TY - CHAP A1 - Schott, Matthias A1 - Kuhnert, Holger A1 - Lenk, Friedrich A1 - Hilsenbeck, Jochen A1 - Würfl, Joachim A1 - Heinrich, Wolfgang T1 - 38 GHz push-push GaAs-HBT MMIC oscillator T2 - 2002 IEEE MTT-S International Microwave Symposium digest, June 2 - 7, 2002, Washington State Convention & Trade Center, Seattle, Washington, vol. 2 N2 - Two differential coplanar MMIC HBT oscillators are presented, a fixed frequency and a VCO version. They provide single-ended output at the second harmonic at 38 GHz as well as differential output at 19 GHz. The oscillators show excellent phase noise performance, the fixed-frequency type reaches -95 dBc/Hz at the fundamental frequency and -89 dBc/Hz at the second harmonic, at 100 kHz offset. Y1 - 2002 SN - 0-7803-7239-5 U6 - https://doi.org/10.1109/MWSYM.2002.1011761 SP - 839 EP - 842 PB - IEEE Service Center CY - Piscataway, NJ ER - TY - CHAP A1 - Lenk, Friedrich A1 - Schott, Matthias A1 - Hilsenbeck, Jochen A1 - Würfl, Joachim A1 - Heinrich, Wolfgang T1 - Low phase-noise monolithic GaInP/GaAs-HBT VCO for 77 GHz T2 - 2003 IEEE MTT-S International Microwave Symposium digest, June 8 - 13, 2003, Pennsylvania Convention Center, Philadelphia, Pennsylvania, vol. 2 N2 - Coplanar W-band push-push VCO MMICs using GaInP/GaAs HBTs are presented. One circuit operates at 77 GHz with phase noise of -92 dBc/Hz at 1 MHz offset. To our knowledge this is the first fully monolithic W-band VCO with phase noise better than -90 dBc/Hz. A second version with two varactor diodes yields an almost threefold relative tuning bandwidth. Y1 - 2003 SN - 0-7803-7695-1 U6 - https://doi.org/10.1109/MWSYM.2003.1212515 SP - 903 EP - 906 PB - IEEE Service Center CY - Piscataway, NJ ER - TY - GEN A1 - Sonia, G. A1 - Richter, E. A1 - Brunner, F. A1 - Denker, A. A1 - Lossy, R. A1 - Mai, M. A1 - Lenk, Friedrich A1 - Bundesmann, J. A1 - Pensl, G. A1 - Schmidt, J. A1 - Zeimer, U. A1 - Wang, L. A1 - Baskar, K. A1 - Weyers, M. A1 - Würfl, Joachim A1 - Tränkle, Günther T1 - 2 MeV ion irradiation effects on AlGaN/GaN HFET devices T2 - Solid-State Electronics N2 - AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with 2 MeV protons, carbon, oxygen, iron and krypton ions with fluences ranging from 1 × 109 cm−2 to 1 × 1013 cm−2. DC, pulsed I–V characteristics, loadpull and S-parameters of the AlGaN HFET devices were measured before and after irradiation. In parallel, a thick GaN reference layer was also irradiated with the same ions and was characterized by X-ray diffraction, photoluminescence, Hall measurements before and after irradiation. Small changes in the device performance were observed after irradiation with carbon and oxygen at a fluence of 5 × 1010 cm−2. Remarkable changes in device characteristics were seen at a fluence of 1 × 1012 cm−2 for carbon, oxygen, iron and krypton irradiation. Similarly, remarkable changes were also observed in the GaN layer for irradiations with fluence of 1 × 1012 cm−2. The results found on devices and on the GaN layer were compared and correlated. Y1 - 2008 UR - http://www.sciencedirect.com/science/article/pii/S0038110108000671 SN - 0038-1101 VL - 52 IS - 7 SP - 1011 EP - 1017 ER - TY - GEN A1 - Gnanapragasam, S. A1 - Richter, E. A1 - Brunner, F. A1 - Denker, A. A1 - Lossy, R. A1 - Mai, M. A1 - Lenk, Friedrich A1 - Opitz-Coutureau, J. A1 - Pensl, G. A1 - Schmidt, J. A1 - Zeimer, U. A1 - Wang, L. A1 - Krishnan, B. A1 - Weyers, M. A1 - Würfl, Joachim A1 - Tränkle, Günther T1 - Irradiation effects on AlGaN HFET devices and GaN layers T2 - Journal of Materials Science: Materials in Electronics N2 - AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with protons as well as carbon, oxygen, iron and krypton ions of high (68 and 120 MeV) and low (2 MeV) energy with fluences in the range from 1x107 to 1x1013 cm-2. High energy irradiation with protons, carbon and oxygen produced no degradation in devices while krypton irradiation at the fluence of 1x1010 cm-2 resulted in a small reduction of 2% in the transconductance. Similarly, for GaN samples irradiated with protons, carbon