Malek Gassoumi - Academia.edu (original) (raw)

Papers by Malek Gassoumi

Journal of sol-gel science and technology, May 21, 2024

Journal of Ovonic Research

When the AlGaN/GaN high electron mobility transistor (HEMT) is strongly biased, the speed of the ... more When the AlGaN/GaN high electron mobility transistor (HEMT) is strongly biased, the speed of the electrons in the channel increases, which leads to an injection of electrons into the buffer, and consequently the appearance of the "short channel effect" phenomenon, which limits the performance of the component to overcome this effect and increase the power/frequency performance of the component, one solution consists in using a confinement barrier. This involves placing an electrostatic barrier under the GaN channel so as to block the injection of electrons into the buffer layer when the transistor is highly biased, and a BGaN confinement barrier because this semiconductor has very interesting physical properties, as well as better electrical isolation between the well and the substrate thanks to the optimization of the buffer. In this paper, the main objective is to study the effect of adding BGaN confinement barrier and its influence on transistor performance.

Journal of Ovonic Research

AlGaN/GaN/Si HEMTs have been investigated using current-voltage-temperature and CDLTS measurement... more AlGaN/GaN/Si HEMTs have been investigated using current-voltage-temperature and CDLTS measurements.As has been found from current voltage measurements, parasitic effects were revealed indicating the presence of traps in HEMT device. As a result, the origins of traps are determined from CDLTS experiments.

Ceramics International, 2002

Nanoscaled so called indium tin oxide In 2 O 3 :Sn (ITO) with a specific BET surface area of 50 m... more Nanoscaled so called indium tin oxide In 2 O 3 :Sn (ITO) with a specific BET surface area of 50 m 2 /g to 60 m 2 /g was prepared via an electrochemical method in an aqueous system containing ammonium acetate as conductive salt. As an intermediate product of the synthesis nanocrystalline In(OH) 3 is obtained which serves as a precursor for the subsequent calcinations accompanied by tin doping resulting in ITO powders with various tin concentrations. Its phase transitions and the reduction behaviour of hydroxide to oxide during the calcination process in air flow and forming gas atmosphere of N 2 to H 2 ratio of 95 to 5 respectively, have been investigated by high temperature X-ray diffraction, TG/DSC/MS, HRTEM and SEM analysis. Depending on the atmosphere dehydration of tin doped In(OH) 3 started at 150 C, cubic ITO solid solution formed between 190 C and 300 C. The total weight loss of the hydroxide of approx. 21% occurred mainly below 360 C and the burnout of organic components mainly between 308 C and 316 C. The results of DSC and MS analyses were in good agreement with the results of the X-ray diffraction. In addition, the products have been characterized by EDX associated with TEM, XPS, ICP-AES, BET analysis and 119 Sn Mössbauer spectroscopy. Completely reacted samples of ITO have been processed to pellets, calcined and sintered in the temperature range between 900 C and 1100 C and characterized by measurements of the electrical conductivities of bulk and surface in the reduced as well as in the oxidized state giving values up to 1400 Scm −1 .

ABSTRACT The AlGaN/GaN high electron mobility transistors (HEMTs) is a promising candidate for mi... more ABSTRACT The AlGaN/GaN high electron mobility transistors (HEMTs) is a promising candidate for microwave applications due to its high power and high temperature. owing to their large and direct band gap, as well as favorable transport properties. Moreover, III-V nitrides could be suitable for the emitters and detectors of green and shorter wavelengths, in turn making investments in this class of materials more than worthwhile. The electrical characteristics of metal contactst on-GaN have been examined by numerous research groups. The mechanism of leakage currents through GaN and AlGaN Schottky interfaces is discussed using temperature- dependent current-voltage (I-V-T) measurements, and found that the barrier thinning caused by unintentional surface-defect donors enhances the tunneling transport processes, leading to large leakage currents through GaN and AlGaN Schottky interfaces. Key world: AlGaN/GaN, HEMTs, I-V, Schottky barrier height, Barrier inhomogeneity.

