- As a serial entrepreneur, inventor, and engineer, I bring a robust business acumen coupled with deep technical expert... moreAs a serial entrepreneur, inventor, and engineer, I bring a robust business acumen coupled with deep technical expertise. My specializations lie in opto-electronics and wireless communications, complemented by extensive experience in semiconductors, healthcare, enterprise software, and logistics.My career spans multiple continents, having worked across Asia (Japan, China, Korea, Taiwan), Africa, and Central America. This global exposure has honed my ability to navigate diverse business environments and technological landscapes.With a track record of innovation and a knack for identifying market opportunities, I leverage my technical knowledge and business insight to drive forward-thinking solutions in rapidly evolving industries.edit
Responsivity and thermionic dark current are studied in asymmetric stepped GaAs/AlGaAs multiquantum well infrared detectors with a single bound state. Although attributed to different transport properties, both the photoexcited and the... more
Responsivity and thermionic dark current are studied in asymmetric stepped GaAs/AlGaAs multiquantum well infrared detectors with a single bound state. Although attributed to different transport properties, both the photoexcited and the thermally emitted carriers exhibit asymmetric transport properties with respect to the voltage polarity. The experimental characteristics are explained by the minibands-quasi continuum energy structure above the barrier.
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We experimentally demonstrate the operation of a fully integrated optoelectronic circuit with optical input and output consisting of a p-i-n photodetector and load resistor, a depletion mode GaAs-AI,Ga, - ,As heterostructure field effect... more
We experimentally demonstrate the operation of a fully integrated optoelectronic circuit with optical input and output consisting of a p-i-n photodetector and load resistor, a depletion mode GaAs-AI,Ga, - ,As heterostructure field effect transistor (HFET) and self-biased HFET load, together with an output GaAs-AI,Ga, - ,As multiple quantum-well optical mod- ulator. All elements have been monolithically integrated within a 50 x 50 pm area. A low optical power input causes a modula- tion of a higher power output, demonstrating optical signal amplification.
ABSTRACT An in situ process which includes electron cyclotron resonance plasma etching and molecular beam epitaxial regrowth is applied to the fabrication of buried heterostructure vertical cavity surface‐emitting laser (SEL) diodes and... more
ABSTRACT An in situ process which includes electron cyclotron resonance plasma etching and molecular beam epitaxial regrowth is applied to the fabrication of buried heterostructure vertical cavity surface‐emitting laser (SEL) diodes and edge‐emitting laser (EEL) diodes. The buried SEL with a 7.5 μm diameter has a pulsed laser threshold current of 1 mA, and a threshold voltage of 4 V with a peak power of 0.9 mW. The buried EEL with 2.5 μm stripe width and 800 μm cavity length has a threshold current density of 500 A/cm2.
Research Interests: Materials Engineering, Aerospace Engineering, Molecular beam epitaxy, Organic Semiconductor Laser, Atmospheric sciences, and 10 moreVertical Cavity Surface Emitting Laser, Plasma Etching, Current Density, Gallium Arsenide, Peak Power, Laser Diode, Light Emitting Diode, Threshold Voltage, Buried Heterostructure Lasers, and Electron Cyclotron Resonance Heating
There is an ever increasing role for III-V alloys in semiconductor technology. Currently, III-V compounds are used or have been developed for use as light-emitting diodes (LED), heterojunction lasers, photo diodes, solar cells, infrared... more
There is an ever increasing role for III-V alloys in semiconductor technology. Currently, III-V compounds are used or have been developed for use as light-emitting diodes (LED), heterojunction lasers, photo diodes, solar cells, infrared detectors, high electron mobility transistors, and very large scale integration (VLSI). As the quest for new devices and improvements on current devices continues, it is necessary to examine the effects of processing the starting materials and on the devices. An often used processing step requires thermal treatment. The author conducted numerous studies on GaAs epitaxial materials grown by Liquid Phase and Molecular Beam Epitaxial techniques. Epitaxial layers of carrier concentration ranging from 10¹â´â»Â¹Â°sup 17/ cmâ»Â³ were thermally treated at temperatures from 700°C to 950°C for thirty (30'') minutes. The thermal treatment involved capped and uncapped samples. The treated layers were characterized via conventional Hall Measurements, Capacitance-Voltage, Photoluminescence (PL) and Deep level transient spectroscopy (DLTS) measurements.
