Haecheon Kim

2.9 V operation GaAs power MESFET with 31.5-dBm output power and 64% power-added efficiency

A state-of-the-art GaAs power MESFET operating at a drain bias of 2.9 V has been developed using the high-low doped channel structure grown by molecular beam epitaxy. The device has 0.6 /spl mu/m gate length and 16 mm gate width. The power performance tested at a 2.9 V drain bias and 900 MHz operation frequency was output power of 31.5 dBm with 11.5 dB gain and 64% power-added efficiency. >

A 68% PAE, GaAs power MESFET operating at 2.3 V drain bias for low distortion power applications

A high-efficient GaAs power metal semiconductor field effect transistor operating at a drain voltage of 2.3 V has been developed for low distortion power applications. The device has been fabricated on an epitaxial layer with a high-low doped structure grown by molecular beam epitaxy. The MESFET with a gate length of 0.8 /spl mu/m and a total gate width of 21.16 mm showed a maximum drain current of 5.9 A at V/sub gs/=0.5 V, a knee voltage of 1.0 V and a gate-to-drain breakdown voltage of 28 V. The MESFET tested at a 2.3 V drain bias and a 900 MHz operation frequency displayed the best power-added efficiency of 68% with an output power of 31.3 dBm. The associate power gain at 20 dBm input power and the linear gain were 11.3 dB and 16.0 dB, respectively. The power characteristics of the device operating under a bias of 2 V exhibit power-added efficiency of 67% and output power of 30.1 dBm at an input power of 20 dBm. Two tone test measured at 900.00 MHz and 900.03 MHz shows that 3rd-order intermodulation and power-added efficiency at an output power of 27 dBm were -30.6 dBc and 36%, respectively, which are good for CDMA digital applications. A third-order intercept point and a linearity figure-of-merit were measured to be 49.5 dBm and 53.8, respectively.

Single supply, high linearity, high efficient PHEMT power devices and amplifier for 2 GHz & 5 GHz WLAN applications

A single supply, high linearity, high efficient power devices and amplifier MMIC is implemented utilizing high performance of quasi-enhanced power PHEMT technology. The PHEMT power device features Vth= ¿0.65 V, Vbdg=26 V, Imax=144 mA/mm at Vgs=0.2 V, Gm=340 mS/mm. When matched on-wafer compromise between power and efficiency, the OIP3 at peak IP3 is 40.5 dBm for 2 GHz and 37.0 dBm for 5.8 GHz, respectively. The power amplifier achieves at 5.8 GHz Pout=27 dBm with associated PAE=45% at 5 V under Vgs=0 V, GL=14.5 dB, OIP3=37.5 dBm.

Experimental Study on Isolation Characteristics Between Adjacent Microstrip Lines Employing Periodically Perforated Ground Metal for Application to Highly Integrated GaAs MMICs

Using a periodically perforated ground metal (PPGM) on GaAs monolithic microwave integrated circuit (MMIC), a microstrip line structure with a high isolation characteristic between lines was developed. The high isolation characteristic was originated from a resonance between adjacent microstrip lines employing PPGM. According to experimental results, a much better isolation characteristic was observed from the adjacent microstrip lines employing PPGM compared with conventional microstrip lines, and the frequency range for high isolation was easily controlled by changing the PPGM structure. Above results indicate that microstrip lines employing PPGM are very useful for application to compact signal/bias lines of highly integrated MMIC requiring a high isolation characteristics between lines.

Pd/Ge/Ti/Au ohmic contact to AlGaAs/InGaAs pseudomorphic high electron mobility transistor with an undoped cap layer

The Pd/Ge/Ti/Au ohmic contact to AlGaAs/InGaAs pseudomorphic high electron mobility transistor was investigated with the etch depth of an undoped GaAs/AlGaAs cap layer. The contact resistivity decreases from 9.5×10−5 to 2.3×10−6 Ω cm2 when the contacts were formed on a n-Al0.23Ga0.77As layer by removing the undoped cap layer. X-ray diffraction results show that the good ohmic contact is due to the formation of Au2Al as well as β-AuGa. Both compounds play a role to create group-III vacancies, followed by the incorporation of Ge into group-III vacancies, namely, creation of free electron below the contact. This results in the considerable elimination of contact resistivity by lowering the effective tunneling barrier.

