Browsing by Author "Wuerfl, Joachim"

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Bandwidth Improvement of MMIC Single-Pole-Double-Throw Passive HEMT Switches with Radial Stubs in Impedance-Transformation Networks
(2020-02-01)
Tsao, Yi-Fan
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Wuerfl, Joachim
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Hsu, Heng-Tung
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國際半導體學院
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International College of Semiconductor Technology
In this paper, we propose a new configuration for improving the isolation bandwidth of MMIC single-pole-double-throw (SPDT) passive high-electron-mobility transistor (HEMT) switches operating at millimeter frequency range. While the conventional configuration adopted open-stub loading for compensation of the off-state capacitance, radial stubs were introduced in our approach to improve the operational bandwidth of the SPDT switch. Implemented in 0.15 m GaAs pHEMT technology, the proposed configuration exhibited a measured insertion loss of less than 2.5 dB with better than 30 dB isolation level over the frequency range from 33 GHz to 44 GHz. In terms of the bandwidth of operation, the proposed configuration achieved a fractional bandwidth of 28.5% compared to that of 12.3% for the conventional approach. Such superior bandwidth performance is mainly attributed to the less frequency dependent nature of the radial stubs.
Performance Enhancement of Flip-Chip Packaged AlGaN/GaN HEMTs by Strain Engineering Design
(2016-10)
Tsai, Szu-Ping
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Hsu, Heng-Tung
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Wuerfl, Joachim
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Chang, Edward Yi
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材料科學與工程學系
The piezoelectric polarization of the AlGaN/GaN high-electron-mobility transistors (HEMTs) is strongly related to the strain state in the active area. Therefore, understanding the strain behavior inside the channel is crucial to the device electrical performance improvement of devices. This paper, for the first time, reveals the potential of optimizing flip-chip structures with active-region bumps to modulate the strain state of the AlGaN/GaN HEMT for enhancing the piezoelectric effect. The thermo-mechanical strain is observed to be affected by the physical dimensions and the material properties of the package. Thus, incorporating device strain engineering into packaging design will be very important for GaN devices due to their strong piezoelectric effects.
WSiN Cap Layer for Improvement of Ohmic Contact Morphology in AlGaN/GaN High Electron Mobility Transistors
(2009-11-01)
Lu, Chung Yu
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Hilt, Oliver
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Lossy, Richard
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Chaturvedi, Nidhi
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John, Wilfred
A new technique using WSiN film as a protective cap layer of the internal ohmic metallization scheme and the GaN surface was developed to improve the surface morphology of the contact of AlGaN/GaN high electron mobility transistors (HEMTs) After annealing, this layer was selectively removed by patterning and dry etching. Metal contact surfaces covered with WSiN preserved a good surface morphology and edge definition. Moreover, the devices have a saturation current of 1 A/mm and a maximum transconductance of 235 mS/mm When biased at 30 V, the output power density is 5 8 W/mm at 2 GHz These results indicate a damage-free process for the smooth ohmic contacts formation (C) 2009 The Japan Society of Applied Physics