Asif Khan - Academia.edu (original) (raw)

Papers by Asif Khan

Research paper thumbnail of TPD1-like Gene as a Suitable Marker for Early Sex Determination in Date Palm (Phoenix dactylifera L.)

Genes

Date palm (Phoenix dactylifera L.) is a considerably beneficial and economically profitable fruit... more Date palm (Phoenix dactylifera L.) is a considerably beneficial and economically profitable fruit crop. Female date palm plants produce fruit that is rich in fiber and sugar. Date palm is propagated by two means: suckers and seed. The propagation of date palm through seeds is very necessary for germplasm conservation and breeding. The late reproductive age (4–5 years) and dioecious nature of date palm make genetic improvement and breeding difficult. Early sex determination is the only way to improve breeding by selecting experimental male and female plants at the seedling stage. The primers for Tapetum Determinant 1 (TPD1-like) were designed using Amplify software. The DNA amplification of selected date palm suckers of three genotypes (Ajwa, Amber, and Medjool) was observed through PCR. Expression profiling of selected genotypes was carried out through semi-q PCR and RT-PCR by using the cDNA of suckers and unknown seedlings. Different in silico analyses were performed for the gene a...

Research paper thumbnail of Genome editing in cotton: challenges and opportunities

Journal of Cotton Research

Cotton has enormous economic potential providing high-quality protein, oil, and fibre. A large in... more Cotton has enormous economic potential providing high-quality protein, oil, and fibre. A large increase in cotton output is necessary due to the world's changing climate and constantly expanding human population. In the past, conventional breeding techniques were used to introduce genes into superior cotton cultivars to increase production and to improve quality. The disadvantages of traditional breeding techniques are their time-consuming, reliance on genetic differences that are already present, and considerable backcrossing. To accomplish goals in a short amount of time, contemporary plant breeding techniques, in particular modern genome editing technologies (GETs), can be used. Numerous crop improvement initiatives have made use of GETs, such as zinc-finger nucleases, transcription-activator-like effector nucleases, clustered regularly interspaced palindromic repeats (CRISPR), and CRISPR-associated proteins systems (CRISPR/Cas)-based technologies. The CRISPR/Cas system has a...

Research paper thumbnail of COTIP: Cotton TILLING Platform, a Resource for Plant Improvement and Reverse Genetic Studies

Frontiers in plant science, 2016

Cotton is cultivated worldwide for its white fiber, of which around 90% is tetraploid upland cott... more Cotton is cultivated worldwide for its white fiber, of which around 90% is tetraploid upland cotton (Gossypium hirsutum L.) carrying both A and D genome. Since centuries, yield increasing efforts for the cotton crop by conventional breeding approaches have caused an extensive erosion of natural genetic variability. Mutation based improvement strategies provide an effective way of creating new allelic variations. Targeting Induced Local Lesions IN Genomes (TILLING) provides a mutation based reverse genetic strategy to create and evaluate induced genetic variability at DNA level. Here, we report development and testing of TILLING populations of allotetraploid cotton (G. hirsutum) for functional genomic studies and mutation based enrichment of cotton genetic resources. Seed of two cotton cultivars "PB-899 and PB-900" were mutagenized with 0.3 and 0.2% (v/v) ethyl methanesulfonate, respectively. The phenotyping of M1 and M2 populations presented numerous mutants regarding the ...

Research paper thumbnail of Molecular Screening of Cotton Germplasm for Cotton Leaf Curl Disease Caused by Viral Strains

International Journal of Agriculture and Biology, 2017

Research paper thumbnail of Genetic basis of variation for seedling traits in Gossypium hirsutum L

African Journal of Biotechnology, Feb 14, 2011

Research paper thumbnail of From Qutn to Bt cotton: Development, adoption and prospects. A review

