2016 11th European Microwave Integrated Circuits Conference (EuMIC), 2016
In this paper, we report anomaly and intrinsic capacitance behaviour over temperature of AlGaN/Ga... more In this paper, we report anomaly and intrinsic capacitance behaviour over temperature of AlGaN/GaN/SiC and AlGaAs/GaAs high electron mobility transistors using on wafer measurement up to 50 GHz. Differences are observed; most notably that the trend of the intrinsic capacitances behaviour with temperature of the two device technologies are completely different. This anomaly continues for the other device parameter such as threshold voltage, two-dimension electro gas sheet carrier densities as well. These results are valuable for the future design optimizations of the advanced GaN and GaAs based monolithic microwave integrated circuit operating at high frequency and temperature.
... W. Schrenk, G. Strasser, and D. Pogany are with the Vienna University of Technology, 1040 Vie... more ... W. Schrenk, G. Strasser, and D. Pogany are with the Vienna University of Technology, 1040 Vienna, Austria (e-mail: [email protected] ... The gate metal-lization directly follows the gate recess using the same mask, allowing simple device scaling, required for high ...
The potentialities of AlGaN/GaN nanochannels with broken symmetry (also called self-switching dio... more The potentialities of AlGaN/GaN nanochannels with broken symmetry (also called self-switching diodes) as direct and heterodyne THz detectors are analyzed. The operation of the devices in the free space heterodyne detection scheme have been measured at room temperature with RF up to 0.32 THz and explained as a result of high-frequency nonlinearities using Monte Carlo simulations. Intermediate-frequency bandwidth of 40 GHz is obtained.
International Electron Devices Meeting 2000. Technical Digest. IEDM (Cat. No.00CH37138)
In this work we present results related to the currentholtage characteristics collapse in GaN MES... more In this work we present results related to the currentholtage characteristics collapse in GaN MESFETs. Two different failure mechanisms were observed, one of them clearly consists in a positive threshold voltage shift. Traps responsible for the "current collapse" were also characterized by means of different measurement techniques. Phototransient experiments show the presence of a capture barrier of O.leV while by a spectroscopic technique four photoionization energy levels were estimated. Finally, electroluminescence measurements shows the presence of visible and UV light, suggesting the presence of a self-recovery mechanisms.
In AlGaN/GaN heterostructure field-effect transistors (HEMTs) structures, the surface defects and... more In AlGaN/GaN heterostructure field-effect transistors (HEMTs) structures, the surface defects and dislocations may serve as trapping centers and affect the device performance via leakage current and lowfrequency noise. This work demonstrates the effect of surface passivation on the current-voltage characteristics and we report results of our investigation of the trapping characteristics of Si 3 N 4 -passivated AlGaN/GaN HEMTs on SiC substrates using the conductance deep levels transient spectroscopy (CDLTS) technique. From the measured of CDLTS we identified one electron trap had an activation energy of 0.31 eV it has been located in the AlGaN layer and two hole-likes traps H 1 , H 2 . It has been pointed out that the two hole-likes traps signals did not originate from changes in hole trap population in the channel, but reflected the changes in the electron population in the surface states of the HEMT access regions.
... or a setreset (SR) latch [10]. Similarly GaAs-based three-terminal nanowire junctions contro... more ... or a setreset (SR) latch [10]. Similarly GaAs-based three-terminal nanowire junctions controlled by Schottky wrap gates (WPGs) [11] are known to operate as Boolean gates [12]. Also recently, power gain at room temperature ...
