaxy has been used to grow vertical cavity laser diodes on GaAs substrates that employ GaInNAs multiquantum well active regions and AlAs/GaAs distributed Bragg reflectors. The laser diodes emitted light at 1200 nm and had threshold current densities of 2.5 kA/cm2 and efficiencies of 0.066 W/A under room temperature pulsed operation.

Vertical cavity surface-emitting lasers (VCSELs) are becoming increasingly important for short-haul optical fiber transmission systems. Given the commercial success of GaAs-based 850 nm VCSELs, dramatic enhancements in transmission bandwidth and distance can be achieved in conventional single- and multi-mode fiber by extending the emission wavelength to the 1300 nm-1550 nm range. GaInNAs is a promising active layer material grown on GaAs that can achieve 1300 nm emission (Kondow et al., 1997), and electrically pulsed broad-area GaInNAs VCSELs (Larson et al., 1998; Coldren et al., 2000) have been realized. Here, we take advantage of the properties of GaAs-based materials-thermally-conductive high contrast mirrors and AlAs-oxide current apertures-to demonstrate for the first time low-threshold (/spl sim/1 mA) GaInNAs VCSELs emitting at a wavelength of 1200 nm under continuous-wave (CW) room temperature operation.

Nitride-Arsenides are promising materials for long wavelength opto-electronic devices grown on GaAs substrates. The photoluminescence intensity of GaNAs and GaInNAs quantum wells increases drastically and shifts to shorter wavelengths following high temperature anneal. Study of PL after different annealing conditions revealed that the wavelength shift and the intensity increase occur together. We observe a decrease of interstitial nitrogen after anneal, probably resulting in the increased luminescence efficiency. Nitrogen diffusion out of the QWs is responsible for the wavelength shift. To limit nitrogen diffusion, the GaAs barriers surrounding the GaInNAs QWs were replaced by GaNAs barriers. This new active region resulted in devices emitting at 1.3 mum.

We report, for the first time, room temperature continuous-wave (CW) operation of GaInNAs vertical-cavity surface-emitting laser diodes emitting at a wavelength of 1.2 mum and grown all-epitaxially in a single step on a GaAs substrate, Oxide-apertured devices demonstrated CW threshold currents as low as 1 mA, slope efficiency above 0.045 W/A, and thermal impedance of 1.24 K/mW. Larger sized devices exhibited pulsed threshold current density of 2-2.5 kA/cm(2) and slope efficiency above 0.09 W/A.

Employing InGaNAs materials, low wavelength active regions with emission at 1.3 /spl mu/m have been developed on GaAs substrates. Broad area, single quantum well, in-plane lasers with thresholds as low as 1.1 kA/cm/sup 2/ were fabricated.

We employ a combination of direct fiber coupling and broad-band add/drop filtering to demonstrate a 4-wavelength by 10-fiber VCSEL-based transmitter in a PGA package with MT-connectorized optical output. This is the first demonstration to our knowledge of a multiwavelength VCSEL-based parallel optical fiber transmitter. Such a device is useful for future high-bandwidth low-cost data communications applications. The use of a hybrid packaging scheme employing a fiber-ribbon-guided add/drop filter enables ten fibers by four wavelengths with a wide (>10 nm) channel spacing; more wavelengths should be achievable either by using additional filters and/or by combining this approach with monolithic techniques of achieving multiple wavelengths per VCSEL die

We demonstrate a grating-router with 37 nm channel spacing and 6 nm FWHM in the 800-900 nm range for WDM over multimode fiber. Broadband thin-film add/drop filters provide wavelength re-use enabling N/spl times/N fully non-blocking interconnection with N wavelengths.

Micromachined wavelength tunable vertical cavity lasers are attractive for applications ranging from wavelength division multiplexing to spectroscopy. An improved tunable structure that incorporates a partial anti-reflection coating to increase coupling between the air gap and the semiconductor cavity, and a more flexible micromachine process that enables independent optimization of the central reflector region and deformable membrane structure are described. This combination of structural and process modifications enables decoupling the tradeoffs between wavelength tuning rate and threshold current, as well as the tradeoffs between top mirror reflectance and tuning voltage. With these improved approaches, a 2.5 pair dielectric distributed Bragg reflector hybrid membrane top mirror produced singlemode devices with a 23 nm wavelength tuning range and multi-transverse-mode devices with a 30 nm wavelength tuning range. Threshold current, differential quantum efficiency, and lasing mode are characterized as a function of membrane bias.

Wavelength tunable lasers are attractive for Wavelength Division Multiplexing (WDM) applications. Conventional WDM relies on fixed wavelength laser arrays, which have temperature-control, system reliability, and manufacturability problems. Because of these shortcomings, wavelength tunable lasers are indispensable elements of such an array since the lasing wavelength of each laser can be set, maintained, or changed to any wavelength within its tuning range. Tunable vertical cavity lasers are optimum for such an array because their short cavity length translates into a single longitudinal mode inside the laser's gain spectrum. This allows continuous tuning without mode hopping. Our approach to tunable VCSEL uses a micromachined suspended deformable membrane that also functions as the top mirror above the semiconductor cavity. Modulating the air gap thickness by applying a bias between the membrane and the semiconductor cavity results in an additional phase shift that effectively modulates the resonance frequency of the VCSEL.

Wavelength tunable VCSELs are potentially useful for wavelength division multiplexing. Following our previous success in wavelength tunable VCSELs, we recently achieved 25 nm continuous wavelength tuning using a newly developed process that enables the use of more mirror pairs without sacrificing tuning voltage, We have also observed whispering gallery modes in round central reflector devices.