This paper describes how duty cycling can reduce the power consumption of an On Off Keying (OOK),... more This paper describes how duty cycling can reduce the power consumption of an On Off Keying (OOK), 2.4 GHz, super regenerative transceiver from 400 mu W for the transmit (Tx) to 30 mu W and from 380 mu W for the receive (Rx) to 10 mu W. This is a power reduction of 92.5% for the Tx and 97.4% for the Rx. Despite the low power consumption exhibited by the Tx an effective output power of -11 dBm is achieved. This is due to the fact that the Tx oscillator is turned on for a very short period of time compared to the bit period. The output of the Rx is then lengthened digitally to reproduce the correct duty cycle. The duty cycled Rx achieves an output voltage of 1mV for an input power of -50 dBm. Also presented is a high impedance receiver which produces an output of 5 mV for an input power of -90 dBm.
This paper reports a novel method for producing low ohmic contact resistance, RC, as well as low ... more This paper reports a novel method for producing low ohmic contact resistance, RC, as well as low sheet resistance, Rsh, on AlN/GaN MOS-HEMT structures. The method relies on the protection of the very sensitive AlN epi-layer from exposure to liquid chemicals during processing using evaporated Al, which on thermal oxidation forms Al2O3. The Al2O3 acts as a surface passivant and
This paper reports on the processing and characterization of AlN/GaN metal-oxide-semiconductor hi... more This paper reports on the processing and characterization of AlN/GaN metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs). The devices employ thermally grown Al 2 O 3 as a gate dielectric and surface protection and passivation, which is an approach that provides an opportunity to define the ohmic contact areas by wet etching of Al (and optimization of this processing step) prior to the formation of Al 2 O 3 and ohmic metal deposition. The devices also employ a new process technique that significantly suppresses leakage currents on the mesa sidewalls. Fabricated devices exhibited good direct current and radio frequency performance. A high peak current, i.e., ∼1.5 A/mm, at V GS = +3 V and a current-gain cutoff frequency f T and maximum oscillation frequency f MAX of 50 and 40 GHz, respectively, were obtained for a device with 0.2-μm gate length and 100-μm gate width. Additionally, a robust method for the extraction of the small-signal equivalent circuit suitable for process optimization is described. It relies on intimate process knowledge and device geometry to determine equivalent circuit elements of the fabricated AlN/GaN MOS-HEMTs. Index Terms-AlGaN/GaN, AlN/GaN, Al 2 O 3 , equivalent circuit, high-electron mobility transistor (HEMT), metal-oxidesemiconductor (MOS)-HEMT, small-signal model, thermal oxidation, wet etching. I. INTRODUCTION T O DATE, GaN-based high-electron mobility transistors (HEMTs), particularly AlGaN/GaN devices have demonstrated state-of-the-art performance in terms of power density and cutoff frequency [1], [2]. With the impressive achievements on the device level, high-power amplifier monolithic microwave integrated circuits up to Ka-band have been also realized [3], [4]. Today, the demand for higher power devices at higher frequencies is very strong. Therefore, the performance of GaNbased HEMTs is being pushed to achieve maximum power and speed levels possible. In order to increase further the twodimensional electron gas (2-DEG) density and the breakdown field in the AlGaN/GaN structure, high Al mole fraction is desirable to increase the strength of polarization. However, from a growth perspective, it is difficult to grow high-quality Al x Ga 1−x N layers with high-Al content, which results in poor transport properties of Al x Ga 1−x N/GaN structures with x >
We investigate the effect of increasing of GaN cap thickness on I-V characteristics of the 1 µm g... more We investigate the effect of increasing of GaN cap thickness on I-V characteristics of the 1 µm gate length GaN/AlGaN/AlN/GaN HEMT. This device is passivated with 10nm SiN, has a n-type uniformly doped 2 nm-thick GaN cap, 20 nm AlGaN barrier layer, 1nm AlN spacer layer above the channel, and 3 µm GaN buffer. Figure 1 shows a cross-section of the GaN/AlGaN/AlN/GaN HEMT with a 10 nm SiN passivation layer which we have used as a starting point in our study. The device ID-VG characteristics have been calibrated using Silvaco ATLAS commercial device modelling tool by S. Faramehr et al. [1]. For simplicity, in our investigation, we have reduced the thickness of SiN passivation layer to 2 nm. However, such thin passivation layer is not always used [2]. In order to calibrate device ID-VG characteristics to experimental data, we have assumed interface traps with a density of 9×〖10〗^12 〖cm〗^(-2) located on the surface of GaN cap layer. All the modelling were done at a low and high drain volta...