Cytology and Genetics, 2015

Cotton has unique history of domestication, diversification, and utilization. Globally it is an i... more Cotton has unique history of domestication, diversification, and utilization. Globally it is an important cash crop that provides raw material for textile industry. The story of cotton started from human civilization and the climax arrived with the efforts of developing transgenic cotton for various traits. Though conventional breeding brought steady improvement in developing resistance against biotic stresses but recent success story of gene transferfrom Bacillus thuringiensis into cotton showed game changing effects on cotton cultivation. Amongst various families of insecticidal proteins Bt Cry-toxins received more attention because of specificity against receptors on the cell membranes of insect midgut epithelial cells. Rapid Bt cotton adoption by farmers due to its economic and environmental benefits has changed the landscape of cotton cultivation in many countries. But the variable expression of Bt transgene in the newly developed Bt cotton genotypes in tropical environment is questionable. Variability of toxin level in different plant parts at various life stage of plant is an outcome of genotypic interaction with environmental factors. Temporal gene expression of Cry1Ac is also blamed for the epigenetic background in which transgene has been inserted. The presence of genotypes with sub-lethal level of Bt toxin might create resistance in Lepidopteron insects, limiting the use of Bt cotton in future, with the opportunityfor other resistance development strategies to get more attention like gene stacking. Until the farmers get access to more recent technology, best option is to delay the development of resistance by applying Insect Resistance Management (IRM) strategies.

Research paper thumbnail of Negative Differential Conductivity in AlGaN/GaN HEMTs: Real Space Charge Transfer from 2D to 3D GaN States?

MRS Proceedings, 1999

We report on non-thermal negative differential conductivity (NDC) in AlGaN/GaN HEMTs grown on sap... more We report on non-thermal negative differential conductivity (NDC) in AlGaN/GaN HEMTs grown on sapphire substrates by low-pressure MOCVD. The sheet electron density was on the order of few times 1012cm−2 and the Hall mobility was 1,000 cm2/V.s. The HEMTs had threshold voltage close to zero and could operate at high positive gate bias up to 3 to 3.5 Volts, with a very low gate leakage current. NDC was observed at the gate bias larger than 1.5V and at the drain biases between approximately 0.5Vg and Vg. We excluded the possibility of self-heating as the cause, since the NDC occurs at relatively small power levels where self-heating effects are negligible.An explanation we provided for the NDC effect is the new mechanism of real space charge transfer from 2D to 3D GaN states, which leads to a decrease in the channel mobility at large 2D electron gas densities. The observed low leakage can be explained by an enhanced molar fraction of aluminum at the heterointerface that results in a lar...

Research paper thumbnail of <title>Generation-recombination noise in GaN and GaN-based devices</title>

Noise in Devices and Circuits, 2003

Research paper thumbnail of AlGaN/GaN HEMT high-power and low-noise performance at f≥20 GHz

Proceedings. IEEE Lester Eastman Conference on High Performance Devices

In this paper, we report on the power and noise performance of A1GaN/GaN HEMTs in the K (18-27 GH... more In this paper, we report on the power and noise performance of A1GaN/GaN HEMTs in the K (18-27 GHz) band. At 20 GHz, a record CW output power of 2 W with an associated gain of 8 dB and PAE of 33 % has been achieved on a 8-finger 0.2 pm x 500 gm device. Minimum noise figure of 1.4 dB has been achieved on a 0.15 gm x 200 gm device at 26 GHz. The data demonstrate the viability of AIGaN/GaN HEMTs for high-frequency power and LNA applications.

Research paper thumbnail of Molecular Markers and Cotton Genetic Improvement: Current Status and Future Prospects

The Scientific World Journal, 2014

Narrow genetic base and complex allotetraploid genome of cotton (Gossypium hirsutumL.) is stimula... more Narrow genetic base and complex allotetraploid genome of cotton (Gossypium hirsutumL.) is stimulating efforts to avail required polymorphism for marker based breeding. The availability of draft genome sequence ofG. raimondiiandG. arboreumand next generation sequencing (NGS) technologies facilitated the development of high-throughput marker technologies in cotton. The concepts of genetic diversity, QTL mapping, and marker assisted selection (MAS) are evolving into more efficient concepts of linkage disequilibrium, association mapping, and genomic selection, respectively. The objective of the current review is to analyze the pace of evolution in the molecular marker technologies in cotton during the last ten years into the following four areas: (i) comparative analysis of low- and high-throughput marker technologies available in cotton, (ii) genetic diversity in the available wild and improved gene pools of cotton, (iii) identification of the genomic regions within cotton genome under...