The effects of the gate recess topologies on the linearity performance of PHEMT's have been ... more The effects of the gate recess topologies on the linearity performance of PHEMT's have been investigated in the Ka band. The authors highlight the reasons why, at a given output power level, the double recessed device exhibits a very large improvement of its intermodulation performance as its drain source bias voltage is increased whereas its linearity is inferior to that of the single recessed device at low drain source bias voltage. The effect of the load impedance on the linearity behavior has also been investigated. At a given output power the load impedance contour of the double recess structure is shown to exhibit a much larger variation of the intermodulation ratio than that of the single recess structure
ABSTRACT In this letter, we report load pull measurements on SiGe HBTs at 94 GHz. Nowadays, this ... more ABSTRACT In this letter, we report load pull measurements on SiGe HBTs at 94 GHz. Nowadays, this kind of device exhibits $F_{\rm MAX}$ above 400 GHz and thus has a growing interest for W-band applications. A load pull test bench is developed for the characterization of this device with special care on architecture and calibration procedure for accurate measurements in 75–110 GHz. The device was characterized under large signal operation showing attractive performance for power amplifier design. A state-of-the-art power density of 18.5 $\hbox{mW}/\mu\hbox{m}^{2}$ at 1-dB compression has been obtained at 94 GHz.
ABSTRACT The first results obtained from AlGaN/GaN HEMT devices on MBE epitaxial structures grown... more ABSTRACT The first results obtained from AlGaN/GaN HEMT devices on MBE epitaxial structures grown on 'composite' substrates are presented. These substrates are based on innovative structures in which a thin Si single crystal layer is transferred on top of a thick polycrystalline SiC wafer. The fabrication of the transistors is based on a process flow close to those used on epitaxy on Si bulk substrates. The results show the capabilities of such composite devices, providing HEMT devices for microwave power applications.
In this work the technology and characterization of nanocrystalline diamond (NCD) films directly ... more In this work the technology and characterization of nanocrystalline diamond (NCD) films directly grown on InAlN/GaN HEMTs is presented. Optimization of GaN based HEMT process steps including metallization stacks is discussed. A fully processed InAlN/GaN HEMT structure with 7 nm barrier has been overgrown in a temperature range of 750°C to 800°C with a 500 nm thick nanocrystalline diamond film in a Hot Filament CVD system. First results of semi-enhancement mode of DC and RF HEMT operation are reported. The grown NCD films were characterized by SEM, TEM, and Raman spectroscopy. Although no direct thermal conductivity measurements are conducted yet; the performed experiments shows the compatibility of growing high quality NCD films, several microns thick, on InAlN/GaN HEMTs as a potential material for heat extraction purposes.
a b s t r a c t Design optimization of the InAs self-switching diode (SSD) intended for direct ze... more a b s t r a c t Design optimization of the InAs self-switching diode (SSD) intended for direct zero-bias THz detection is presented. The SSD, which consists of nanometer-sized channels in parallel, was described using an equivalent small-signal circuit. Expressions for voltage responsivity and noise equivalent power (NEP) were derived in terms of geometrical design parameters of the SSD, i.e. the channel length and the number of channels. Modeled design dependencies were confirmed by RF and DC measurements on InAs SSDs. In terms of NEP, an optimum number of channels were found with the detector driven by a 50 X source. With a matched source, the model predicted a responsivity of 1900 V/W and NEP of 7.7 pW/Hz ½ for a single-channel InAs SSD with 35 nm channel width. Monte Carlo device simulations supported observed design dependencies. The proposed small-signal model can be used to optimize SSDs of any material system for low-noise and high-frequency operation as zero-bias detectors. In large signal measurements, the responsivity of the InAs SSDs exhibited a 1 dB deviation from linear responsivity at an input power of À3 dBm from a 50 X source.
A self-switching diode (SSD) is based on an asymmetric nanochannel. The SSD is fabricated by tail... more A self-switching diode (SSD) is based on an asymmetric nanochannel. The SSD is fabricated by tailoring the boundary of a narrow semiconductor channel to break its symmetry. An applied voltage V not only changes the potential profile along the channel direction but also either widens or narrows the effective channel width, depending on its sign. This results in a strong nonlinear current-voltage I-V characteristic, resembling that of a conventional diode which could be used for detection. Besides, the special geometry of SSDs benefits the onset of Gunn oscillations since the electrical field is well focused at the cathode side of the channel and the electron concentration is increased by the side field effect, so that the classical criteria for Gunn oscillations are more easily reached. The main advantage of using GaN is that it will provide much higher power than traditional GaAs Gunn diodes at very high frequency (in excess of 300 GHz) due to its high saturation velocity, high breakdown field and the possibility of high temperature operation. Here, detection measurements will be presented.
