ABSTRACT A quick and reliable method to estimate the channel temperature of GaN high electron mobility transistors is extremely important in order to understand the physical degradation mechanisms as well as to extract a meaningful life... more
ABSTRACT A quick and reliable method to estimate the channel temperature of GaN high electron mobility transistors is extremely important in order to understand the physical degradation mechanisms as well as to extract a meaningful life time of the device. In this work, we present a simple yet powerful method to electrically measure the channel temperature of GaN HEMTs with a synchronized pulsed I-V setup. To validate the technique, we extract thermal resistance a) on the same device, multiple times, b) on multiple identical devices on the same wafer, c) on devices with different geometries and d) on identical devices with different level of degradation.
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Summary form only given. Several applications such as free space communication, laser radar, and night vision require a single mode, single-frequency laser with an optical power of /spl sim/1 W and a wavelength of 1.55 /spl mu/m.... more
Summary form only given. Several applications such as free space communication, laser radar, and night vision require a single mode, single-frequency laser with an optical power of /spl sim/1 W and a wavelength of 1.55 /spl mu/m. Recently, high power InGaAsP-InP tapered lasers were obtained at this wavelength with a single lateral mode, but still with numerous longitudinal modes. Here, we report on a high-power tapered AlGaInAs-InP distributed Bragg reflector (DBR) tapered single frequency laser.
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Vertical-cavity surface-emitting lasers (VCSELs) have recently become available commercially, finding many uses in data communication systems (with an emission wavelength near 850 nm), printers (in the visible region), compact disk... more
Vertical-cavity surface-emitting lasers (VCSELs) have recently become available commercially, finding many uses in data communication systems (with an emission wavelength near 850 nm), printers (in the visible region), compact disk players (near 780 nm) and many other systems. VCSELs may also find many applications in data communication and telecommunication systems (at 1.3 μm and 1.55 μm); however, they are not yet available commercially in this wavelength range. These wavelengths are of great interest for the transmission of information over fibers. Longer distances and higher speeds dictate the move toward these wavelengths, which correspond to the minimum dispersion and minimum loss in standard glass fiber at 1.3 and 1.55 μm, respectively.
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A simple thin film effective index analysis for first-order gratings in Si photonic waveguides is shown to provide highly accurate results for reflected and transmitted power spectrums as long as the waveguide remains single mode and... more
A simple thin film effective index analysis for first-order gratings in Si photonic waveguides is shown to provide highly accurate results for reflected and transmitted power spectrums as long as the waveguide remains single mode and non-radiating. A cover layer can be added to the grating region of a Si photonic waveguide to increase the strength of the grating, modify transition losses from the input waveguide to the grating waveguide region, and/or modify the width of the reflectivity spectrum. For a given grating period, the peak reflection and spectral width of the reflectivity decrease as the duty cycle is decreased or increased from ~50%. For both radiating and multimode structures, the coupling between all modes, power radiated towards the superstrate (upwards), power radiated downwards (substrate) and transmitted power analyzed by Floquet-Bloch, Eigenmode Expansion and Finite Difference Time Domain methods show excellent agreement. Coupling coefficients calculated using an...
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A quick andreliable methodtoestimate thechannel temperature ofGaNhighelectron mobility transistors isextremely important inorder tounderstand thephysical degradation mechanisms aswellastoextract ameaningful life timeofthe device. Inthis... more
A quick andreliable methodtoestimate thechannel temperature ofGaNhighelectron mobility transistors isextremely important inorder tounderstand thephysical degradation mechanisms aswellastoextract ameaningful life timeofthe device. Inthis work, wepresent asimple yetpowerful method toelectrically measurethechannel temperature ofGaN HEMTswithasynchronized pulsed I-Vsetup. Tovalidate the technique, weextract thermal resistance a)onthesamedevice, multiple times, b)onmultiple identical devices onthesame wafer, c)ondevices withdifferent geometries andd)onidentical devices withdifferent level ofdegradation.