The demand for higher frequency applications is growing and a solid-state source for THz frequenc... more The demand for higher frequency applications is growing and a solid-state source for THz frequencies is needed. We compare experimetally demosntarted results of resonant tunnleing diode and planar Gunn diodes for terahertz technology. The highest power demonstrated for W-band RTD oscillators at 75.2 GHz with-0.2 dBm (0.96 mW) and at 300GHz for submicron planar Gunn with-16dBm (28µW) are compared as the potential solid-state source for Terahertz applications.
Spike-based neuromorphic devices promise to alleviate the energy greed of the artificial intellig... more Spike-based neuromorphic devices promise to alleviate the energy greed of the artificial intelligence hardware by using spiking neural networks (SNNs), which employ neuron like units to process information through the timing of the spikes. These neuron-like devices only consume energy when active. Recent works have shown that resonant tunnelling diodes (RTDs) incorporating optoelectronic functionalities such as photodetection and light emission can play a major role on photonic SNNs. RTDs are devices that display an N-shaped current-voltage characteristics capable of providing negative differential conductance (NDC) over a range of the operating voltages. Specifically, RTD photodetectors (RTD-PDs) show promise due to their unique mixture of the structural simplicity while simultaneously providing highly complex non-linear behavior. The goal of this work is to present a systematic study of the how the thickness of the RTD-PD light absorption layers (100, 250, 500 nm) and the device s...
The thickness increase of gallium nitride (GaN) cap layer from 2 nm to 35 nm to achieve an enhanc... more The thickness increase of gallium nitride (GaN) cap layer from 2 nm to 35 nm to achieve an enhancement mode GaN MIS-HEMT (Metal-Insulator-Semiconductor High-Electron-Mobility Transistor) with a threshold voltage (V th) of +0.5 V is studied using TCAD simulations. The simulations are calibrated to measured I-V characteristics of the 1 µm gate length GaN MIS-HEMT with the 2 nm thick GaN cap. A good agreement at low and high drain voltages (V DS =1 V and 5 V) between simulations and measurements is achieved by using a quantum-corrected drift-diffusion transport model. The enhancement mode GaN MIS-HEMT with a GaN cap thickness of 35 nm achieves V th = +0.5 V thanks to positive interface traps occurring between the SiN passivation layer and the GaN cap as reported experimentally. The simulations indicate that a parasitic channel is created at the interface between the SiN layer and the 35 nm GaN cap. Our study also shows an increase in the breakdown voltage from 100 V to 870 V when a thickness of the GaN cap layer increases from 15 nm to 35 nm.
This paper describes a 380uW Rx, 56uW Tx, 2.4 GHz, GaAs based, super- regenerative transceiver. D... more This paper describes a 380uW Rx, 56uW Tx, 2.4 GHz, GaAs based, super- regenerative transceiver. Despite the ultra low power consumption exhibited by the Tx, an output power of -11 dBm is achieved. This is due to the fact that the oscillator is only on for a very short period of time compared to the bit period. The received signal at the RF output is amplified, bit sliced and then lengthened digitally to reproduce the correct duty cycle.
CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009
The development of optoelectronic integrated circuits (OEIC) that combine optical and electronic ... more The development of optoelectronic integrated circuits (OEIC) that combine optical and electronic functionalities on a single chip have been driven by numerous telecommunications applications including microwave-optical interfaces for radio-over-fiber picocellular networks for the next-generation wireless communication systems, also know as fourth-generation (4G) systems. The integration of a resonant tunnelling diode (RTD) with laser diode (LD) gives rise to a novel nonlinear optoelectronic oscillator, the RTD- LD oscillator, with innovative functionalities capable of various electro-photonic operation modes including optoelectronic voltage controlled oscillator and synchronization to low power RF signals. The circuit nonlinear behaviour is a consequence of the RTD nonlinear current-voltage characteristic that shows negative differential resistance region. This paper investigates by experimental evidence the potential application of the RTD-LD oscillator as a wireless-to- optical (WO) converter. The RTD-LD WO converter includes a patch antenna for directional reception of broadcasted signals at microwave frequencies. In the presence of radio-broadcasted signals with frequencies within the RTD-LD oscillator locking ranges the radio sub-carrier of the laser optical output follows the phase of the broadcasted signals with significant noise reduction around the locking frequencies. The circuit locking ranges around the oscillator's natural frequency and its sub-harmonics/harmonics frequencies are controlled by the oscillator quiescent bias voltage.