The high potential at microwave frequencies of AlGaN/GaN HEMTs on sapphire substrate for power ap... more The high potential at microwave frequencies of AlGaN/GaN HEMTs on sapphire substrate for power application has been demonstrated in this paper. An output power density close to 5W/mm has been measured on a 2x25x0.5µm² HEMT on sapphire substrate. This result is very interesting because the devices have not been passivated. At present time, it is the best power result in
AlGaN/GaN high electron mobility transistors (HEMTs) with Si and Al 2 O 3 substrates reveals anom... more AlGaN/GaN high electron mobility transistors (HEMTs) with Si and Al 2 O 3 substrates reveals anomalies on I ds -V ds -T and I gs -V gs -T characteristics (degradation in drain current, kink effect, barrier height fluctuations, etc.). Stress and random telegraph signal (RTS) measurements prove the presence of trap centers responsible for drain current degradation. An explanation of the trapping mechanism responsible for current instabilities is proposed. Deep defects analysis performed by capacitance transient spectroscopy (C-DLTS), frequency dispersion of the output conductance (G ds (f)), respectively, on gate/source and drain/source contacts and RTS prove the presence of deep defects localized, respectively, in the gate and in the channel regions. Defects detected by C-DLTS and G ds (f) are strongly correlated, respectively, to barrier height inhomogeneities and kink anomalies. Gate current analysis confirms the presence of (G-R) centers acting like traps at the interface GaN/AlGaN. Finally, the localization of these traps defects is proposed. q
International Conference on Molecular Bean Epitaxy, 2002
In this paper, we report on the properties of GaN films and AlGaN/GaN HEMT structures grown by mo... more In this paper, we report on the properties of GaN films and AlGaN/GaN HEMT structures grown by molecular beam epitaxy on resistive Si(1 1 1) substrates. The properties of the GaN buffer layer and the AlGaN/GaN HEMTs are presented. Finally, both static and high-frequency performances of sub-micron gate length devices are analyzed demonstrating their RF power capability. r 2002 Elsevier Science B.V. All rights reserved. PACS: 73.40.kp; 81.15.Hi; 85.30.Tv Keywords: A3. Molecular beam epitaxy; B2. GaN; B3. High electron mobility transistors 0022-0248/03/$ -see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 -0 2 4 8 ( 0 2 ) 0 2 1 4 9 -8
ABSTRACT We investigated a 2 nm thin InAlN/AlN barrier after recessing of a GaN cap on top of it ... more ABSTRACT We investigated a 2 nm thin InAlN/AlN barrier after recessing of a GaN cap on top of it and Ir gate metallization. Detailed analysis of the recess process revealed practically no damage until the formation of an etch-resistant barrier layer producing nitrogen vacancies and hence defect assisted tunneling through the thin barrier. Annealing of the Ir-based gate stack showed a reduction of the electrical distance between the gate and the channel. The effect was linked to an oxygen-containing interface layer between the Ir metal and the InAlN layer where oxygen diffused into Ir at elevated temperatures. Resulting devices showed state-of-the-art normally-off performance.
High-temperature effects on the electrical behavior of AlGaN/GaN HEMTs have been evaluated. dc me... more High-temperature effects on the electrical behavior of AlGaN/GaN HEMTs have been evaluated. dc measurements have been performed for different illumination and temperature conditions. The unpassivated devices present a good ohmic contact technology up to 550°C in air. These high-temperature electrical measurements have also shown the existence of electrical traps. These traps are sensitive to the bias point, the illumination, and the temperature.