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Bent waveguides have been used for many years to provide lateral guiding in semiconductor lasers. Since the simple effective index method applied to the bent waveguide structure is at best an estimation, we have applied the beam... more
Bent waveguides have been used for many years to provide lateral guiding in semiconductor lasers. Since the simple effective index method applied to the bent waveguide structure is at best an estimation, we have applied the beam propagation method and the finite difference method to this problem. Our preliminary findings qualitatively agree with the effective index predictions: for a uniform
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Strained multiple quantum wells (MQW) AlGaInAs and InGaAsP ridge-guide lasers operating at 1.3 μm are fabricated by using the same process. The comparative investigation shows that AlGaInAs lasers present superior performance in relation... more
Strained multiple quantum wells (MQW) AlGaInAs and InGaAsP ridge-guide lasers operating at 1.3 μm are fabricated by using the same process. The comparative investigation shows that AlGaInAs lasers present superior performance in relation to InGaAsP lasers. The characteristic temperature T0 for the AlGaInAs lasers, ~100 K, is twice that of the InGaAsP lasers, ~500 K, resulting in substantially lower threshold
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Summary form only given. Several applications such as free space communication, laser radar, and night vision require a single mode, single-frequency laser with an optical power of ~1 W and a wavelength of 1.55 μm. Recently, high power... more
Summary form only given. Several applications such as free space communication, laser radar, and night vision require a single mode, single-frequency laser with an optical power of ~1 W and a wavelength of 1.55 μm. Recently, high power InGaAsP-InP tapered lasers were obtained at this wavelength with a single lateral mode, but still with numerous longitudinal modes. Here, we report on a high-power tapered AlGaInAs-InP distributed Bragg reflector (DBR) tapered single frequency laser
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ABSTRACT AlGaInAs semiconductor lasers operating at a wavelength of 1.3 micrometers show superior performance compared to InGaAsP lasers. Ridge guide lasers are fabricated from both material systems by the same process. The characteristic... more
ABSTRACT AlGaInAs semiconductor lasers operating at a wavelength of 1.3 micrometers show superior performance compared to InGaAsP lasers. Ridge guide lasers are fabricated from both material systems by the same process. The characteristic temperature To for the AlGaInAs lasers (approximately 100 degree(s)K) is about twice that of the InGaAsP lasers (approximately 50 degree(s)K) resulting in substantially lower thresholds (approximately 34 mA compared to approximately 56 mA) at 85 degree(s)C. The 3-dB modulation frequency of AlGaInAs lasers is about 25% higher than that of the InGaAsP lasers.
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The InGaAsP/InP material system has a large conduction band offset ((Delta) Ec equals 0.72 (Delta) Eg which provides strong electron confinement and prevents carrier overflow under high temperature operation. Therefore, AlGaInAs/InP... more
The InGaAsP/InP material system has a large conduction band offset ((Delta) Ec equals 0.72 (Delta) Eg which provides strong electron confinement and prevents carrier overflow under high temperature operation. Therefore, AlGaInAs/InP lasers have better performance at high temperature operation.
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Thermal assessment of AlGaN/GaN heterostructure on diamond substrate is presented. To emphasize the advantages of diamond substrate for GaN, results of test devices on GaN-on-Diamond material are compared to those on GaN-on-SiC and... more
Thermal assessment of AlGaN/GaN heterostructure on diamond substrate is presented. To emphasize the advantages of diamond substrate for GaN, results of test devices on GaN-on-Diamond material are compared to those on GaN-on-SiC and GaN-on-Si materials. Mesa resistors and High Electron Mobility Transistors (HEMTs) fabricated using a 0.25 μm gate length process are characterized. Infrared thermography is employed for measurement of temperature rise in the test resistors and transistors at different power dissipation conditions. Addition of a simple feature to the conventional mesa resistor is found to allow a non-destructive, on-wafer compatible and more reliable surface temperature determination using IR thermography. DC current-voltage characteristics are included to show the impact of different substrates on the electrical behavior of HEMTs. Our results clearly demonstrate a significant thermal advantage of diamond substrate compared to SiC and Si substrate for GaN HEMTs designed for closely comparable electrical performance. For the same average channel temperature rise in the identical HEMTs, we estimate that GaN-on-Diamond material used in this study allows 1.7X dissipated power of GaN-on-SiC and 3X dissipated power of GaN -on-Si.
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ABSTRACT In this paper we report the observation of spikes in the intensity power spectra of strained- layer multiple quantum well lasers emitting at wavelengths of 1.3 micrometers and 1.5 micrometers . The spacing between the spikes on... more
ABSTRACT In this paper we report the observation of spikes in the intensity power spectra of strained- layer multiple quantum well lasers emitting at wavelengths of 1.3 micrometers and 1.5 micrometers . The spacing between the spikes on fiber-pigtailed lasers was equal to the mode spacing of the fiber resonator (Delta) (nu) fiber equals c/(2 NgL) where c is the speed of light, Ng is the group index, and L is the length of the fiber.
