R. E. Leibenguth

GaAs MQW modulators integrated with silicon CMOS

We demonstrate integration of GaAs-AlGaAs multiple quantum well modulators to silicon CMOS circuitry via flip-chip solder-bonding followed by substrate removal. We obtain 95% device yield for 32/spl times/32 arrays of devices with 15 micron solder pads. We show operation of a simple circuit composed of a modulator and a CMOS transistor.<<ETX>>

Optical injection induced polarization bistability in vertical-cavity surface-emitting lasers

We report the observation of bistable polarization switching in a vertical‐cavity surface‐emitting laser under optical injection. The wavelength dependence of the switching is measured. It is found that this polarization switching is achieved through injection locking where both the wavelength and the polarization of the vertical‐cavity laser are locked to the injected optical signal.

Gain-dependent polarization properties of vertical-cavity lasers

We show that the partitioning of power into the two orthogonal eigen polarizations of infra-red gain-guided vertical cavity lasers depends upon the relative spectral overlap of the nondegenerate polarization cavity resonances with the laser gain spectrum. Furthermore, at the condition where the polarization resonances and the peak laser gain are aligned, abrupt switching of power between the eigen polarizations is observed as the gain sweeps through the polarization resonances. The gain-dependence of the polarization requires spectral splitting between the eigen polarizations, which is found to be strongly influenced by local strain. The polarization of the fundamental and higher-order spatial modes can be selected and maintained for all InGaAs vertical-cavity lasers in a wafer simply by employing a 20 nm or greater blue-shift offset of the peak laser gain relative to the cavity resonances. >

Control of vertical-cavity laser polarization with anisotropic transverse cavity geometries

We show the two-fold polarization degeneracy of etched air-post vertical-cavity surface emitting laser diodes can be lifted and a dominant polarization state selected through use of anisotropic transverse laser cavity geometries. For lasers with rhombus-shaped cavities, fundamental mode lasing emission linearly polarized along one specified crystal axis is obtained up to twice the threshold current. For dumbbell-shaped lasers, fundamental mode lasing emission linearly polarized along one specified crystal axis is maintained over the entire operating range of the device producing a maximum orthogonal polarization suppression ratio of 14 dB.<<ETX>>

In situ observations of misfit dislocation propagation in GexSi1−x/Si(100) heterostructures

We describe in situ electron microscrope observations of the motion of misfit dislocations in Ge0.3Si0.7/Si(100) heterostructures. A 350 A Ge0.3Si0.7/Si(100) structure is grown by molecular beam epitaxy at 550 °C. Although this is below the critical thickness for this composition and growth temperature, we observe misfit dislocation nucleation and propagation as a function of in situ annealing temperature in the electron microscope. This confirms the metastable nature of GeSi strained‐layer growth. The misfit dislocation density increases continuously with temperature, passing through an accelerated transition at ∼850 °C. We also report preliminary measurements of misfit dislocation velocity, which establish the identical relationship between threading and misfit dislocations in this system.We describe in situ electron microscrope observations of the motion of misfit dislocations in Ge0.3Si0.7/Si(100) heterostructures. A 350 A Ge0.3Si0.7/Si(100) structure is grown by molecular beam epitaxy at 550 °C. Although this is below the critical thickness for this composition and growth temperature, we observe misfit dislocation nucleation and propagation as a function of in situ annealing temperature in the electron microscope. This confirms the metastable nature of GeSi strained‐layer growth. The misfit dislocation density increases continuously with temperature, passing through an accelerated transition at ∼850 °C. We also report preliminary measurements of misfit dislocation velocity, which establish the identical relationship between threading and misfit dislocations in this system.

High‐power coherently coupled 8×8 vertical cavity surface emitting laser array

We demonstrate record high pulsed output power exceeding 530 mW from an electrically pumped phase‐coupled 8×8 vertical cavity surface emitting laser array (SELA) at room temperature. Three array types are compared: an 8×8 pixellated SELA(PSELA), an 8×8 grid contact SELA(CSELA), and a 78 μm×78 μm single broad area SEL(BSEL) emitter. The CSELA operating in a phase‐coupled supermode exhibits the lowest threshold current (100 mA) and voltage (1.6 V), highest damage threshold and a smooth L‐I characteristic with differential quantum efficiency ηd≳27%, the BSEL has the largest output power≳580 mW and a large ηd≳48%, the PSELA exhibited a large voltage with the largest ηd≳80%.

Top‐surface emitting lasers with 1.9 V threshold voltage and the effect of spatial hole burning on their transverse mode operation and efficiencies

The fabrication and operating characteristics of a 1.9 V top surface emitting laser are presented. A planar fabrication process with a modified ion implantation mask is used to achieve gain guided lasers operating up to 90 °C. The laser operates in the fundamental mode up to 0.7 mW with 3.2 mW total peak optical output power. Direct evidence of spatial hole burning for the fundamental and the next higher mode is observed. This spatial hole burning puts a limit on the fundamental mode operation and efficiency of the lasers.

GexSi1−x strained‐layer heterostructure bipolar transistors

Double heterostructure bipolar transistors with the base region consisting of a p‐Ge0.5Si0.5 strained‐layer superlattice have been grown by molecular beam epitaxy. At a wavelength of 1.3 μm, optical gain as high as 52 has been achieved in two‐terminal phototransistors. The large photocurrent is inferred to be a product of the transistor gain, on the order of 20, and avalanche multiplication. A differential current gain of 10 has been obtained in the three‐terminal bipolar transistors. The incorporation of a narrow band‐gap GexSi1−x superlattice base is expected to result in higher emitter injection efficiency as compared to Si bipolar transistors.

Improved performance of quantum well infrared photodetectors using random scattering optical coupling

We demonstrate that a random scattering reflector on top of a quantum well infrared photodetector increases the optical coupling (i.e., increases the infrared absorption, responsivity, and detectivity) by an order of magnitude compared with a one‐dimensional grating or 45° angle of incidence geometry.

Batch fabrication and operation of GaAs-Al/sub x/Ga/sub 1-x/As field-effect transistor-self-electrooptic effect device (FET-SEED) smart pixel arrays

The structure, processing, and performance of arrays of integrated field-effect transistor-self-electrooptic effects devices (FET-SEEDs) consisting of doped-channel field-effect transistors, multiple quantum-well (MQW) modulators, and p-i-n MQW detectors are discussed. The performance of the FETs and SEEDs such as g/sub m/ and contrast, is equivalent to that obtained when they are made separately. Typical values are g/sub m/=80 mS/mm and contrast of 3. The largest arrays contain 128 circuits. The circuits operate at speeds as fast as 500 Mb/s, with optical input switching energy of approximately=400 fJ. At 170 Mb/s, the required optical input switching energy is approximately=70 fJ. This optical energy is at least a factor of 20 less than for symmetric SEEDs (S-SEEDs) with the same optical window sizes. Hence, FET-SEEDs provide superior performance compared to conventional S-SEEDs. >