The dark current of a photodetector is a key parameter for high-sensitivity optical receivers. We report low-dark-current, triple-mesa avalanche photodiodes that have ~50 times lower dark current than conventional single-mesa devices, and suppress surface leakage. The tolerances of triple-mesa avalanche photodiode parameters are presented.

Mid-infrared (mid-IR, lambda approximate to 3-12 mu m) photonic integrated circuits on low-loss passive waveguide platforms are of significant interest for a wide range of mid-IR applications. Quantum cascade lasers (QCLs) are currently the only room-temperature electrically pumped semiconductor light sources that can operate in a continuous-wave at room temperature over the entire mid-IR spectral range. Given very high thermal dissipation in QCL active regions, achieving long-term reliability and continuous-wave operation of heterogeneously integrated devices on silicon platforms is challenging. Here we experimentally demonstrate homogeneous integration of mid-IR QCLs with low-loss In0.53Ga0.47As passive waveguides epitaxially grown on InP substrates. The homogeneous integration approach uses materials, growth, and processing steps nearly identical to those used for conventional high-performance mid-IR QCLs, which offers superior reliability and performance of photonic integrated circuits. Over 0.57 W of peak-pulsed optical power was coupled to the passive waveguide from a homogeneously integrated n lambda approximate to 4.6 mu m QCL, which represents an order of magnitude improvement in optical power compared to the best results obtained with heterogeneously integrated QCLs. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

We experimentally demonstrate lasing and mode coupling of mid-infrared quantum cascade lasers monolithically integrated with passive InGaAs waveguides for integrated-photonics applications. A waveguide-coupled device produced 30 mW peak power with J th =3.5 kA/cm 2 at room-temperature.

A method of wafer bonding is demonstrated which significantly reduces the thermal expansion mismatch stress, by removing the substrate before the high temperature anneal, thereby allowing elastic accommodation of the thin device layers. Record low dark current Si/InGaAs pin detectors have been realized

As the p-type dopant most often used in metalorganic chemical vapor deposition (MOCVD) of Group III - Group V compound semiconductors, Zn presents problems in device design and performance because of its high diffusivity in these materials. While Zn diffusion into n-type layers such as InP:S has been observed frequently, there is little known as to the electronic and optical properties of the resultant material. We have grown InP samples by MOCVD which are doped with both Zn and S to levels as high as 3×1018 cm-3. These samples were analyzed by electrochemical C-V profiling, van der Pauw-Hall analysis, secondary ion mass spectroscopy (SIMS), and low temperature (10K) photoluminescence spectroscopy (PL). We have determined that good hole mobility is maintained in InP:Zn samples that are simultaneously doped with S up to a level of 4×1017 cm-3. PL analysis of co-doped samples shows peaks between 0.91 and 0.92 µm which are indicative of donor-acceptor transitions, and broad peaks with energy levels of approximately 1.0 µm which may be indicative of ZnS complexes or precipitates. SIMS analysis of Zn diffusion into Fe doped substrates shows that Zn diffusion is reduced in the presence of S in the lattice.

The diffusion characteristics and incorporation characteristics of Zn dopants in OMVPE-grown InP are studied. The Zn diffusion constant depends strongly on concentration and increases by four orders of magnitude in the Zn concentration range 2×1018–8×1018 cm−3. This drastic concentration dependence of the Zn diffusion constant is shown to determine the Zn incorporation characteristics during OMVPE growth. A spread of Zn dopants into intentionally undoped regions may result at high Zn doping concentrations in InP.

Zn-doped InP and GaInPAs layers were grown by OrganoMetallic Vapor-Phase Epitaxy (OMVPE). The epitaxial films consist of a primary GaInPAs/InP epitaxial layer and a secondary InP/GaInAs epitaxial layer. We present evidence that the redistribution of Zn acceptors in the primary epitaxial layer is strongly influenced by the Zn doping concentration in the secondary epitaxial layer. Rapid redistribution of Zn acceptors in the primary epitaxial layer occurs if the Zn doping concentration in the secondary epitaxial layer exceeds a critical concentration ofNZn≅3×1018cm−3. The influence of the growth temperature on this effect is also presented.

The use of Tetraethyltin (TESn) as a source of donors in GaAs and its A1xGal-xAs alloys with x varied from 0 to 1 has been investigated for the growth of heterostructures by low pressure metalorganic chemical vapor deposition. (LP-MOCVD). The donor activity increases in the binary and ternary alloys as a function of tetraethyltin molar flow fraction and with increasing temperature. High quality one quarter wave Distributed Bragg reflectors (DBRs) were grown with TESn as an n type dopant source with no degradation in reflectivity observed. No surface accumulation of tin was observed and the morphology of all epitaxial samples was excellent. Sn incorporation in AlAs produced n type material as determined by Van der Pauw Hall measurements. The use of TESn as a convenient and controllable dopant source in structures such as vertical cavity surface emitting lasers which incorporate DBRs as well as other heterostructure devices is therefore practical..