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We report excellent low-voltage (5 to ~ 10 V drain bias) microwave and millimeter-wave performance of deeply scaled InAn/AlN/GaN devices with field-plate gate of ~ 50-nm length, MBE regrown ohmic contacts, and sub-500-nm S-D spacing on... more
We report excellent low-voltage (5 to ~ 10 V drain bias) microwave and millimeter-wave performance of deeply scaled InAn/AlN/GaN devices with field-plate gate of ~ 50-nm length, MBE regrown ohmic contacts, and sub-500-nm S-D spacing on four different wafers. These four wafers include also T-gate (no field-plate) devices with very thin passivation and smaller gate (~ 30 nm), which had (for reference) high fT/fmax of ~270/230 GHz, respectively, both for D- and E-mode devices. Their counterparts with field-plate gates (same gate geometry but with underlying dielectric) and 50-nm gates had lower fT/fmax but excellent performances at 10 GHz with up to 67%-69% power-added efficiency (PAE) at 6 V bias and 30 GHz with up to 14.4 dB associated gain and 2.6 W/mm and 39.6% PAE at 8 V bias. The noise figure of these devices at 10 GHz was ~ 0.25 dB with 3 V drain bias. We have measured the linearity [third-order intercept (TOI)] of 300- μm devices on another wafer with 90-nm field-plate gates: at 5 GHz and 5 V bias the devices had 31-dBm TOI with 0.31 W/mm, 18.5-dB gain, and 27.1% PAE.
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Research Interests:
ABSTRACT We report 1000-transistor-level monolithic circuit integration of sub-30-nm gate-recessed E/D GaN high-electron-mobility transistors with fT and fmax above 300 GHz. Simultaneous fT/fmax of 348/340 and 302/301 GHz for E- and... more
ABSTRACT We report 1000-transistor-level monolithic circuit integration of sub-30-nm gate-recessed E/D GaN high-electron-mobility transistors with fT and fmax above 300 GHz. Simultaneous fT/fmax of 348/340 and 302/301 GHz for E- and D-mode devices, respectively, was measured, representing a 58% increase in fT compared with our previous report, due to improved management of RC parasitic delay. Three-terminal E- and D-mode breakdown voltage of 10.7 and 11.8 V, respectively, is limited by gate-drain breakdown.
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ABSTRACT Record RF performance of AlGaN/GaN high electron mobility transistors (HEMTs) on a diamond substrate with over 7 W/mm output power density at 10 GHz is reported. It is achieved along with the peak power-added-efficiency over 46%... more
ABSTRACT Record RF performance of AlGaN/GaN high electron mobility transistors (HEMTs) on a diamond substrate with over 7 W/mm output power density at 10 GHz is reported. It is achieved along with the peak power-added-efficiency over 46% and power gain over 11 dB for 2 × 100 μm gate-width HEMTs at 40 V drain bias. Device wafers are prepared by first removing the host Si (111) substrate and nitride transition layers beneath the channel, depositing a 50 nm dielectric onto the exposed GaN buffer, and finally growing 100 μm of a chemical vapour deposition diamond onto the dielectric adhering to the epitaxial AlGaN/GaN. This approach enables the active GaN channel to be brought within 1 μm of the diamond substrate. Test HEMTs are fabricated using a dielectrically defined 0.25 μm gate length process.
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ABSTRACT The accuracy of different thermography techniques for the determination of AlGaN/GaN HEMT channel temperature was investigated. Micro-Raman thermography, a novel electrical testing method, and IR thermography were applied to... more
ABSTRACT The accuracy of different thermography techniques for the determination of AlGaN/GaN HEMT channel temperature was investigated. Micro-Raman thermography, a novel electrical testing method, and IR thermography were applied to measure the temperature in the active region of AlGaN/GaN HEMTs with different device geometries. Due to its accepted accuracy, micro-Raman thermography was performed on different devices in order to validate thermal simulation results. When compared to the validated thermal model, pulsed I-V measurements underestimated channel temperature to some degree, while IR thermography determined unrealistically low device temperatures.
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Page 1. HIGH-POWER SINGLE-FREQUENCY SEMICONDUCTOR LASERS Sandra R. Selniic, Susan L. Wilson, Gary A. Evans, Jay B. Kirk, Zuhair A. Alhilali, Duy Phan El. Eng. Dept., Southern Methodist University, POBox 750338, Dallas, TX 752 75 ...