Proceedings of SPIE - The International Society for Optical Engineering, 2009
Recent work on an OptoElectronic Integrated Circuit (OEIC), the resonant tunneling diode-laser di... more Recent work on an OptoElectronic Integrated Circuit (OEIC), the resonant tunneling diode-laser diode (RTD-LD) has shown that it can act as an optoelectronic voltage controlled oscillator (OVCO). The RTD-LD oscillates because of the negative differential resistance of the RTD and simply providing the RTD-LD with a dc voltage will cause it to oscillate at frequencies determined by both the external
The authors report on a hybrid integration of a resonant tunnelling diode laser diode driver conf... more The authors report on a hybrid integration of a resonant tunnelling diode laser diode driver configuration that can operate as a self-oscillating circuit, and when externally perturbed shows regions of frequency division and frequency multiplication, quasi-periodic and chaotic oscillations, both in the optical and electrical outputs. The authors also demonstrate that this optoelectronic circuit is well described as a Liénard's oscillator. The synchronisation capabilities of the circuit have potentially novel functions for optical communications systems including clock recovery, clock division and data encryption.
IEEE Transactions on Microwave Theory and Techniques, 2002
Direct extraction is the most accurate method for the determination of equivalent-circuits of het... more Direct extraction is the most accurate method for the determination of equivalent-circuits of heterojunction bipolar transistors (HBTs). The method is based on first determining the parasitic elements and then the intrinsic elements analytically. The accuracy and robustness of the whole algorithm therefore is determined by the quality of the extraction of the extrinsic elements. This paper focuses on a new
AbstractWe report on experimental and modeling results on the nonlinear dynamics of a resonant-t... more AbstractWe report on experimental and modeling results on the nonlinear dynamics of a resonant-tunneling-diode-based (RTD) optoelectronic circuits that can be used as the basis of a wireless/optical interface for wireless access networks. The RTD-based circuits are ...
This paper describes how duty cycling can reduce the power consumption of an On Off Keying (OOK),... more This paper describes how duty cycling can reduce the power consumption of an On Off Keying (OOK), 2.4 GHz, super regenerative transceiver from 400 mu W for the transmit (Tx) to 30 mu W and from 380 mu W for the receive (Rx) to 10 mu W. This is a power reduction of 92.5% for the Tx and 97.4% for the Rx. Despite the low power consumption exhibited by the Tx an effective output power of -11 dBm is achieved. This is due to the fact that the Tx oscillator is turned on for a very short period of time compared to the bit period. The output of the Rx is then lengthened digitally to reproduce the correct duty cycle. The duty cycled Rx achieves an output voltage of 1mV for an input power of -50 dBm. Also presented is a high impedance receiver which produces an output of 5 mV for an input power of -90 dBm.
This paper reports a novel method for producing low ohmic contact resistance, RC, as well as low ... more This paper reports a novel method for producing low ohmic contact resistance, RC, as well as low sheet resistance, Rsh, on AlN/GaN MOS-HEMT structures. The method relies on the protection of the very sensitive AlN epi-layer from exposure to liquid chemicals during processing using evaporated Al, which on thermal oxidation forms Al2O3. The Al2O3 acts as a surface passivant and
This paper reports on the processing and characterization of AlN/GaN metal-oxide-semiconductor hi... more This paper reports on the processing and characterization of AlN/GaN metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs). The devices employ thermally grown Al 2 O 3 as a gate dielectric and surface protection and passivation, which is an approach that provides an opportunity to define the ohmic contact areas by wet etching of Al (and optimization of this processing step) prior to the formation of Al 2 O 3 and ohmic metal deposition. The devices also employ a new process technique that significantly suppresses leakage currents on the mesa sidewalls. Fabricated devices exhibited good direct current and radio frequency performance. A high peak current, i.e., ∼1.5 A/mm, at V GS = +3 V and a current-gain cutoff frequency f T and maximum oscillation frequency f MAX of 50 and 40 GHz, respectively, were obtained for a device with 0.2-μm gate length and 100-μm gate width. Additionally, a robust method for the extraction of the small-signal equivalent circuit suitable for process optimization is described. It relies on intimate process knowledge and device geometry to determine equivalent circuit elements of the fabricated AlN/GaN MOS-HEMTs. Index Terms-AlGaN/GaN, AlN/GaN, Al 2 O 3 , equivalent circuit, high-electron mobility transistor (HEMT), metal-oxidesemiconductor (MOS)-HEMT, small-signal model, thermal oxidation, wet etching. I. INTRODUCTION T O DATE, GaN-based high-electron mobility transistors (HEMTs), particularly AlGaN/GaN devices have demonstrated state-of-the-art performance in terms of power density and cutoff frequency [1], [2]. With the impressive achievements on the device level, high-power amplifier monolithic microwave integrated circuits up to Ka-band have been also realized [3], [4]. Today, the demand for higher power devices at higher frequencies is very strong. Therefore, the performance of GaNbased HEMTs is being pushed to achieve maximum power and speed levels possible. In order to increase further the twodimensional electron gas (2-DEG) density and the breakdown field in the AlGaN/GaN structure, high Al mole fraction is desirable to increase the strength of polarization. However, from a growth perspective, it is difficult to grow high-quality Al x Ga 1−x N layers with high-Al content, which results in poor transport properties of Al x Ga 1−x N/GaN structures with x >
We investigate the effect of increasing of GaN cap thickness on I-V characteristics of the 1 µm g... more We investigate the effect of increasing of GaN cap thickness on I-V characteristics of the 1 µm gate length GaN/AlGaN/AlN/GaN HEMT. This device is passivated with 10nm SiN, has a n-type uniformly doped 2 nm-thick GaN cap, 20 nm AlGaN barrier layer, 1nm AlN spacer layer above the channel, and 3 µm GaN buffer. Figure 1 shows a cross-section of the GaN/AlGaN/AlN/GaN HEMT with a 10 nm SiN passivation layer which we have used as a starting point in our study. The device ID-VG characteristics have been calibrated using Silvaco ATLAS commercial device modelling tool by S. Faramehr et al. [1]. For simplicity, in our investigation, we have reduced the thickness of SiN passivation layer to 2 nm. However, such thin passivation layer is not always used [2]. In order to calibrate device ID-VG characteristics to experimental data, we have assumed interface traps with a density of 9×〖10〗^12 〖cm〗^(-2) located on the surface of GaN cap layer. All the modelling were done at a low and high drain volta...
The demand for higher frequency applications is growing and a solid-state source for THz frequenc... more The demand for higher frequency applications is growing and a solid-state source for THz frequencies is needed. We compare experimetally demosntarted results of resonant tunnleing diode and planar Gunn diodes for terahertz technology. The highest power demonstrated for W-band RTD oscillators at 75.2 GHz with-0.2 dBm (0.96 mW) and at 300GHz for submicron planar Gunn with-16dBm (28µW) are compared as the potential solid-state source for Terahertz applications.
Spike-based neuromorphic devices promise to alleviate the energy greed of the artificial intellig... more Spike-based neuromorphic devices promise to alleviate the energy greed of the artificial intelligence hardware by using spiking neural networks (SNNs), which employ neuron like units to process information through the timing of the spikes. These neuron-like devices only consume energy when active. Recent works have shown that resonant tunnelling diodes (RTDs) incorporating optoelectronic functionalities such as photodetection and light emission can play a major role on photonic SNNs. RTDs are devices that display an N-shaped current-voltage characteristics capable of providing negative differential conductance (NDC) over a range of the operating voltages. Specifically, RTD photodetectors (RTD-PDs) show promise due to their unique mixture of the structural simplicity while simultaneously providing highly complex non-linear behavior. The goal of this work is to present a systematic study of the how the thickness of the RTD-PD light absorption layers (100, 250, 500 nm) and the device s...
The thickness increase of gallium nitride (GaN) cap layer from 2 nm to 35 nm to achieve an enhanc... more The thickness increase of gallium nitride (GaN) cap layer from 2 nm to 35 nm to achieve an enhancement mode GaN MIS-HEMT (Metal-Insulator-Semiconductor High-Electron-Mobility Transistor) with a threshold voltage (V th) of +0.5 V is studied using TCAD simulations. The simulations are calibrated to measured I-V characteristics of the 1 µm gate length GaN MIS-HEMT with the 2 nm thick GaN cap. A good agreement at low and high drain voltages (V DS =1 V and 5 V) between simulations and measurements is achieved by using a quantum-corrected drift-diffusion transport model. The enhancement mode GaN MIS-HEMT with a GaN cap thickness of 35 nm achieves V th = +0.5 V thanks to positive interface traps occurring between the SiN passivation layer and the GaN cap as reported experimentally. The simulations indicate that a parasitic channel is created at the interface between the SiN layer and the 35 nm GaN cap. Our study also shows an increase in the breakdown voltage from 100 V to 870 V when a thickness of the GaN cap layer increases from 15 nm to 35 nm.