ABSTRACT This paper reports on the use of plasma assisted molecular beam epitaxy of AlGaN/GaN hig... more ABSTRACT This paper reports on the use of plasma assisted molecular beam epitaxy of AlGaN/GaN high electron mobility transistors (HEMTs) grown on silicon substrate. Surface passivation effects on AlGaN/GaN HEMTs were studied using SiO 2 /SiN dielectric layers grown by plasma enhanced chemical vapor deposition. The direct current measurement, pulsed characteristics and microwave small-signal characteristics were studied before and after passivation. An improvement of drain-source current density and the extrinsic transconductance was observed on the passivated HEMTs when compared with the unpassivated HEMTs. An enhancement of cut-off frequency (f t) and maximum power gain (f max) was also observed for the devices with full SiO 2 /SiN passivation. A good correlation is found between pulsed and power measurements. Copyright © 2014 IFSA Publishing, S. L.

ABSTRACT Deep levels in AlGaN/GaN high electron mobility transistors (HEMTs) grown by molecular b... more ABSTRACT Deep levels in AlGaN/GaN high electron mobility transistors (HEMTs) grown by molecular beam epitaxy on silicon (Si) substrates were characterized by the means Capacitance-Voltage and Deep Level Transient Spectroscopy. DLTS Measurements have revealed four electron traps with the binding energies of 0.08, 0.25, 0.47 and 0.59 eV and capture cross-sections of 2.02×10 -18, 1.6×10-16, 1.2×10-12 and 7.02×1013cm2 respectively. The concentrations of the traps were found at around of 1014cm3. The nature and the localization of the traps have been discussed.

IOSR Journal of Applied Physics, 2014

The knowledge of the conduction mechanisms in a Schottky barrier is essential to calculate the Sc... more The knowledge of the conduction mechanisms in a Schottky barrier is essential to calculate the Schottky barrier parameters and to explain the observed effects. In the present work, we report temperaturedependent current-voltage characteristics of (Mo/Au)/Al 0.26 Ga 0.74 N/GaN/Si/ Schottky barrier diodes. Measurements were performed in the temperature range of 80-300 K.Results have been explained based on the thermionic emission mechanism with lateral inhomogeneity at the (Mo/Au/AlGaN/GaN/Si) interface. As is shown, the barrier height Φ B0 as well as the ideality factor n exhibit an important temperature dependence and the anomaly resulting from this dependence has been explained by invoking two sets of Gaussian distributions at the metal/semiconductor interface for temperature ranging from 80 K to 160 K and from 160K to300 K, respectively. It is also found that the values of R s obtained from Cheung's method strongly depend on temperature and decrease with decreasing temperature.

Materials Science in Semiconductor Processing, 2013

AlGaN/GaN/Si high electron mobility transistors (HEMTs) grown by molecular beam epitaxy are inves... more AlGaN/GaN/Si high electron mobility transistors (HEMTs) grown by molecular beam epitaxy are investigated using direct-current and radio-frequency measurements. As has been found, the maximum of drain current achieves 881 mA/mm with an extrinsic current gain cutoff frequency of 37 GHz for a 0.25 mm gate length. Pulsed characteristics also showed a reduction of trapping centers that improves the quality of the epilayers.

Superlattices and Microstructures, 2013

ABSTRACT The forward current-voltage I(V) characteristics of (Ni-Au)/ Al0.25Ga0.75N/GaN/SiC struc... more ABSTRACT The forward current-voltage I(V) characteristics of (Ni-Au)/ Al0.25Ga0.75N/GaN/SiC structures with differentSchottky contact areas were determined in the temperature range of 50-320K. The estimated values of ideality factor (n), zero-bias barrier height and series resistance (Rs) assuming thermionic emission (TE) show a temperature dependence of these parameters. Moreover, the conventional Richardson plot of versus for each sample shows two linear regions in the temperature ranges of 50-230K and 230-320K. The obtained Richardson constant values are lower than the theoretical value for Al0.25Ga0.75N. Such behavior was attributed to Schottky barrier inhomogeneities by assuming a double Gaussian distribution (GD) of the barrier heights (BHs) at the (Ni-Au)/Al0.25Ga0.75N interface. We attempted to draw versus plot in order to obtain evidence of the double GD of BHs for each sample. Therefore, the temperature dependence of the forward I(V)characteristics can be successfully explained on the basis of the TE theory with a double GD of the BHs at (Ni-Au)/Al0.25Ga0.75N interface. These results suggest that the lateral inhomogeneity of the Schottky barrier height (SBH) is connected to the non-uniform distribution of surface and/or interface states. This non-uniformity is attributed to the presence of defects which confirms the results already obtained by capacitance deep level transient spectroscopy (DLTS) technique.