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Abstract A 50 Mbits/sec burst-mode transceiver (TRx) has been demonstrated that uses a small, integrated optical module. The design of this TRx has potential in realizing a low cost module that will be suitable for the access telecom... more
Abstract A 50 Mbits/sec burst-mode transceiver (TRx) has been demonstrated that uses a small, integrated optical module. The design of this TRx has potential in realizing a low cost module that will be suitable for the access telecom networks
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Abstract We report the first observation of bistable polarization switching in a vertical cavity surface-emitting GaAs/AlGaAs laser (VCSEL) under optical injection. Input wavelength dependence of the switching is studied. Polarization... more
Abstract We report the first observation of bistable polarization switching in a vertical cavity surface-emitting GaAs/AlGaAs laser (VCSEL) under optical injection. Input wavelength dependence of the switching is studied. Polarization switching at frequencies up to 6 GHz ...
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ABSTRACT Although there has been extensive research1–8 on multi-quantum well infrared photodetectors (QWIPs), which typically contain many (~50) periods, there has been relatively limited experimental work9–11 (using a fixed frequency CO2... more
ABSTRACT Although there has been extensive research1–8 on multi-quantum well infrared photodetectors (QWIPs), which typically contain many (~50) periods, there has been relatively limited experimental work9–11 (using a fixed frequency CO2 laser) done on QWIPs containing only a single quantum well. Recently, we have performed a complete series of experiments12–14 on single quantum well structures with n-type doped well, p-type doped well and un-doped well. These doped-single well detectors are, in fact, particularly interesting since they have exceptionally high optical gain compared to multi well detectors. The optical response of the undoped single quantum well detector is strongly dependent on the bias voltage because the well is filled by tunneling through a thin emitter barrier. In addition, their simple band structures allow accurate calculations of the bias voltage dependence of the potential profiles of each of the two barriers, band bending effects in the contacts, as well as charge accumulation (or depletion) in the quantum well. Therefore by comparing theory with experiment, one can achieve a better overall understanding of the optical and transport physics in these quantum well infrared photodetectors.
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Expanding interest in large-scale fabrication of electronic and photonic devices and in the scale-up of epitoxial growth reactors is creating the need for high quality large diameter InP substrate material. This paper will discuss the... more
Expanding interest in large-scale fabrication of electronic and photonic devices and in the scale-up of epitoxial growth reactors is creating the need for high quality large diameter InP substrate material. This paper will discuss the evaluating of three-inch diameter semi-insulating Fe-doped InP substrate material purchased from two commercial suppliers. The results of Photon Back Scatter, Infrared Transmission Microscopy, Hall Effect, and Spatially Resolved Photoluminescence measurements will be presented and evaluated.
ABSTRACTChanges in the electronic properties of bulk GaAs crystals, grown from melts of varied As:Ga ratios, and Si-donor concentrations, were investigated by annealing in the temperature range 850°C to 1050°C. We found a gradual... more
ABSTRACTChanges in the electronic properties of bulk GaAs crystals, grown from melts of varied As:Ga ratios, and Si-donor concentrations, were investigated by annealing in the temperature range 850°C to 1050°C. We found a gradual reduction of the free carrier concentration, a corresponding decrease in the luminescence spectral intensity, and a suppression of the near band-edge peaks with annealing time at any temperature. Deep level and impurity concentrations remained essentially constant. The magnitude of these changes was found to be determined predominantly by the annealing time and temperature, and the starting composition of the material We argue for a non-radiative native acceptor defect, or defect complex, forming during the annealing cycle. We present here the thermodynamic interpretation for this behavioi in terms of point defect equilibria.
