At high temperature, infra-red focal plane arrays are limited by their performance in operability, detectivity D * or noise equivalent temperature difference. Trap characterization and defect studies are necessary to better understand these limitations at high temperature. In this paper, we use deep level transient spectroscopy to study electrically active defects in mercury cadmium telluride n +/p diodes. The material investigated has a cut-off frequency (λ c) of 2.5 μm at 180 K and p doping performed with mercury vacancy. Trap energy signatures as well as capture cross-section measurements are detailed. A low temperature hole trap close to midgap is observed in the range 150–200 K with an activation energy around 0.18 ± 0.025 eV. A high temperature hole trap is also observed in the range 240–300 K with an activation energy of 0.68 ± 0.06 eV. A hole capture cross-section of 10−19 cm2 is obtained for both traps. The nature of the defects and their correlation with dark current are discussed.

HgCdTe has been shown to be the first semiconductor exhibiting single-carrier multiplication in avalanche photodiodes (APDs) up to multiplication factors larger than 1000 and with close to zero excess noise. These results have opened a new horizon for low-flux and/or versatile imaging from visible wavelengths up to the infrared cutoff wavelength of the APDs. In this paper we report the first results on mid-wave infrared (MWIR) cutoff wavelength APDs manufactured at Sofradir in collaboration with CEA-LETI. These APDs display high gain and low dispersion on and between wafers. In particular, a record avalanche gain M of over 10,000 is observed for some diode structures. This result provides an additional demonstration of the stability of single-carrier multiplication in HgCdTe and shows that the technological processes used at Sofradir are well adapted to APD manufacturing. A dedicated readout integrated circuit (ROIC) with 384 × 288 format and l5 μm pitch was developed to address both passive amplified imaging and active laser-assisted imaging. Arrays were produced using p-type HgCdTe films grown by liquid-phase epitaxy on CdZnTe substrates. Focal-plane array (FPA) performance is reported for ROICs hybridized with APD arrays manufactured at Sofradir. Operability of the best devices exceeds 99.7% for gains up to 55. Relative dispersions of the gain and ROIC output voltage are lower than 4%. The excess noise factor is lower than 1.4 over this range of gains.

Thermionic emission current in heterostructures can be used to enhance thermoelectric properties beyond what can be achieved with conventional bulk materials. The Bandgap discontinuity at the junction between two materials is used to selectively emit hot electrons over a barrier layer from cathode to anode. This evaporative cooling can be optimized at various temperatures by adjusting the barrier height and thickness. Theoretical and experimental results for nonisothermal thermionic emission in heterostructures are presented. Single stage InGaAsP-based heterostructure integrated thermionic (HIT) coolers are fabricated and characterized. Cooling on the order of a degree over one micron thick barriers has been observed. Nonisothermal transport in highly doped tall barrier superlattices is also investigated. An order of magnitude improvement in cooling efficiency is predicted for InAlAs/InP superlattices.

Monolithic widely-tunable transmitters are key enablers in reducing the component size, power consumption, and simplifying DWDM network provisioning. We discuss design and performance of monolithic transmitters based on SGDBR laser and electroabsorption or Mach-Zehnder modulators.

Tunable semiconductor lasers have been listed in numerous critical technology lists for future optical communication systems. Lasers with full band tuning ranges (C or L) allow reduction of the inventory cost and simplify deployment and operation of existing systems in addition to enabling wavelength agile networking concepts in future systems. Furthermore, monolithic integration of full band tunable lasers with modulators to form complete transmitters offers the most potential for reducing system size, weight, power consumption, and cost. This paper summarizes design, fabrication technology, and performance characteristics of widely tunable CW sources and transmitters based on chip scale integration of a Sampled Grating Distributed Bragg Reflector (SG DBR) laser with a Semiconductor Optical Amplifier (SOA) and Electroabsorption (EA) or Mach Zehnder (MZ) modulator. Widely tunable CW sources based on SG-DBR lasers exhibit high fiber coupled output power (20 mW CW) and side mode suppression ratio (>40 dB), low relative intensity noise (below -140 dB/Hz) and line width (<5 MHz) across a 40 nm C-band tuning range. Characteristics of EA-modulated optical transmitters include fiber-coupled time-averaged powers in excess of 5 dBm, RF extinction ratios > 10 dB, and error-free transmission over 350 km of standard fiber at 2.5 Gb/s across a 40 nm tuning range. Monolithic integration of widely tunable lasers with MZ modulators allow for further extension of bit rate (10 Gb/s and beyond) and transmission distances through precise control of the transient chirp of the transmitter. Systematic investigations of accelerated aging confirm that reliability of these widely-tunable transmitters is sufficient for system deployment.

We have demonstrated a high-power widely tunable SG-DBR semiconductor laser monolithically integrated with a SOA. Chip power in excess of 55 mW and SMSR > 40 dB across a 40 nm tuning range have been achieved. Over 13 dBm fiber-coupled power was demonstrated across 85 50-GHz ITU L-band channels.

