Hyung-Moo Park

Ultra low noise characteristics of AlGaAs/InGaAs/GaAs pseudomorphic HEMT's with wide head T-shaped gate

The fully passivated low noise AlGaAs/InGaAs/GaAs pseudomorphic (PM) HEMT with 0.13 /spl mu/m T-shaped gate was fabricated using dose split electron beam lithography method (DSM). This device exhibited low noise figures of 0.31 and 0.45 dB at 12 and 18 GHz, respectively. These noise figures are the lowest value ever reported for the GaAs based HEMTs. These results are attributed to the extremely low gate resistance which results from wide head T-shaped gate having the higher ratio more than 10 of gate head length to gate footprint.

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 GaAs power amplifier for 3.3 V CDMA/AMPS dual-mode cellular phones

For CDMA/AMPS dual-mode cellular phones, a power amplifier operating at 3.3 V has been developed for the first time. It consists of linear GaAs power MESFETs and an output matching circuit which reduces the second and the third harmonics. The amplifier shows an output power of 31.5 dBm and a power-added efficiency of 61% for the AMPS mode. The third-order intermodulation distortion and the fifth-order one are measured to be -32 dBc and -45 dBc at an output power of 26 dBm for the CDMA mode.

A low noise amplifier for a multi-band and multi-mode handset

Using a low noise active balun and a push-pull active matching circuit, a wideband low noise amplifier MMIC is designed and fabricated. For the frequency up to 3 GHz, output VSWR is less than 1.3 and the output power handling capability of 9.4 dB is enhanced compared with conventional active matching circuit.

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.

Optical device module packages for subscriber incorporating passive alignment techniques

Compact optical module packages for use as 156 Mbps optical interfaces have been developed by incorporating passive alignment techniques. In this approach, a laser chip and a fiber are aligned on a V-grooved silicon substrate by flip-chip bonding. The silicon substrates have been fabricated by conventional silicon processing and micro-machining technologies. A new feature of our fabrication technique is to implement a self-alignment principle for the formation of V-grooves and solder bumps, which eliminates a registration error from the individual process. The laser diode and photo diode submodules, assembled on silicon substrates, exhibited 4-6% and about 80% coupling efficiencies, respectively. The fabricated proto-type transmitter and receiver module packages have a very compact size of 5 cc each and showed adequate performance satisfying the requirement for optical subscriber transmitter and receiver modules.

Molecular beam epitaxy growth of indium-rich InxGa1 − xAsInyAl1 − yAs/InP structures towards high channel conductivity for a high electron mobility transistor using a linearly graded buffer layer

InxGa1 − xAsInyAl1 − yAs heterostructure with both high electron mobility and high carrier concentration has been fabricated on InP substrate by molecular beam epitaxy. The measured electron mobilities were 11 491 cm2/V · s at 300 K and 53 316 cm2/V · s at 77 K for two-dimensional electron gas concentrations of 4.7 × 1012 and 3.5 × 1012 cm−2, respectively. The high electron mobility and concentration resulted from the dislocation-free, relatively thick (200 A), and high indium content (80%) channel layer. The high-quality InxGa1 − xAs channel layer was successfully grown at a growth temperature of 520°C after introducing a linearly graded InyAl1 − yAs buffer structure grown at a reduced growth temperature of 420°C. The cross-sectional transmission electron microscopy observation revealed that the dislocations generated due to a large lattice mismatch between InyAl1 − yAs and InP substrate were locked up in the middle of the graded buffer layer. We believe that we have achieved to date for this materials system the highest room-temperature conductivity (mobility times carrier concentration) of 5.4 × 1016/V · s.

Reliability considerations of laser diodes for optical communication system application

The purpose of this paper is to propose a reliability parameter of laser diodes for optical communication system applications. Based on the alarm function in optical communication systems, we have developed a reliability parameter; /spl rho//sub a/(=/spl eta//sub a///spl eta//sub 0/.Ith/sub a//Ith/sub 0/)/spl ges/1.5, which is more applicable to estimate reliability projections and to design LD modules for optical communication systems.

The wideband characteristics of plate antenna with elliptical cross section

In this paper, a plate antenna with elliptical cross section and ellipticity ratio is studied. The return loss of the proposed antenna and conventional antennas is investigated using the simulation package CST MW Studio ver. 3.2 and fabricated antennas. The effects of ellipticity ratio on the radiation pattern and reflection coefficients are described. The given structure can handle the average power of several hundreds of watts. The simulated results of this antenna are obtained for various values of the ellipticity ratio of elliptical cross section loaded at the input port

2.3 V operation GaAs power MESFET with 68% power-added efficiency

A state-of-the-art GaAs power MESFET operating at a drain bias of 2.3 V has been developed using the low-high doped channel structure. The device has 0.8-/spl mu/m gate length and 21-mm gate width. The power performance tested at a 2.3 V drain bias under 900 MHz operation frequency was output power of 31.3-dBm with 11.3-dB gain and 69-percent power-added efficiency. A third-order intercept point was evaluated to be 50.7-dBm. A Linearity Figure-of-Merit of 55.6 was recorded for 21-mm-wide FET.