ABSTRACT Vertical cavity zone lasers (Z-lasers) operating at 980 nm and 850 nm have been fabricated. This new class of high power (>100 mW) high efficiency (η≈ 36%) large area (70 μm diameter) vertical cavity laser has... more
ABSTRACT Vertical cavity zone lasers (Z-lasers) operating at 980 nm and 850 nm have been fabricated. This new class of high power (>100 mW) high efficiency (η≈ 36%) large area (70 μm diameter) vertical cavity laser has an output that is automatically focused to a spot at a particular distance away from the laser. This is in contrast to the conventional surface or edge emitting array devices that usually have multiple far-field lobes and need external optical components for focusing purposes. Among other applications, the unique properties of 980 nm Z-lasers makes them attractive as a pump laser for fiber amplifier systems
ABSTRACT Vertical cavity zone lasers (Z-lasers) operating at 980 nm have been fabricated for the first time. This new class of high power (>100 mW) high efficiency (ηext≈36%) large area (70 μm diameter) vertical cavity... more
ABSTRACT Vertical cavity zone lasers (Z-lasers) operating at 980 nm have been fabricated for the first time. This new class of high power (>100 mW) high efficiency (ηext≈36%) large area (70 μm diameter) vertical cavity laser has an output that is automatically focused to a spot at a particular distance away from the laser. This is in contrast to the conventional surface or edge emitting array devices that usually have multiple far-field lobes and need external optical components for focusing purposes
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ABSTRACTDLTS measurements are used to detect and identify the interstitial related defects in n-type silicon. The materials dependences of the reactions of the [E(0.12), H(O.27)], [ME(0.30), ME(0.29), ME(0.23), ME(0.21)], ]ME(0.10),... more
ABSTRACTDLTS measurements are used to detect and identify the interstitial related defects in n-type silicon. The materials dependences of the reactions of the [E(0.12), H(O.27)], [ME(0.30), ME(0.29), ME(0.23), ME(0.21)], ]ME(0.10), ME(0.17)] and [H(0.36)] spectral features lead to their identification as representing the two charge states of Ci, the multistable configurations of Ps-Ci, the bistable Cs-Sii-Cs, and the Ci-Oi defects, respectively. The branching ratios for the reactions of interstitial carbon with the impurities are given.
A possible laser device is designed with the use of classically free quasibound electron states. An asymmetric semiconductor electron wave Fabry-Perot interference filter is designed with an upper electron state having much stronger... more
A possible laser device is designed with the use of classically free quasibound electron states. An asymmetric semiconductor electron wave Fabry-Perot interference filter is designed with an upper electron state having much stronger confinement (235f6 lifetime) than the lower electron state (76f s lifetime). This structure also allows for direct current pumping of the upper state and rapid depletion of
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ABSTRACTAdvances in epitaxial growth techniques such as molecular beam epitaxy and metal organic chemical vapor deposition have facilitated the formation of high quality III-V heterostructures with dimensional control down to atomic... more
ABSTRACTAdvances in epitaxial growth techniques such as molecular beam epitaxy and metal organic chemical vapor deposition have facilitated the formation of high quality III-V heterostructures with dimensional control down to atomic levels, with abrupt doping and near-defect-free interfaces. The flexibility and remarkable control offered by these techniques have resulted in the fabrication of new devices based on confinement or modulation of carriers in thin III-V heterostructures. Quantum wells and superlattice based devices are expected to be utilized in optical information processing as sources, modulators, and detectors. In this paper, we will review the general epitaxial requirements for quantum wells and superlattices based devices, and discuss the fabrication and properties of a new class of infrared photodetectors that employ intraband transitions in quantum wells.
The complexity and size of interconnection-rich telephone switching systems require the extension of data buses over a large complement of frames. Physical designers have chosen bit serial transport over fiber to overcome the length... more
The complexity and size of interconnection-rich telephone switching systems require the extension of data buses over a large complement of frames. Physical designers have chosen bit serial transport over fiber to overcome the length limitations of coaxial cable from attenuation, to reduce cable volume, to provide isolation and avoid ground loops, to reduce RFI and EMI interference and coupling between channels, and to be able to make and break live connections without damaging the transmitter or receiver electronics. It has been shown that for certain interconnection applications there exists an optimum degree of parallelism (based on cost), depending on the data rate and the number of the channels.1 Prototype one-dimensional optical data links (1D-ODL’s) using linear 1 × n device arrays have been demonstrated in a number of laboratories and take advantage of the current infrastructure of fiber ribbon, splices, and connectors. Extending this concept to a second dimension by creating a two-dimensional optical data link (2D-ODL) using n×m device arrays may yield further economies of scale. We have constructed several prototype 2D-ODL’s (Table 1 ) using direct modulation of 2D arrays of vertical-cavity surface-emitting lasers (VCSEL’s)2 as shown in Fig. 1, and symmetric self-electro-optic effect device (S-SEED) modulators3 with Si P-I-N/bipolar OEIC receivers.4 The benefits and drawbacks of each technology will be briefly discussed.