A 15-GHz 7-channel SiGe:C PLL for 60-GHz WPAN Application

In this paper, we present the design of 15-GHz frequency synthesizer for 60-GHz WPAN. The PLL generates 7 channels of output signals with 250 MHz step by using the highspeed programmable divider operating up to 10 GHz. A double cross-coupled LC VCO is used for achieving higher oscillation frequency and shows about 20 % tuning range. The PLL represents phase noise of -88 dBc/Hz at 1 MHz offset from 15.75 GHz and consumes 115 mA at 2.5 V supply voltage. The PLL occupies 0.7 times 0.8 mm2 area and is fabricated using 0.25 mum SiGe:C BiCMOS process technology.

A Ku-band T-shaped gate GaAs power MESFET with high breakdown voltage for satellite communications

/sup G/aAs power MESFETs with 0.5-/spl mu/m T-shaped gate for Ku-band power applications have been developed using a new self-aligned and optical lithography. It displays a maximum current density of 350 mA/mm, an uniform transconductance of 150 mS/mm and a high gate-to-drain breakdown voltage of 35 V. Both the high breakdown voltage and the uniform transconductance were achieved by the new MESFET design incorporating an undoped GaAs cap and a thick lightly doped active layers. The breakdown voltage is the highest one among the values reported on the power devices. The device exhibits 0.61 W/mm power density and 47% power added efficiency with 9.0 dB associated gain at a drain bias of 12 V and an operation frequency of 12 GHz.

A 45-to-60-GHz Two-Band SiGe: C VCO for Millimeter-Wave Applications

A 45 - 60-GHz two-band double cross-coupled differential VCO is designed and fabricated using 0.25 mum SiG:C BiCMOS process technology whose fmax is greater than 200 GHz. The VCO provides tuning ranges of 44.9 - 48.9 GHz when its bias current is 13 mA and of 58 - 60.4 GHz when a bias current of 7 mA draws into the VCO. The phase noises of the VCO are measured as - 99 dBc/Hz from 48.86 GHz and - 93 dBc/Hz from 60.32 GHz, at 10 MHz offset, respectively. The VCO shows moderate FOMs of 156 dBc at 60.32 GHz and 158 dBc at 48.86 GHz.

Interface-controlled gate of GaAs metal–semiconductor field-effect transistor

A two-step passivation using sulfidation and hydrogenation has been reported to improve the gate leakage current and breakdown voltage of the GaAs metal–semiconductor field-effect transistor (MESFET). The combination of S passivation and interfacial hydrogenation was applied to the gate line in the MESFET; leakage current was reduced over an order and breakdown voltage was improved to a maximum level of 14 V from 10 V. It was revealed that the improvement of device properties after this two-step treatment resulted from the suppression of defective states such as oxides and excess As at the interface of the gate junction. The evolution of their bonding states through the treatment was found to have a close relationship with the device parameters.

Microwave Low-Noise Performance of

Microwave low-noise performance AlGaN/GaN HEMT on a SiC substrate with a wide head double-deck T-shaped gate has been reported. The HEMTs with gatelength (L_g) of 0.17 μm and source-drain spacing (L_sd) of 3.5 μm exhibited a maximum extrinsic transconductance of 360 mS/mm, a current gain cutoff frequency (f_T) of 50 GHz, a maximum oscillation frequency (f_max) of 149 GHz, and three-terminal breakdown voltage of 113 V. The device exhibited a minimum noise figure (NF_min) of 0.50 and 0.84 dB at 10 and 18 GHz, respectively, when biased at V_ds = 5 V and I_ds = 140 mA/mm, which is the lowest noise characteristics ever reported for the GaN-based T-shaped gate HEMTs with gate length larger than 0.1 μm. This excellent noise performance is attributed to the reduction of the gate resistance resulting from a wide head T-shaped gate and the improved device characteristics.