2016 11th European Microwave Integrated Circuits Conference (EuMIC), 2016
In this paper, we report anomaly and intrinsic capacitance behaviour over temperature of AlGaN/Ga... more In this paper, we report anomaly and intrinsic capacitance behaviour over temperature of AlGaN/GaN/SiC and AlGaAs/GaAs high electron mobility transistors using on wafer measurement up to 50 GHz. Differences are observed; most notably that the trend of the intrinsic capacitances behaviour with temperature of the two device technologies are completely different. This anomaly continues for the other device parameter such as threshold voltage, two-dimension electro gas sheet carrier densities as well. These results are valuable for the future design optimizations of the advanced GaN and GaAs based monolithic microwave integrated circuit operating at high frequency and temperature.
... W. Schrenk, G. Strasser, and D. Pogany are with the Vienna University of Technology, 1040 Vie... more ... W. Schrenk, G. Strasser, and D. Pogany are with the Vienna University of Technology, 1040 Vienna, Austria (e-mail: [email protected] ... The gate metal-lization directly follows the gate recess using the same mask, allowing simple device scaling, required for high ...
The potentialities of AlGaN/GaN nanochannels with broken symmetry (also called self-switching dio... more The potentialities of AlGaN/GaN nanochannels with broken symmetry (also called self-switching diodes) as direct and heterodyne THz detectors are analyzed. The operation of the devices in the free space heterodyne detection scheme have been measured at room temperature with RF up to 0.32 THz and explained as a result of high-frequency nonlinearities using Monte Carlo simulations. Intermediate-frequency bandwidth of 40 GHz is obtained.
International Electron Devices Meeting 2000. Technical Digest. IEDM (Cat. No.00CH37138)
In this work we present results related to the currentholtage characteristics collapse in GaN MES... more In this work we present results related to the currentholtage characteristics collapse in GaN MESFETs. Two different failure mechanisms were observed, one of them clearly consists in a positive threshold voltage shift. Traps responsible for the "current collapse" were also characterized by means of different measurement techniques. Phototransient experiments show the presence of a capture barrier of O.leV while by a spectroscopic technique four photoionization energy levels were estimated. Finally, electroluminescence measurements shows the presence of visible and UV light, suggesting the presence of a self-recovery mechanisms.
In AlGaN/GaN heterostructure field-effect transistors (HEMTs) structures, the surface defects and... more In AlGaN/GaN heterostructure field-effect transistors (HEMTs) structures, the surface defects and dislocations may serve as trapping centers and affect the device performance via leakage current and lowfrequency noise. This work demonstrates the effect of surface passivation on the current-voltage characteristics and we report results of our investigation of the trapping characteristics of Si 3 N 4 -passivated AlGaN/GaN HEMTs on SiC substrates using the conductance deep levels transient spectroscopy (CDLTS) technique. From the measured of CDLTS we identified one electron trap had an activation energy of 0.31 eV it has been located in the AlGaN layer and two hole-likes traps H 1 , H 2 . It has been pointed out that the two hole-likes traps signals did not originate from changes in hole trap population in the channel, but reflected the changes in the electron population in the surface states of the HEMT access regions.
... or a setreset (SR) latch [10]. Similarly GaAs-based three-terminal nanowire junctions contro... more ... or a setreset (SR) latch [10]. Similarly GaAs-based three-terminal nanowire junctions controlled by Schottky wrap gates (WPGs) [11] are known to operate as Boolean gates [12]. Also recently, power gain at room temperature ...