Vertical cavity surface emitting laser (VCSEL) technology has progressed rapidly over the past few years; however, Transverse Mode (TM) control remains elusive for VCSELS of practical dimensions.1-3 Here, we present a novel approach to... more
Vertical cavity surface emitting laser (VCSEL) technology has progressed rapidly over the past few years; however, Transverse Mode (TM) control remains elusive for VCSELS of practical dimensions.1-3 Here, we present a novel approach to select only the TEM00 lasing mode by using the exit window of a top surface4 emitter as a spatial filter. This technique allows us to produce repeatably and systematically TEM00-mode VCSELs exhibiting well-behaved electrical and optical characteristics, while maintaining the criteria of producibility. We also report record level single-TEM00-mode emission of over 2.6 mW.
ABSTRACT We report batch-processed, totally planar, vertical-cavity top surface emitting GaAs/AlGaAs laser devices and arrays. Different size devices are studied experimentally. We measure continuous-wave threshold currents down to 1.7 mA... more
ABSTRACT We report batch-processed, totally planar, vertical-cavity top surface emitting GaAs/AlGaAs laser devices and arrays. Different size devices are studied experimentally. We measure continuous-wave threshold currents down to 1.7 mA and output powers > 3.7 mW at room temperature. We also discuss interesting characteristics such as differential quantum efficiencies exceeding unity and multi-transverse mode behavior. An array having 64 X 1 individually-accessed elements is characterized and shown to have uniform room-temperature continuous-wave operating characteristics in threshold current approximately equals 2.1 +/- 0.1 mA, wavelength approximately equals 849.4 +/- 0.8 nm, and output power approximately equals 0.5 +/- 0.1 mW.
ABSTRACT Multiple transverse mode vertical cavity surface emitting lasers (MTM VCSEL) have been mostly overlooked as possible sources for optical communications. This is understandably so for applications that involve long haul... more
ABSTRACT Multiple transverse mode vertical cavity surface emitting lasers (MTM VCSEL) have been mostly overlooked as possible sources for optical communications. This is understandably so for applications that involve long haul transmission over single mode fiber where a narrow linewidth is an important parameter. But for data communication over short distances where multimode fiber is used, the potential of MTM VCSELs has not been explored. This talk presents the results of large signal modulation of an MTM VCSEL in a short fiber link at 1 Gb/s and 3 Gb/s
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ABSTRACT A possible laser device is designed with the use of classically free quasibound electron states. An asymmetric semiconductor electron wave Fabry-Perot interference filter is designed with an upper electron state having much... more
ABSTRACT A possible laser device is designed with the use of classically free quasibound electron states. An asymmetric semiconductor electron wave Fabry-Perot interference filter is designed with an upper electron state having much stronger confinement than the lower electron state. This structure also allows for direct current pumping of the upper state and rapid depletion of the lower state under the presence of a field. Spectroscopy experiments demonstrate the existence of the upper quasibound state in a test structure. This laser filter structure, designed for infrared gain with current pumping, is combined with a special injector filter for room temperature narrow energy current injection into the upper lasing state. A stack of 54 periods of this electrically pumped structure is placed within a waveguide geometry. A laser device is fabricated by etching mesa structures from 50 to 100 micrometers wide. End cleaved facets serve as reflectors for mesas from 2 to 5 mm long. Tests are performed on these devices to determine their electrical properties and suitability for lasing.