Sensor Letters, 2011

Abstract: Reliability issues such as degradation of DC and transient characteristics have been in... more Abstract: Reliability issues such as degradation of DC and transient characteristics have been intensively investigated in AlGaN/GaN HEMT on Al 2 O 3 substrates. The instability of AlGaN/GaN HEMT operations is attributed to modification in electrical behavior of trapping ...

Sensor Letters, 2011

Abstract: In this paper we present static measurements and defect analysis performed on AlGaN/GaN... more Abstract: In this paper we present static measurements and defect analysis performed on AlGaN/GaN/SiC HEMTs. I dV ds and I gV gs characteristics show anomalies like: leakage current, degradation on saturation current, hysteresis effect and kink effect. These ...

Semiconductors, 2012

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 low frequency noise. This work demonstrates the effect of surface passivation on the current-voltage character istics 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.

Semiconductors, 2013

ABSTRACT Device performance and defects in AlGaN/GaN high-electron mobility transistors have been... more ABSTRACT Device performance and defects in AlGaN/GaN high-electron mobility transistors have been correlated. The effect of SiN/SiO2 passivation of the surface of AlGaN/GaN high-electron mobility transistors on Si substrates is reported on DC characteristics. Deep level transient spectroscopy (DLTS) measurements were performed on the device after the passivation by a (50/100 nm) SiN/SiO2 film. The DLTS spectra from these measurements showed the existence of the same electron trap on the surface of the device.

Semiconductor Science and Technology, 2006

We report on the application of the deep level transient spectroscopy technique to the study of h... more We report on the application of the deep level transient spectroscopy technique to the study of hole emission from the confined energy levels in quantum dots. The results are presented for self-assembled InAs quantum dots grown on p-type InAlAs barrier layers, lattice matched to an InP(0 0 1) substrate. Two deep levels, linked to the quantum dots, are detected, indicative

Physica B: Condensed Matter, 2010

Deep levels behaviors in AlGaN/GaN high electron mobility transistors (HEMTs) with sapphire (Al2O... more Deep levels behaviors in AlGaN/GaN high electron mobility transistors (HEMTs) with sapphire (Al2O3) substrates were characterized by the means of conductance deep level transient spectroscopy (CDLTS) under a gate pulse. Five electron traps have been detected in our sample with activation energy and capture cross-section of 1.3, 1.12, 1.06, 0.22, 0.18eV and σn=2.2×10−12cm2, σn=2.1×10−17cm2, σn=1.5×10−15cm2, σn=3.1×10−15cm2, σn=5×10−13cm2, respectively. The nature

Physica B: Condensed Matter, 2013

Hysteresis phenomenon in the capacitance-voltage characteristics and leakage current under revers... more Hysteresis phenomenon in the capacitance-voltage characteristics and leakage current under reversebiased Schottky gate were investigated for Al 0.25 Ga 0.75 N/GaN/SiC HEMT's with two different gate lengths. These phenomena were attributed to the electron tunneling through the surface, the bulk or/ and the metal/AlGaN interface states. Using Capacitance DLTS, we have found that the deep trap responsible of these phenomena has activation energy of 0.74 eV. It was an extended defect in the AlGaN/GaN heterostructures. Else, an electron trap (Ea ¼0.16 eV) was detected only in the transistor having the smaller gate length. The possible explanations of its origin will be established in this paper.