Research paper thumbnail of An assessment of wide bandgap semiconductors for power devices

IEEE Transactions on Power Electronics, 2003

An advantage for some wide bandgap materials, that is often overlooked, is that the thermal coeff... more An advantage for some wide bandgap materials, that is often overlooked, is that the thermal coefficient of expansion (CTE) is better matched to the ceramics in use for packaging technology. It is shown that the optimal choice for uni-polar devices is clearly GaN. It is further shown that the future optimal choice for bipolar devices is C (diamond) owing to the large bandgap, high thermal conductivity, and large electron and hole mobilities. A new expression relating the critical electric field for breakdown in abrupt junctions to the material bandgap energy is derived and is further used to derive new expressions for specific on-resistance in power semiconductor devices. These new expressions are compared to the previous literature and the efficacy of specific power devices, such as heterojunction MOSFETs, using GaN are discussed.

Research paper thumbnail of AlGaN/GaN HEMTs on SiC with over 100 GHz f/sub T/ and low microwave noise

IEEE Transactions on Electron Devices, 2001

Research paper thumbnail of Millimeter-wave high-power 0.25-/spl mu/m gate-length AlGaN/GaN HEMTs on SiC substrates

IEEE Microwave and Wireless Components Letters, 2003

We report on the CW power performance at 20 and 30 GHz of 0.25 m 100 m AlGaN/GaN high electron mo... more We report on the CW power performance at 20 and 30 GHz of 0.25 m 100 m AlGaN/GaN high electron mobility transistors (HEMTs) grown by MOCVD on semi-insulating SiC substrates. The devices exhibited current density of 1300 mA/mm, peak dc extrinsic transconductance of 275 mS/mm, unity current gain cutoff () of 65 GHz, and maximum frequency of oscillation (max) of 110 GHz. Saturated output power at 20 GHz was 6.4 W/mm with 16% power added efficiency (PAE), and output power at 1-dB compression at 30 GHz was 4.0 W/mm with 20% PAE. This is the highest power reported for 0.25-m gate-length devices at 20 GHz, and the 30 GHz results represent the highest frequency power data published to date on GaN-based devices.

Research paper thumbnail of The 1.6-kV AlGaN/GaN HFETs

IEEE Electron Device Letters, 2006

The breakdown voltages in unpassivated nonfieldplated AlGaN/GaN HFETs on sapphire substrates were... more The breakdown voltages in unpassivated nonfieldplated AlGaN/GaN HFETs on sapphire substrates were studied. These studies reveal that the breakdown is limited by the surface flashover rather than by the AlGaN/GaN channel. After elimination of the surface flashover in air, the breakdown voltage scaled linearly with the gate-drain spacing reaching 1.6 kV at 20 µm. The corresponding static ON-resistance was as low as 3.4 mΩ • cm 2. This translates to a power device figure-of-merit V 2 BR /R ON = 7.5 × 10 8 V 2 • Ω −1 cm −2 , which, to date, is among the best reported values for an AlGaN/GaN HFET.