This paper describes a 380uW Rx, 56uW Tx, 2.4 GHz, GaAs based, super- regenerative transceiver. D... more This paper describes a 380uW Rx, 56uW Tx, 2.4 GHz, GaAs based, super- regenerative transceiver. Despite the ultra low power consumption exhibited by the Tx, an output power of -11 dBm is achieved. This is due to the fact that the oscillator is only on for a very short period of time compared to the bit period. The received signal at the RF output is amplified, bit sliced and then lengthened digitally to reproduce the correct duty cycle.
CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009
The development of optoelectronic integrated circuits (OEIC) that combine optical and electronic ... more The development of optoelectronic integrated circuits (OEIC) that combine optical and electronic functionalities on a single chip have been driven by numerous telecommunications applications including microwave-optical interfaces for radio-over-fiber picocellular networks for the next-generation wireless communication systems, also know as fourth-generation (4G) systems. The integration of a resonant tunnelling diode (RTD) with laser diode (LD) gives rise to a novel nonlinear optoelectronic oscillator, the RTD- LD oscillator, with innovative functionalities capable of various electro-photonic operation modes including optoelectronic voltage controlled oscillator and synchronization to low power RF signals. The circuit nonlinear behaviour is a consequence of the RTD nonlinear current-voltage characteristic that shows negative differential resistance region. This paper investigates by experimental evidence the potential application of the RTD-LD oscillator as a wireless-to- optical (WO) converter. The RTD-LD WO converter includes a patch antenna for directional reception of broadcasted signals at microwave frequencies. In the presence of radio-broadcasted signals with frequencies within the RTD-LD oscillator locking ranges the radio sub-carrier of the laser optical output follows the phase of the broadcasted signals with significant noise reduction around the locking frequencies. The circuit locking ranges around the oscillator's natural frequency and its sub-harmonics/harmonics frequencies are controlled by the oscillator quiescent bias voltage.
Proceedings of SPIE - The International Society for Optical Engineering, 2009
Recent work on an OptoElectronic Integrated Circuit (OEIC), the resonant tunneling diode-laser di... more Recent work on an OptoElectronic Integrated Circuit (OEIC), the resonant tunneling diode-laser diode (RTD-LD) has shown that it can act as an optoelectronic voltage controlled oscillator (OVCO). The RTD-LD oscillates because of the negative differential resistance of the RTD and simply providing the RTD-LD with a dc voltage will cause it to oscillate at frequencies determined by both the external
The authors report on a hybrid integration of a resonant tunnelling diode laser diode driver conf... more The authors report on a hybrid integration of a resonant tunnelling diode laser diode driver configuration that can operate as a self-oscillating circuit, and when externally perturbed shows regions of frequency division and frequency multiplication, quasi-periodic and chaotic oscillations, both in the optical and electrical outputs. The authors also demonstrate that this optoelectronic circuit is well described as a Liénard's oscillator. The synchronisation capabilities of the circuit have potentially novel functions for optical communications systems including clock recovery, clock division and data encryption.
IEEE Transactions on Microwave Theory and Techniques, 2002
Direct extraction is the most accurate method for the determination of equivalent-circuits of het... more Direct extraction is the most accurate method for the determination of equivalent-circuits of heterojunction bipolar transistors (HBTs). The method is based on first determining the parasitic elements and then the intrinsic elements analytically. The accuracy and robustness of the whole algorithm therefore is determined by the quality of the extraction of the extrinsic elements. This paper focuses on a new
AbstractWe report on experimental and modeling results on the nonlinear dynamics of a resonant-t... more AbstractWe report on experimental and modeling results on the nonlinear dynamics of a resonant-tunneling-diode-based (RTD) optoelectronic circuits that can be used as the basis of a wireless/optical interface for wireless access networks. The RTD-based circuits are ...
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Papers by E. Wasige