Journal of sol-gel science and technology, May 21, 2024

Journal of Ovonic Research

When the AlGaN/GaN high electron mobility transistor (HEMT) is strongly biased, the speed of the ... more When the AlGaN/GaN high electron mobility transistor (HEMT) is strongly biased, the speed of the electrons in the channel increases, which leads to an injection of electrons into the buffer, and consequently the appearance of the "short channel effect" phenomenon, which limits the performance of the component to overcome this effect and increase the power/frequency performance of the component, one solution consists in using a confinement barrier. This involves placing an electrostatic barrier under the GaN channel so as to block the injection of electrons into the buffer layer when the transistor is highly biased, and a BGaN confinement barrier because this semiconductor has very interesting physical properties, as well as better electrical isolation between the well and the substrate thanks to the optimization of the buffer. In this paper, the main objective is to study the effect of adding BGaN confinement barrier and its influence on transistor performance.

Journal of Ovonic Research

AlGaN/GaN/Si HEMTs have been investigated using current-voltage-temperature and CDLTS measurement... more AlGaN/GaN/Si HEMTs have been investigated using current-voltage-temperature and CDLTS measurements.As has been found from current voltage measurements, parasitic effects were revealed indicating the presence of traps in HEMT device. As a result, the origins of traps are determined from CDLTS experiments.

Ceramics International, 2002

Nanoscaled so called indium tin oxide In 2 O 3 :Sn (ITO) with a specific BET surface area of 50 m... more Nanoscaled so called indium tin oxide In 2 O 3 :Sn (ITO) with a specific BET surface area of 50 m 2 /g to 60 m 2 /g was prepared via an electrochemical method in an aqueous system containing ammonium acetate as conductive salt. As an intermediate product of the synthesis nanocrystalline In(OH) 3 is obtained which serves as a precursor for the subsequent calcinations accompanied by tin doping resulting in ITO powders with various tin concentrations. Its phase transitions and the reduction behaviour of hydroxide to oxide during the calcination process in air flow and forming gas atmosphere of N 2 to H 2 ratio of 95 to 5 respectively, have been investigated by high temperature X-ray diffraction, TG/DSC/MS, HRTEM and SEM analysis. Depending on the atmosphere dehydration of tin doped In(OH) 3 started at 150 C, cubic ITO solid solution formed between 190 C and 300 C. The total weight loss of the hydroxide of approx. 21% occurred mainly below 360 C and the burnout of organic components mainly between 308 C and 316 C. The results of DSC and MS analyses were in good agreement with the results of the X-ray diffraction. In addition, the products have been characterized by EDX associated with TEM, XPS, ICP-AES, BET analysis and 119 Sn Mössbauer spectroscopy. Completely reacted samples of ITO have been processed to pellets, calcined and sintered in the temperature range between 900 C and 1100 C and characterized by measurements of the electrical conductivities of bulk and surface in the reduced as well as in the oxidized state giving values up to 1400 Scm −1 .

ABSTRACT The AlGaN/GaN high electron mobility transistors (HEMTs) is a promising candidate for mi... more ABSTRACT The AlGaN/GaN high electron mobility transistors (HEMTs) is a promising candidate for microwave applications due to its high power and high temperature. owing to their large and direct band gap, as well as favorable transport properties. Moreover, III-V nitrides could be suitable for the emitters and detectors of green and shorter wavelengths, in turn making investments in this class of materials more than worthwhile. The electrical characteristics of metal contactst on-GaN have been examined by numerous research groups. The mechanism of leakage currents through GaN and AlGaN Schottky interfaces is discussed using temperature- dependent current-voltage (I-V-T) measurements, and found that the barrier thinning caused by unintentional surface-defect donors enhances the tunneling transport processes, leading to large leakage currents through GaN and AlGaN Schottky interfaces. Key world: AlGaN/GaN, HEMTs, I-V, Schottky barrier height, Barrier inhomogeneity.