Five-micron long AlGaAs/GaAs Fabry–Pérot vertical cavities with thin GaAs active regions of two different thicknesses are analyzed both theoretically and experimentally in terms of their optical transmission characteristics, spontaneous radiation patterns, and spontaneous spectral emission characteristics. The effects on spontaneous emission of the precise placement of the GaAs active region and also the thickness of this region, as compared to the emitted wavelength, are demonstrated. The measured results are compared with theoretical calculations which are based on the first-order perturbation field theory presented in an earlier publication. Good agreement is found in the comparison between the theoretical predictions and the experimental results, and indicates the controllable spontaneous emission in these long vertical cavities.

Heterostructures of InGaAs/InP and InGaAs/InGaAsP were grown by low pressure metalorganic chemical vapor deposition (LP-MOCVD) in an EMCORE GS3200 system. Highly abrupt interfaces were attained with PL line widths for the InGaAs/InP system comparable to the best values reported in the literature for any crystal growth technique, MOCVD, MBE or CBE. These structures were characterized with low temperature (10K) photoluminescence (PL), transmission electron microscopy (TEM) and high resolution X-ray diffraction (HRXD).

There is currently a great deal of interest in the use of small optical cavities to control the spontaneous emission characteristics from semiconductor light emitting diodes and lasers. Predictions of the magnitude to which the effect may be realized range from novel forms of lasers having "zero-threshold", to skepticism as to whether controlled spontaneous emission may impact practical devices at all since it simply represents "filtering". Therefore, experimental investigations which elucidate the role controlled spontaneous emission may play in present day realizable device structures are needed.

It has recently been demonstrated that somewhat anomalous spectral characteristics are achieved in the emission from localized dipoles contained in Fabry–Perot cavities. More extensive data are presented demonstrating the spectral characteristics of emission from 5-μm-long AlGaAs Fabry–Perot cavities containing spatially localized dipoles. The dipole localization is achieved by using a GaAs quantum well, and the quantum well is placed a quarter emission wavelength away from one of the cavity reflectors. The spectral characteristics are derived analytically using a model that accounts for interference between two simultaneously emitted coherent spontaneous wave packets which travel in opposite directions upon emission.

Data are presented demonstrating the influence of the precise placement of a GaAs quantum well in a 5 μm long AlGaAs vertical cavity. It is shown that, even for this relatively long cavity, when the emitting dipoles are confined to a region significantly less than the optical wavelength, the quantum well placement influences not only the spectral shape of the emitted light but also the spectrally integrated intensity. Cavity structures are characterized using transmission measurements, spectral emission, and radiation patterns.

Data is presented on the characteristics of light emitted from localized dipoles contained in Fabry–Perot cavities. The cavities consist of AlGaAs semiconductor with the dipole localization achieved using GaAs quantum wells. Experimental data shows that the standard assumption of the spectral width of a cavity mode as having some fixed relationship to the photon lifetime in the cavity is an approximation which only becomes valid for dipoles throughout the cavity. Also, intensity differences are measured out either side of a cavity even when symmetrical mirrors are used. The intensity difference depends on the precise dipole position. Both the spectral and intensity differences can be derived from theory using a model which accounts for interference between coherent spontaneous wavepackets emitted in opposite directions from individual emission events.

Data are presented demonstrating controlled spontaneous emission in room-temperature AlGaAs-GaAs Fabry–Perot microcavities, which utilize high contrast Bragg reflectors. The reflector materials are a CaF2/ZnSe combination. A GaAs quantum well contained in the microcavities is excited using a low power He-Ne laser, and the spontaneous emission characteristics are measured in terms of spectral characteristics and radiation patterns. The measured data are compared with calculations which predict controlled spontaneous emission in such structures. We find that the dominant effects on spontaneous emission in these thin layer structures are due to cavity controlled emission into allowed optical modes and stress induced dipole orientation in the GaAs quantum well.

We report here the low-pressure metalorganic chemical vapor deposition growth of AlGaAs-GaAs quantum well heterostructures having low-temperature (4.2 K) photoluminescence spectra with full width at half-maximum (FWHM) values ranging from ≌6 to 4 meV for quantum wells having 6–28 monolayer (ML) widths, respectively. These linewidths are compared to those measured for quantum wells grown by molecular beam epitaxy, flow-rate modulation epitaxy, and atomic layer epitaxy. We find that the FWHM values for the thinnest quantum wells grown in the present study (≌6 ML) are equal to or narrower than those observed for comparable structures produced by other technologies.