Research paper thumbnail of Silicon Dioxide-Encapsulated High-Voltage AlGaN/GaN HFETs for Power-Switching Applications

IEEE Electron Device Letters, 2007

Research paper thumbnail of DC and microwave performance of high-current AlGaN/GaN heterostructure field effect transistors grown on p-type SiC substrates

IEEE Electron Device Letters, 1998

Research paper thumbnail of AlGaN/GaN HEMTs on SiC with f/sub T/ of over 120 GHz

IEEE Electron Device Letters, 2002

AlGaN/GaN high electron mobility transistors (HEMTs) grown on semi-insulating SiC substrates with... more AlGaN/GaN high electron mobility transistors (HEMTs) grown on semi-insulating SiC substrates with a 0.12 m gate length have been fabricated. These 0.12m gate-length devices exhibited maximum drain current density as high as 1.23 A/mm and peak extrinsic transconductance of 314 mS/mm. The threshold voltage was 5.2 V. A unity current gain cutoff frequency () of 121 GHz and maximum frequency of oscillation (max) of 162 GHz were measured on these devices. These and max values are the highest ever reported values for GaN-based HEMTs.

Research paper thumbnail of Low-loss high power RF switching using multifinger AlGaN/GaN MOSHFETs

IEEE Electron Device Letters, 2002

Research paper thumbnail of AlGaN-GaN HEMTs on SiC with CW power performance of >4 W/mm and 23% PAE at 35 GHz

IEEE Electron Device Letters, 2003

In this letter, continuous wave-band power performance of AlGaN-GaN high electron-mobility transi... more In this letter, continuous wave-band power performance of AlGaN-GaN high electron-mobility transistors grown on semi-insulating SiC substrates are reported. The devices, with gate lengths of 0.25 m, exhibited maximum drain current density of 1.1 A/mm and peak extrinsic transconductance of 285 mS/mm. At 35 GHz, an output power density of 4.13 W/mm with 23% of power-added efficiency (PAE) and 7.54 dB of linear gain were achieved at a drain bias of 30 V. These power results represent the best power density, PAE, and gain combination reported at this frequency. The drain bias dependence of the-band power performance of these devices is also presented. Index Terms-AlGaN, GaN, microwave power high electron mobility transistors (HEMTs).

Research paper thumbnail of Thermal management of AlGaN-GaN HFETs on sapphire using flip-chip bonding with epoxy underfill

IEEE Electron Device Letters, 2003

Research paper thumbnail of TPD1-like Gene as a Suitable Marker for Early Sex Determination in Date Palm (Phoenix dactylifera L.)

Genes

Date palm (Phoenix dactylifera L.) is a considerably beneficial and economically profitable fruit... more Date palm (Phoenix dactylifera L.) is a considerably beneficial and economically profitable fruit crop. Female date palm plants produce fruit that is rich in fiber and sugar. Date palm is propagated by two means: suckers and seed. The propagation of date palm through seeds is very necessary for germplasm conservation and breeding. The late reproductive age (4–5 years) and dioecious nature of date palm make genetic improvement and breeding difficult. Early sex determination is the only way to improve breeding by selecting experimental male and female plants at the seedling stage. The primers for Tapetum Determinant 1 (TPD1-like) were designed using Amplify software. The DNA amplification of selected date palm suckers of three genotypes (Ajwa, Amber, and Medjool) was observed through PCR. Expression profiling of selected genotypes was carried out through semi-q PCR and RT-PCR by using the cDNA of suckers and unknown seedlings. Different in silico analyses were performed for the gene a...

Research paper thumbnail of Genome editing in cotton: challenges and opportunities

Journal of Cotton Research

Cotton has enormous economic potential providing high-quality protein, oil, and fibre. A large in... more Cotton has enormous economic potential providing high-quality protein, oil, and fibre. A large increase in cotton output is necessary due to the world's changing climate and constantly expanding human population. In the past, conventional breeding techniques were used to introduce genes into superior cotton cultivars to increase production and to improve quality. The disadvantages of traditional breeding techniques are their time-consuming, reliance on genetic differences that are already present, and considerable backcrossing. To accomplish goals in a short amount of time, contemporary plant breeding techniques, in particular modern genome editing technologies (GETs), can be used. Numerous crop improvement initiatives have made use of GETs, such as zinc-finger nucleases, transcription-activator-like effector nucleases, clustered regularly interspaced palindromic repeats (CRISPR), and CRISPR-associated proteins systems (CRISPR/Cas)-based technologies. The CRISPR/Cas system has a...