ABSTRACT This paper reports on the use of plasma assisted molecular beam epitaxy of AlGaN/GaN hig... more ABSTRACT This paper reports on the use of plasma assisted molecular beam epitaxy of AlGaN/GaN high electron mobility transistors (HEMTs) grown on silicon substrate. Surface passivation effects on AlGaN/GaN HEMTs were studied using SiO 2 /SiN dielectric layers grown by plasma enhanced chemical vapor deposition. The direct current measurement, pulsed characteristics and microwave small-signal characteristics were studied before and after passivation. An improvement of drain-source current density and the extrinsic transconductance was observed on the passivated HEMTs when compared with the unpassivated HEMTs. An enhancement of cut-off frequency (f t) and maximum power gain (f max) was also observed for the devices with full SiO 2 /SiN passivation. A good correlation is found between pulsed and power measurements. Copyright © 2014 IFSA Publishing, S. L.

ABSTRACT Deep levels in AlGaN/GaN high electron mobility transistors (HEMTs) grown by molecular b... more ABSTRACT Deep levels in AlGaN/GaN high electron mobility transistors (HEMTs) grown by molecular beam epitaxy on silicon (Si) substrates were characterized by the means Capacitance-Voltage and Deep Level Transient Spectroscopy. DLTS Measurements have revealed four electron traps with the binding energies of 0.08, 0.25, 0.47 and 0.59 eV and capture cross-sections of 2.02×10 -18, 1.6×10-16, 1.2×10-12 and 7.02×1013cm2 respectively. The concentrations of the traps were found at around of 1014cm3. The nature and the localization of the traps have been discussed.

IOSR Journal of Applied Physics, 2014

The knowledge of the conduction mechanisms in a Schottky barrier is essential to calculate the Sc... more The knowledge of the conduction mechanisms in a Schottky barrier is essential to calculate the Schottky barrier parameters and to explain the observed effects. In the present work, we report temperaturedependent current-voltage characteristics of (Mo/Au)/Al 0.26 Ga 0.74 N/GaN/Si/ Schottky barrier diodes. Measurements were performed in the temperature range of 80-300 K.Results have been explained based on the thermionic emission mechanism with lateral inhomogeneity at the (Mo/Au/AlGaN/GaN/Si) interface. As is shown, the barrier height Φ B0 as well as the ideality factor n exhibit an important temperature dependence and the anomaly resulting from this dependence has been explained by invoking two sets of Gaussian distributions at the metal/semiconductor interface for temperature ranging from 80 K to 160 K and from 160K to300 K, respectively. It is also found that the values of R s obtained from Cheung's method strongly depend on temperature and decrease with decreasing temperature.

Materials Science in Semiconductor Processing, 2013

AlGaN/GaN/Si high electron mobility transistors (HEMTs) grown by molecular beam epitaxy are inves... more AlGaN/GaN/Si high electron mobility transistors (HEMTs) grown by molecular beam epitaxy are investigated using direct-current and radio-frequency measurements. As has been found, the maximum of drain current achieves 881 mA/mm with an extrinsic current gain cutoff frequency of 37 GHz for a 0.25 mm gate length. Pulsed characteristics also showed a reduction of trapping centers that improves the quality of the epilayers.

Superlattices and Microstructures, 2013

ABSTRACT The forward current-voltage I(V) characteristics of (Ni-Au)/ Al0.25Ga0.75N/GaN/SiC struc... more ABSTRACT The forward current-voltage I(V) characteristics of (Ni-Au)/ Al0.25Ga0.75N/GaN/SiC structures with differentSchottky contact areas were determined in the temperature range of 50-320K. The estimated values of ideality factor (n), zero-bias barrier height and series resistance (Rs) assuming thermionic emission (TE) show a temperature dependence of these parameters. Moreover, the conventional Richardson plot of versus for each sample shows two linear regions in the temperature ranges of 50-230K and 230-320K. The obtained Richardson constant values are lower than the theoretical value for Al0.25Ga0.75N. Such behavior was attributed to Schottky barrier inhomogeneities by assuming a double Gaussian distribution (GD) of the barrier heights (BHs) at the (Ni-Au)/Al0.25Ga0.75N interface. We attempted to draw versus plot in order to obtain evidence of the double GD of BHs for each sample. Therefore, the temperature dependence of the forward I(V)characteristics can be successfully explained on the basis of the TE theory with a double GD of the BHs at (Ni-Au)/Al0.25Ga0.75N interface. These results suggest that the lateral inhomogeneity of the Schottky barrier height (SBH) is connected to the non-uniform distribution of surface and/or interface states. This non-uniformity is attributed to the presence of defects which confirms the results already obtained by capacitance deep level transient spectroscopy (DLTS) technique.