The effects of the gate recess topologies on the linearity performance of PHEMT's have been ... more The effects of the gate recess topologies on the linearity performance of PHEMT's have been investigated in the Ka band. The authors highlight the reasons why, at a given output power level, the double recessed device exhibits a very large improvement of its intermodulation performance as its drain source bias voltage is increased whereas its linearity is inferior to that of the single recessed device at low drain source bias voltage. The effect of the load impedance on the linearity behavior has also been investigated. At a given output power the load impedance contour of the double recess structure is shown to exhibit a much larger variation of the intermodulation ratio than that of the single recess structure
ABSTRACT In this letter, we report load pull measurements on SiGe HBTs at 94 GHz. Nowadays, this ... more ABSTRACT In this letter, we report load pull measurements on SiGe HBTs at 94 GHz. Nowadays, this kind of device exhibits $F_{\rm MAX}$ above 400 GHz and thus has a growing interest for W-band applications. A load pull test bench is developed for the characterization of this device with special care on architecture and calibration procedure for accurate measurements in 75–110 GHz. The device was characterized under large signal operation showing attractive performance for power amplifier design. A state-of-the-art power density of 18.5 $\hbox{mW}/\mu\hbox{m}^{2}$ at 1-dB compression has been obtained at 94 GHz.
ABSTRACT The first results obtained from AlGaN/GaN HEMT devices on MBE epitaxial structures grown... more ABSTRACT The first results obtained from AlGaN/GaN HEMT devices on MBE epitaxial structures grown on 'composite' substrates are presented. These substrates are based on innovative structures in which a thin Si single crystal layer is transferred on top of a thick polycrystalline SiC wafer. The fabrication of the transistors is based on a process flow close to those used on epitaxy on Si bulk substrates. The results show the capabilities of such composite devices, providing HEMT devices for microwave power applications.
In this work the technology and characterization of nanocrystalline diamond (NCD) films directly ... more In this work the technology and characterization of nanocrystalline diamond (NCD) films directly grown on InAlN/GaN HEMTs is presented. Optimization of GaN based HEMT process steps including metallization stacks is discussed. A fully processed InAlN/GaN HEMT structure with 7 nm barrier has been overgrown in a temperature range of 750°C to 800°C with a 500 nm thick nanocrystalline diamond film in a Hot Filament CVD system. First results of semi-enhancement mode of DC and RF HEMT operation are reported. The grown NCD films were characterized by SEM, TEM, and Raman spectroscopy. Although no direct thermal conductivity measurements are conducted yet; the performed experiments shows the compatibility of growing high quality NCD films, several microns thick, on InAlN/GaN HEMTs as a potential material for heat extraction purposes.
a b s t r a c t Design optimization of the InAs self-switching diode (SSD) intended for direct ze... more a b s t r a c t Design optimization of the InAs self-switching diode (SSD) intended for direct zero-bias THz detection is presented. The SSD, which consists of nanometer-sized channels in parallel, was described using an equivalent small-signal circuit. Expressions for voltage responsivity and noise equivalent power (NEP) were derived in terms of geometrical design parameters of the SSD, i.e. the channel length and the number of channels. Modeled design dependencies were confirmed by RF and DC measurements on InAs SSDs. In terms of NEP, an optimum number of channels were found with the detector driven by a 50 X source. With a matched source, the model predicted a responsivity of 1900 V/W and NEP of 7.7 pW/Hz ½ for a single-channel InAs SSD with 35 nm channel width. Monte Carlo device simulations supported observed design dependencies. The proposed small-signal model can be used to optimize SSDs of any material system for low-noise and high-frequency operation as zero-bias detectors. In large signal measurements, the responsivity of the InAs SSDs exhibited a 1 dB deviation from linear responsivity at an input power of À3 dBm from a 50 X source.
A self-switching diode (SSD) is based on an asymmetric nanochannel. The SSD is fabricated by tail... more A self-switching diode (SSD) is based on an asymmetric nanochannel. The SSD is fabricated by tailoring the boundary of a narrow semiconductor channel to break its symmetry. An applied voltage V not only changes the potential profile along the channel direction but also either widens or narrows the effective channel width, depending on its sign. This results in a strong nonlinear current-voltage I-V characteristic, resembling that of a conventional diode which could be used for detection. Besides, the special geometry of SSDs benefits the onset of Gunn oscillations since the electrical field is well focused at the cathode side of the channel and the electron concentration is increased by the side field effect, so that the classical criteria for Gunn oscillations are more easily reached. The main advantage of using GaN is that it will provide much higher power than traditional GaAs Gunn diodes at very high frequency (in excess of 300 GHz) due to its high saturation velocity, high breakdown field and the possibility of high temperature operation. Here, detection measurements will be presented.