Research paper thumbnail of COTIP: Cotton TILLING Platform, a Resource for Plant Improvement and Reverse Genetic Studies

Frontiers in plant science, 2016

Cotton is cultivated worldwide for its white fiber, of which around 90% is tetraploid upland cott... more Cotton is cultivated worldwide for its white fiber, of which around 90% is tetraploid upland cotton (Gossypium hirsutum L.) carrying both A and D genome. Since centuries, yield increasing efforts for the cotton crop by conventional breeding approaches have caused an extensive erosion of natural genetic variability. Mutation based improvement strategies provide an effective way of creating new allelic variations. Targeting Induced Local Lesions IN Genomes (TILLING) provides a mutation based reverse genetic strategy to create and evaluate induced genetic variability at DNA level. Here, we report development and testing of TILLING populations of allotetraploid cotton (G. hirsutum) for functional genomic studies and mutation based enrichment of cotton genetic resources. Seed of two cotton cultivars "PB-899 and PB-900" were mutagenized with 0.3 and 0.2% (v/v) ethyl methanesulfonate, respectively. The phenotyping of M1 and M2 populations presented numerous mutants regarding the ...

Research paper thumbnail of Molecular Screening of Cotton Germplasm for Cotton Leaf Curl Disease Caused by Viral Strains

International Journal of Agriculture and Biology, 2017

Research paper thumbnail of Genetic basis of variation for seedling traits in Gossypium hirsutum L

African Journal of Biotechnology, Feb 14, 2011

Research paper thumbnail of From Qutn to Bt cotton: Development, adoption and prospects. A review

Cytology and Genetics, 2015

Cotton has unique history of domestication, diversification, and utilization. Globally it is an i... more Cotton has unique history of domestication, diversification, and utilization. Globally it is an important cash crop that provides raw material for textile industry. The story of cotton started from human civilization and the climax arrived with the efforts of developing transgenic cotton for various traits. Though conventional breeding brought steady improvement in developing resistance against biotic stresses but recent success story of gene transferfrom Bacillus thuringiensis into cotton showed game changing effects on cotton cultivation. Amongst various families of insecticidal proteins Bt Cry-toxins received more attention because of specificity against receptors on the cell membranes of insect midgut epithelial cells. Rapid Bt cotton adoption by farmers due to its economic and environmental benefits has changed the landscape of cotton cultivation in many countries. But the variable expression of Bt transgene in the newly developed Bt cotton genotypes in tropical environment is questionable. Variability of toxin level in different plant parts at various life stage of plant is an outcome of genotypic interaction with environmental factors. Temporal gene expression of Cry1Ac is also blamed for the epigenetic background in which transgene has been inserted. The presence of genotypes with sub-lethal level of Bt toxin might create resistance in Lepidopteron insects, limiting the use of Bt cotton in future, with the opportunityfor other resistance development strategies to get more attention like gene stacking. Until the farmers get access to more recent technology, best option is to delay the development of resistance by applying Insect Resistance Management (IRM) strategies.

Research paper thumbnail of Negative Differential Conductivity in AlGaN/GaN HEMTs: Real Space Charge Transfer from 2D to 3D GaN States?

MRS Proceedings, 1999

We report on non-thermal negative differential conductivity (NDC) in AlGaN/GaN HEMTs grown on sap... more We report on non-thermal negative differential conductivity (NDC) in AlGaN/GaN HEMTs grown on sapphire substrates by low-pressure MOCVD. The sheet electron density was on the order of few times 1012cm−2 and the Hall mobility was 1,000 cm2/V.s. The HEMTs had threshold voltage close to zero and could operate at high positive gate bias up to 3 to 3.5 Volts, with a very low gate leakage current. NDC was observed at the gate bias larger than 1.5V and at the drain biases between approximately 0.5Vg and Vg. We excluded the possibility of self-heating as the cause, since the NDC occurs at relatively small power levels where self-heating effects are negligible.An explanation we provided for the NDC effect is the new mechanism of real space charge transfer from 2D to 3D GaN states, which leads to a decrease in the channel mobility at large 2D electron gas densities. The observed low leakage can be explained by an enhanced molar fraction of aluminum at the heterointerface that results in a lar...