and oxygen at high energy no changes were seen by XRD, PL and Hall effect, while changes in lattice constant and a reduction in PL intensity were observed after irradiation with high energy krypton. Low energy irradiation with carbon and oxygen at a fluence of 5x1010 cm-2 results in small change in the device performance while remarkable changes in device characteristics are seen at a fluence of 1x1012 cm-2 for carbon, oxygen, iron and krypton irradiation. Similarly changes are also observed by XRD, PL and Hall effect for the thick GaN layer irradiated at the fluence of 1x1012 cm-2. The device results and GaN layer properties are strongly correlated. Y1 - 2008 U6 - https://doi.org/10.1007/s10854-008-9589-1 SN - 1573-482X VL - 19 IS - 1 SP - 64 EP - 67 ER - TY - GEN A1 - Sonia, G. A1 - Richter, E. A1 - Brunner, F. A1 - Denker, A. A1 - Lossy, R. A1 - Lenk, Friedrich A1 - Opitz-Coutureau, J. A1 - Mai, M. A1 - Schmidt, J. A1 - Zeimer, U. A1 - Wang, L. A1 - Baskar, K. A1 - Weyers, M. A1 - Würfl, Joachim A1 - Tränkle, Günther T1 - High energy irradiation effects on AlGaN/GaN HFET devices T2 - Semiconductor Science and Technology N2 - The effect of proton, carbon, oxygen and krypton irradiation on AlGaN HFET devices has been studied. Irradiation was performed at 68 and 120 MeV with fluences in the range from 1 × 10^7 to 1 × 10^13 cm2 . Before and after irradiation, dc and pulsed I – V characteristics, loadpull and S -parameters of the AlGaN HFET devices were measured. A thick GaN reference layer was characterized by x-ray diffraction, photoluminescence and Hall measurements before and after irradiation. Proton, carbon and oxygen irradiation show no degradation in devices while krypton irradiation shows a small change at a fluence of 1 × 10 10 cm2 in the device characteristics. The device results are correlated with the thick GaN results. Y1 - 2007 U6 - https://doi.org/10.1088/0268-1242/22/11/007 SN - 0268-1242 VL - 22 IS - 11 SP - 1220 EP - 1224 ER - TY - CHAP A1 - Hilsenbeck, Jochen A1 - Brunner, F. A1 - Lenk, Friedrich A1 - Würfl, Joachim T1 - Fabrication and Electrical Performance of Oscillators in GaAs/GaInP-HBT MMIC Technology up to 40 GHz T2 - 29th International Symposium on Compound Semiconductors (ISCS), Lausanne/Switzerland, 2002 Y1 - 2002 SN - 0-7503-0942-3 SN - 978-07503-0942-4 SP - 239 EP - 242 PB - Institute of Physics Publ. CY - Bristol [u.a.] ER - TY - GEN A1 - Yazdani, Hossein A1 - Zervos, Christos A1 - Beleniotis, Petros A1 - Brusaterra, Enrico A1 - Hilt, Oliver A1 - Rudolph, Matthias A1 - Würfl, Joachim T1 - Importance of Scaling in RF GaN HEMTs for Reduction of Surface Traps‐Induced Drain Lag T2 - Physica Status Solidi (a) N2 - Drain lag is a well‐known phenomenon that leads to radio frequency performance degradation in AlGaN/GaN high‐electron‐mobility transistors. Herein, it is demonstrated that a reduction of the gate‐to‐drain distance (Lgd) from 2.0 to 0.5 μm results in 7% reduction in the current collapse. This improvement is attributed to a decrease in surface trapping, which, in this case, is found to have a greater impact on current collapse than relatively slow traps in the buffer layer. To support this argument, TCAD simulations are conducted. Load‐pull analysis confirms that scaling the devices to Lgd = 0.5 μm provides 15% better output power density at 10 GHz than Lgd = 2.0 μm. Additionally, a new passivation layer for reduced surface traps exhibits a 20 to 30% higher output power density and at least a 10% improvement in power‐added efficiency at 20 GHz on a nominally identical GaN‐on‐semi‐insulating SiC epi‐wafer. Y1 - 2024 U6 - https://doi.org/10.1002/pssa.202300885 SN - 1862-6300 SP - 1 EP - 8 PB - Wiley ER - TY - GEN A1 - Yazdani, Hossein A1 - Beleniotis, Petros A1 - Brunner, Frank A1 - Ostermay, Ina A1 - Würfl, Joachim A1 - Rudolph, Matthias A1 - Heinrich, Wolfgang A1 - Hilt, Oliver T1 - K/Ka-Band-GaN-High-Electron-Mobility Transistors Technology with 700 mS mm-1 Extrinsic Transconductance T2 - Physica Status Solidi Y1 - 2024 U6 - https://doi.org/10.1002/pssa.202400592 ER -