Sensor Letters, 2011

Abstract: Reliability issues such as degradation of DC and transient characteristics have been in... more Abstract: Reliability issues such as degradation of DC and transient characteristics have been intensively investigated in AlGaN/GaN HEMT on Al 2 O 3 substrates. The instability of AlGaN/GaN HEMT operations is attributed to modification in electrical behavior of trapping ...

Sensor Letters, 2011

Abstract: In this paper we present static measurements and defect analysis performed on AlGaN/GaN... more Abstract: In this paper we present static measurements and defect analysis performed on AlGaN/GaN/SiC HEMTs. I dV ds and I gV gs characteristics show anomalies like: leakage current, degradation on saturation current, hysteresis effect and kink effect. These ...

Semiconductors, 2012

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 low frequency noise. This work demonstrates the effect of surface passivation on the current-voltage character istics 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.

Semiconductors, 2013

ABSTRACT Device performance and defects in AlGaN/GaN high-electron mobility transistors have been... more ABSTRACT Device performance and defects in AlGaN/GaN high-electron mobility transistors have been correlated. The effect of SiN/SiO2 passivation of the surface of AlGaN/GaN high-electron mobility transistors on Si substrates is reported on DC characteristics. Deep level transient spectroscopy (DLTS) measurements were performed on the device after the passivation by a (50/100 nm) SiN/SiO2 film. The DLTS spectra from these measurements showed the existence of the same electron trap on the surface of the device.

Semiconductor Science and Technology, 2006

We report on the application of the deep level transient spectroscopy technique to the study of h... more We report on the application of the deep level transient spectroscopy technique to the study of hole emission from the confined energy levels in quantum dots. The results are presented for self-assembled InAs quantum dots grown on p-type InAlAs barrier layers, lattice matched to an InP(0 0 1) substrate. Two deep levels, linked to the quantum dots, are detected, indicative

Physica B: Condensed Matter, 2010

Deep levels behaviors in AlGaN/GaN high electron mobility transistors (HEMTs) with sapphire (Al2O... more Deep levels behaviors in AlGaN/GaN high electron mobility transistors (HEMTs) with sapphire (Al2O3) substrates were characterized by the means of conductance deep level transient spectroscopy (CDLTS) under a gate pulse. Five electron traps have been detected in our sample with activation energy and capture cross-section of 1.3, 1.12, 1.06, 0.22, 0.18eV and σn=2.2×10−12cm2, σn=2.1×10−17cm2, σn=1.5×10−15cm2, σn=3.1×10−15cm2, σn=5×10−13cm2, respectively. The nature

Physica B: Condensed Matter, 2013

Hysteresis phenomenon in the capacitance-voltage characteristics and leakage current under revers... more Hysteresis phenomenon in the capacitance-voltage characteristics and leakage current under reversebiased Schottky gate were investigated for Al 0.25 Ga 0.75 N/GaN/SiC HEMT's with two different gate lengths. These phenomena were attributed to the electron tunneling through the surface, the bulk or/ and the metal/AlGaN interface states. Using Capacitance DLTS, we have found that the deep trap responsible of these phenomena has activation energy of 0.74 eV. It was an extended defect in the AlGaN/GaN heterostructures. Else, an electron trap (Ea ¼0.16 eV) was detected only in the transistor having the smaller gate length. The possible explanations of its origin will be established in this paper.