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ABSTRACT
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AlGaInAs semiconductor lasers operating at a wavelength of 1.3 micrometers show superior performance compared to InGaAsP lasers. Ridge guide lasers are fabricated from both material systems by the same process. The characteristic... more
AlGaInAs semiconductor lasers operating at a wavelength of 1.3 micrometers show superior performance compared to InGaAsP lasers. Ridge guide lasers are fabricated from both material systems by the same process. The characteristic temperature To for the AlGaInAs lasers (approximately 100 degree(s)K) is about twice that of the InGaAsP lasers (approximately 50 degree(s)K) resulting in substantially lower thresholds (approximately 34 mA compared to approximately 56 mA) at 85 degree(s)C. The 3-dB modulation frequency of AlGaInAs lasers is about 25% higher than that of the InGaAsP lasers.
Research Interests:
In this paper we report the observation of spikes in the intensity power spectra of strained- layer multiple quantum well lasers emitting at wavelengths of 1.3 micrometers and 1.5 micrometers . The spacing between the spikes on... more
In this paper we report the observation of spikes in the intensity power spectra of strained- layer multiple quantum well lasers emitting at wavelengths of 1.3 micrometers and 1.5 micrometers . The spacing between the spikes on fiber-pigtailed lasers was equal to the mode spacing of the fiber resonator (Delta) (nu) fiber equals c/(2 NgL) where c is the speed of light, Ng is the group index, and L is the length of the fiber.
Research Interests:
Research Interests:
Research Interests:
ABSTRACT We present GaAs pHEMTs demonstrating output power over 1 W/mm in Ka-band at an operating voltage of 8 V. DC, RF and reliability results are reported. Continuous wave load pull tests at 35 GHz show peak power added efficiency of... more
ABSTRACT We present GaAs pHEMTs demonstrating output power over 1 W/mm in Ka-band at an operating voltage of 8 V. DC, RF and reliability results are reported. Continuous wave load pull tests at 35 GHz show peak power added efficiency of 52% and associated gain of 8 dB. The saturated output power of 1.2 W/mm is achieved. Power performance improvement is attributed to a new dielectrically defined 0.15 μm gate process which allows successful operation of these devices at a drain voltage of 8 V. Devices also show excellent small signal performance with maximum cut-off frequency as high as 107 GHz at a drain voltage of 1 V. Using three-temperature accelerated DC life tests, activation energy of 1.45 eV and median life time over 1 million hours at a channel temperature of 150°C are estimated.
Research Interests:
Research Interests:
A quick and reliable method to estimate the channel temperature of GaN high electron mobility transistors is extremely important in order to understand the physical degradation mechanisms as well as to extract a meaningful life time of... more
A quick and reliable method to estimate the channel temperature of GaN high electron mobility transistors is extremely important in order to understand the physical degradation mechanisms as well as to extract a meaningful life time of the device. In this work, we present a simple yet powerful method to electrically measure the channel temperature of GaN HEMTs with a synchronized pulsed I-V setup. To validate the technique, we extract thermal resistance a) on the same device, multiple times, b) on multiple identical devices on the same wafer, c) on devices with different geometries and d) on identical devices with different level of degradation.
Research Interests:
Research Interests:
ABSTRACT We present GaAs pHEMTs demonstrating output power over 1 W/mm in Ka-band at an operating voltage of 8 V. DC, RF and reliability results are reported. Continuous wave load pull tests at 35 GHz show peak power added efficiency of... more
ABSTRACT We present GaAs pHEMTs demonstrating output power over 1 W/mm in Ka-band at an operating voltage of 8 V. DC, RF and reliability results are reported. Continuous wave load pull tests at 35 GHz show peak power added efficiency of 52% and associated gain of 8 dB. The saturated output power of 1.2 W/mm is achieved. Power performance improvement is attributed to a new dielectrically defined 0.15 μm gate process which allows successful operation of these devices at a drain voltage of 8 V. Devices also show excellent small signal performance with maximum cut-off frequency as high as 107 GHz at a drain voltage of 1 V. Using three-temperature accelerated DC life tests, activation energy of 1.45 eV and median life time over 1 million hours at a channel temperature of 150°C are estimated.
Research Interests:
Research Interests:
A quick and reliable method to estimate the channel temperature of GaN high electron mobility transistors is extremely important in order to understand the physical degradation mechanisms as well as to extract a meaningful life time of... more
A quick and reliable method to estimate the channel temperature of GaN high electron mobility transistors is extremely important in order to understand the physical degradation mechanisms as well as to extract a meaningful life time of the device. In this work, we present a simple yet powerful method to electrically measure the channel temperature of GaN HEMTs with a synchronized pulsed I-V setup. To validate the technique, we extract thermal resistance a) on the same device, multiple times, b) on multiple identical devices on the same wafer, c) on devices with different geometries and d) on identical devices with different level of degradation.