Research paper thumbnail of <title>Generation-recombination noise in GaN and GaN-based devices</title>

Noise in Devices and Circuits, 2003

Research paper thumbnail of AlGaN/GaN HEMT high-power and low-noise performance at f≥20 GHz

Proceedings. IEEE Lester Eastman Conference on High Performance Devices

In this paper, we report on the power and noise performance of A1GaN/GaN HEMTs in the K (18-27 GH... more In this paper, we report on the power and noise performance of A1GaN/GaN HEMTs in the K (18-27 GHz) band. At 20 GHz, a record CW output power of 2 W with an associated gain of 8 dB and PAE of 33 % has been achieved on a 8-finger 0.2 pm x 500 gm device. Minimum noise figure of 1.4 dB has been achieved on a 0.15 gm x 200 gm device at 26 GHz. The data demonstrate the viability of AIGaN/GaN HEMTs for high-frequency power and LNA applications.

Research paper thumbnail of Molecular Markers and Cotton Genetic Improvement: Current Status and Future Prospects

The Scientific World Journal, 2014

Narrow genetic base and complex allotetraploid genome of cotton (Gossypium hirsutumL.) is stimula... more Narrow genetic base and complex allotetraploid genome of cotton (Gossypium hirsutumL.) is stimulating efforts to avail required polymorphism for marker based breeding. The availability of draft genome sequence ofG. raimondiiandG. arboreumand next generation sequencing (NGS) technologies facilitated the development of high-throughput marker technologies in cotton. The concepts of genetic diversity, QTL mapping, and marker assisted selection (MAS) are evolving into more efficient concepts of linkage disequilibrium, association mapping, and genomic selection, respectively. The objective of the current review is to analyze the pace of evolution in the molecular marker technologies in cotton during the last ten years into the following four areas: (i) comparative analysis of low- and high-throughput marker technologies available in cotton, (ii) genetic diversity in the available wild and improved gene pools of cotton, (iii) identification of the genomic regions within cotton genome under...

Research paper thumbnail of An assessment of wide bandgap semiconductors for power devices

IEEE Transactions on Power Electronics, 2003

An advantage for some wide bandgap materials, that is often overlooked, is that the thermal coeff... more An advantage for some wide bandgap materials, that is often overlooked, is that the thermal coefficient of expansion (CTE) is better matched to the ceramics in use for packaging technology. It is shown that the optimal choice for uni-polar devices is clearly GaN. It is further shown that the future optimal choice for bipolar devices is C (diamond) owing to the large bandgap, high thermal conductivity, and large electron and hole mobilities. A new expression relating the critical electric field for breakdown in abrupt junctions to the material bandgap energy is derived and is further used to derive new expressions for specific on-resistance in power semiconductor devices. These new expressions are compared to the previous literature and the efficacy of specific power devices, such as heterojunction MOSFETs, using GaN are discussed.

Research paper thumbnail of AlGaN/GaN HEMTs on SiC with over 100 GHz f/sub T/ and low microwave noise

IEEE Transactions on Electron Devices, 2001

Research paper thumbnail of Millimeter-wave high-power 0.25-/spl mu/m gate-length AlGaN/GaN HEMTs on SiC substrates