ABSTRACT A new type of asymmetric stepped GaAs/AlGaAs multi quantum well infrared detectors is reported. These asymmetric detectors utilize the usual bound to continuum transition. The current responsivity is remarkably asymmetric with... more
ABSTRACT A new type of asymmetric stepped GaAs/AlGaAs multi quantum well infrared detectors is reported. These asymmetric detectors utilize the usual bound to continuum transition. The current responsivity is remarkably asymmetric with regard to the voltage polarity. In contrast with rectangular wells, in which responsivity is saturated in both bias polarities, these wells exhibit saturation only for negative bias. The responsivity increases monotonously with positive electric field. The difference between polarities for the noise is much smaller at low temperatures. As a result, the highest D(superscript *) in positive polarity is much higher than in the negative one. This is attributed to changes induced by the field on the transport properties of the excited electrons. In particular, the bias affects the dwell time spent by the carrier wave packet in the well region. Employing this model, we achieve a very good fit with experimental data. The transport asymmetry is further studied using identical asymmetric wells which were grown in opposite sequences. It is shown that the effect of the asymmetry in the interfaces is of the same order of magnitude as the structural asymmetry.
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Compound semiconductors—semiconductors made when elements from Columns III and V of the Periodic Table are combined—are being used more frequently in the fabrication of integrated circuits. The evaluation and utilization of new processing... more
Compound semiconductors—semiconductors made when elements from Columns III and V of the Periodic Table are combined—are being used more frequently in the fabrication of integrated circuits. The evaluation and utilization of new processing technologies have enabled compound semiconductor technology to move out of the laboratory into real-world applications. Compound semiconductors, such as gallium arsenide and indium phosphide, are being used because of their inherent radiation hardness and their ability to quickly transmit electrons and because they can be utilized to make semiconductor lasers and photodetectors used in telecommunications. Although the raw chemical constituents used to make and process compound semiconductors have well-documented toxicological effects, compound semiconductor materials per se were not thought to present an acute toxicity hazard. This investigation documented the formation of arsine and phosphine—acutely toxic gaseous hydrides—which result from the handling and processing of gallium arsenide and indium phosphide. These data indicate that adequate precautions must be taken during almost all phases of gallium arsenide and indium phosphide processing as well as during procedures involving equipment maintenance.
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... infrared photodetectors BF Levine, A. Zussman, SD Gunapala, MT Asom, JM Kuo, and WS Hobson AT&T Bell Labomtorks, Murray Hdf, lieu Jersey 07974 (Received 6 April 1992; accepted for publication 13 July 1992) We present ...
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Tunneling emitter undoped quantum-well infrared photodetector. KMSV Bandara, BF Levine, and MT Asom AT&T Bell Laboratories, Murray Hill, New Jersey 07974 (Received 7 January 1993; accepted for publication 12 March 1993) ...... more
Tunneling emitter undoped quantum-well infrared photodetector. KMSV Bandara, BF Levine, and MT Asom AT&T Bell Laboratories, Murray Hill, New Jersey 07974 (Received 7 January 1993; accepted for publication 12 March 1993) ... Bandara, Levine, and Asom 347 Page 3. ...
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ABSTRACT We have fabricated high power carbon‐doped InGaAs/AlGaAs lasers using an impurity‐induced layer disordering process to define the active region. The advantage of carbon doping is that it exhibits significantly lower diffusivity... more
ABSTRACT We have fabricated high power carbon‐doped InGaAs/AlGaAs lasers using an impurity‐induced layer disordering process to define the active region. The advantage of carbon doping is that it exhibits significantly lower diffusivity compared to other p‐type dopants, thereby avoiding displacement of the p‐n junction, even at the high temperatures and long diffusion times required by the disordering process. Secondary ion mass spectrometry (SIMS) measurements before and after Si diffusion show the p‐n junction position to be unchanged during processing. The carbon was introduced using CCl 4 as an extrinsic precursor, giving improved control over doping levels and ternary growth conditions that is not available with intrinsic carbon doping. Thresholds of 20 mA and slope efficiencies of 0.44 mW/mA at 25 °C were obtained for lasers with cavity lengths of 500 μm and coated facets.
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... KMSV Bandara, BF Levine, RE Leibenguth, and MT Asom AT&T Bell Laboratories, Murray Hill, New Jersey 07974 (Received 7 January 1993; accepted for publication 14 April 1993) ... BF.Levine, A. Zussman, SD Gunapala, MT Asom,... more
... KMSV Bandara, BF Levine, RE Leibenguth, and MT Asom AT&T Bell Laboratories, Murray Hill, New Jersey 07974 (Received 7 January 1993; accepted for publication 14 April 1993) ... BF.Levine, A. Zussman, SD Gunapala, MT Asom, JM Kuo, and WS Hobson, J. Appl. Phys. ...