The high potential at microwave frequencies of AlGaN/GaN HEMTs on sapphire substrate for power ap... more The high potential at microwave frequencies of AlGaN/GaN HEMTs on sapphire substrate for power application has been demonstrated in this paper. An output power density close to 5W/mm has been measured on a 2x25x0.5µm² HEMT on sapphire substrate. This result is very interesting because the devices have not been passivated. At present time, it is the best power result in
AlGaN/GaN high electron mobility transistors (HEMTs) with Si and Al 2 O 3 substrates reveals anom... more AlGaN/GaN high electron mobility transistors (HEMTs) with Si and Al 2 O 3 substrates reveals anomalies on I ds -V ds -T and I gs -V gs -T characteristics (degradation in drain current, kink effect, barrier height fluctuations, etc.). Stress and random telegraph signal (RTS) measurements prove the presence of trap centers responsible for drain current degradation. An explanation of the trapping mechanism responsible for current instabilities is proposed. Deep defects analysis performed by capacitance transient spectroscopy (C-DLTS), frequency dispersion of the output conductance (G ds (f)), respectively, on gate/source and drain/source contacts and RTS prove the presence of deep defects localized, respectively, in the gate and in the channel regions. Defects detected by C-DLTS and G ds (f) are strongly correlated, respectively, to barrier height inhomogeneities and kink anomalies. Gate current analysis confirms the presence of (G-R) centers acting like traps at the interface GaN/AlGaN. Finally, the localization of these traps defects is proposed. q
International Conference on Molecular Bean Epitaxy, 2002
In this paper, we report on the properties of GaN films and AlGaN/GaN HEMT structures grown by mo... more In this paper, we report on the properties of GaN films and AlGaN/GaN HEMT structures grown by molecular beam epitaxy on resistive Si(1 1 1) substrates. The properties of the GaN buffer layer and the AlGaN/GaN HEMTs are presented. Finally, both static and high-frequency performances of sub-micron gate length devices are analyzed demonstrating their RF power capability. r 2002 Elsevier Science B.V. All rights reserved. PACS: 73.40.kp; 81.15.Hi; 85.30.Tv Keywords: A3. Molecular beam epitaxy; B2. GaN; B3. High electron mobility transistors 0022-0248/03/$ -see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 -0 2 4 8 ( 0 2 ) 0 2 1 4 9 -8
ABSTRACT We investigated a 2 nm thin InAlN/AlN barrier after recessing of a GaN cap on top of it ... more ABSTRACT We investigated a 2 nm thin InAlN/AlN barrier after recessing of a GaN cap on top of it and Ir gate metallization. Detailed analysis of the recess process revealed practically no damage until the formation of an etch-resistant barrier layer producing nitrogen vacancies and hence defect assisted tunneling through the thin barrier. Annealing of the Ir-based gate stack showed a reduction of the electrical distance between the gate and the channel. The effect was linked to an oxygen-containing interface layer between the Ir metal and the InAlN layer where oxygen diffused into Ir at elevated temperatures. Resulting devices showed state-of-the-art normally-off performance.
High-temperature effects on the electrical behavior of AlGaN/GaN HEMTs have been evaluated. dc me... more High-temperature effects on the electrical behavior of AlGaN/GaN HEMTs have been evaluated. dc measurements have been performed for different illumination and temperature conditions. The unpassivated devices present a good ohmic contact technology up to 550°C in air. These high-temperature electrical measurements have also shown the existence of electrical traps. These traps are sensitive to the bias point, the illumination, and the temperature.
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Papers by C. Gaquiere