IEEE Microwave and Wireless Components Letters, 2003

We report on the CW power performance at 20 and 30 GHz of 0.25 m 100 m AlGaN/GaN high electron mo... more We report on the CW power performance at 20 and 30 GHz of 0.25 m 100 m AlGaN/GaN high electron mobility transistors (HEMTs) grown by MOCVD on semi-insulating SiC substrates. The devices exhibited current density of 1300 mA/mm, peak dc extrinsic transconductance of 275 mS/mm, unity current gain cutoff () of 65 GHz, and maximum frequency of oscillation (max) of 110 GHz. Saturated output power at 20 GHz was 6.4 W/mm with 16% power added efficiency (PAE), and output power at 1-dB compression at 30 GHz was 4.0 W/mm with 20% PAE. This is the highest power reported for 0.25-m gate-length devices at 20 GHz, and the 30 GHz results represent the highest frequency power data published to date on GaN-based devices.

Research paper thumbnail of The 1.6-kV AlGaN/GaN HFETs

IEEE Electron Device Letters, 2006

The breakdown voltages in unpassivated nonfieldplated AlGaN/GaN HFETs on sapphire substrates were... more The breakdown voltages in unpassivated nonfieldplated AlGaN/GaN HFETs on sapphire substrates were studied. These studies reveal that the breakdown is limited by the surface flashover rather than by the AlGaN/GaN channel. After elimination of the surface flashover in air, the breakdown voltage scaled linearly with the gate-drain spacing reaching 1.6 kV at 20 µm. The corresponding static ON-resistance was as low as 3.4 mΩ • cm 2. This translates to a power device figure-of-merit V 2 BR /R ON = 7.5 × 10 8 V 2 • Ω −1 cm −2 , which, to date, is among the best reported values for an AlGaN/GaN HFET.

Research paper thumbnail of Silicon Dioxide-Encapsulated High-Voltage AlGaN/GaN HFETs for Power-Switching Applications

IEEE Electron Device Letters, 2007

Research paper thumbnail of DC and microwave performance of high-current AlGaN/GaN heterostructure field effect transistors grown on p-type SiC substrates

IEEE Electron Device Letters, 1998

Research paper thumbnail of AlGaN/GaN HEMTs on SiC with f/sub T/ of over 120 GHz

IEEE Electron Device Letters, 2002

AlGaN/GaN high electron mobility transistors (HEMTs) grown on semi-insulating SiC substrates with... more AlGaN/GaN high electron mobility transistors (HEMTs) grown on semi-insulating SiC substrates with a 0.12 m gate length have been fabricated. These 0.12m gate-length devices exhibited maximum drain current density as high as 1.23 A/mm and peak extrinsic transconductance of 314 mS/mm. The threshold voltage was 5.2 V. A unity current gain cutoff frequency () of 121 GHz and maximum frequency of oscillation (max) of 162 GHz were measured on these devices. These and max values are the highest ever reported values for GaN-based HEMTs.

Research paper thumbnail of Low-loss high power RF switching using multifinger AlGaN/GaN MOSHFETs

IEEE Electron Device Letters, 2002

Research paper thumbnail of AlGaN-GaN HEMTs on SiC with CW power performance of >4 W/mm and 23% PAE at 35 GHz

IEEE Electron Device Letters, 2003

In this letter, continuous wave-band power performance of AlGaN-GaN high electron-mobility transi... more In this letter, continuous wave-band power performance of AlGaN-GaN high electron-mobility transistors grown on semi-insulating SiC substrates are reported. The devices, with gate lengths of 0.25 m, exhibited maximum drain current density of 1.1 A/mm and peak extrinsic transconductance of 285 mS/mm. At 35 GHz, an output power density of 4.13 W/mm with 23% of power-added efficiency (PAE) and 7.54 dB of linear gain were achieved at a drain bias of 30 V. These power results represent the best power density, PAE, and gain combination reported at this frequency. The drain bias dependence of the-band power performance of these devices is also presented. Index Terms-AlGaN, GaN, microwave power high electron mobility transistors (HEMTs).

Research paper thumbnail of Thermal management of AlGaN-GaN HFETs on sapphire using flip-chip bonding with epoxy underfill

IEEE Electron Device Letters, 2003