Highly efficient long wavelength vertical-cavity semiconductor optical amplifiers (VCSOAs) are presented. A carrier confining structure was introduced by etching mesas in the active region. The carrier confinement resulted in increased efficiency and amplifier gain. The efficiency was increased by a factor of 3 as compared to previous devices made from the same active region material. 17 dB fiber-to-fiber gain was measured and the internal gain was estimated to be 24 dB. This is the highest reported amplifier gain for a long wavelength VCSOA to date.

An InGaAsP multiquantum-well traveling-wave electroabsorption modulator is demonstrated with high extinction ratio and modulation efficiency. By designing a strain-compensated quantum-well active region with traveling-wave design, high saturation power (>14 dBm) for >20-GHz high-speed performance (1.5 dB drop at 20 GHz) is achieved. Due to high modulation efficiency (>30 dBN for 0 to 1 V 40-dB extinction ratio in 2 V), error free 10-Gb/s operation with 1 V/sub p-p/ driving voltage is obtained. By comparing codirections and counterdirections of optical and microwave interactions, pulse generation at 40 GHz shows that the traveling-wave performance has an advantage for short pulses with high-power output, where pulsewidth as short as 4.5 ps is obtained in this kind of device.

We report on the fabrication and operation of the first electrically pumped 1.55m vertical-cavity laser array for wavelength-division-multiplexing applications. The array consisted of four channels operating between 1509 and 1524 nm. Wafer bonding was used to integrate GaAs–AlGaAs distributed Bragg reflectors with an InP–InGaAsP active region.

Metalorganic chemical vapor deposition (MOCVD) is a promising technology for the growth of epitaxial semiconductors. It has traditionally lacked real-time growth monitoring and control, which limits the precise reproducibility needed for high performance devices. Two complementary control approaches are investigated experimentally. The first is a feedforward disturbance rejection strategy using ultrasonic concentration measurements to reject source gas bubbler disturbances. The second is a feedback system using an ultraviolet absorption sensor for real-time monitoring of reaction chamber gas concentrations. Postgrowth X-ray analysis of InP/GaInAs superlattice test devices is used to evaluate control system performance.

The first electrically pumped 1.55 mum multiple wavelength VCSEL array is demonstrated. The wafer bonded array consists of four channels operating between 1509 and 1574 nm. Multiple wavelengths were defined using an etched intracavity superlattice prior to bonding. Threshold currents of 0.9 mA and peak output powers of 0.45 mW were measured.

Single stage thin film coolers based on thermoelectric and thermionic cooling in p-type InGaAsP superlattice structures have been fabricated. Devices with different sizes and at various ambient temperatures have been characterized. Experimental results showed 0.5 degree centigrade cooling below the ambient temperature at 25C. This cooling over 1 4mu2m thick superlattice barrier corresponds to cooling power densities on the order of 200 W/cm2. The device cools by a factor of two better at higher temperatures (70C). This is due to the reduction of the superlattice thermal conductivity and the broadening of the electronic distribution function at higher temperatures. 150x150 micrometers 2 devices provide largest cooling at room temperature while the optimum device size shrinks as the temperature increases. Simulations results that take into account finite thermal resistance of the InP substrate, the effect of the contact resistance, heat generation in the wire-bonds and metallic pads on top of the device predict accurately the optimum cooling of these micro refrigerators. By eliminating the major parasitic sources of heating (Joule heating in the substrate, heat conduction through the side contact and reducing the contact resistance to 5x7-7 ohm-cm2) simulations show that, ultimately, one can achieve 15 degree(s)C cooling (10's of kW/cm2 cooling power) with single stage p-InGaAsP thin film coolers.

We report on the fabrication and operation of the first electrically pumped 1.55-/spl mu/m vertical-cavity laser array for wavelength-division-multiplexing applications. The array consisted of four channels operating between 1509 and 1524 nm. Wafer bonding was used to integrate GaAs-AlGaAs distributed Bragg reflectors with an InP-InGaAsP active region.

The modulation/switching properties of a vertical-cavity semiconductor optical amplifier operating at 1.3 mum wave, length are investigated. The device was optically pumped and operated in reflection mode. A 150-mV (100 mA) modulation of the drive to the pump source produced a 7-dB modulation of the pump power, which produced a 35-dB modulation in the output signal. The maximum extinction ratio was 35 dB, and limited by device heating. Frequency response measurements revealed a modulation bandwidth of 1.8 GHz when the amplifier was saturated. This enabled 2.5-Gb/s modulation of a -10 dBm input signal with 5.5-dB fiber-to-fiber gain.

The switching/modulation properties of a vertical-cavity semiconductor optical amplifier (VCSOA) are investigated. We report on maximum extinction ratio, carrier recombination lifetime, and modulation bandwidth of an optically pumped VCSOA operated in reflection mode. A 35dB output signal extinction ratio was measured for a 7dB pump power modulation. The carrier recombination lifetime was investigated by short pulse optical pumping and detection by means of a streak camera. The extinction ratio analysis and the measured carrier lifetime suggests switching times on the order of 10ps. Frequency response measurements revealed a modulation bandwidth of 1.8GHz for operation in the saturated regime.