Jeon-Wook Yang

A new extraction method to determine bias-dependent source series resistance in GaAs FET's

A new method is proposed to determine bias-dependent source resistances for GaAs field-effect transistors (FETs). This method, which is a cold-FET measurement technique, utilizes the relations between the real part of the two-port impedances transformed from the measured S-parameters and their algebraic derivatives. It is based on the fact that the algebraic derivatives of the two-port resistances result in the simple form at the normal cold-FET condition. A bias-independent gate resistance is extracted at the pinched-off cold-FET condition to fulfill necessary and sufficient conditions in extraction. The proposed method is a direct measurement because only algebraic calculation is required, and it is general enough to need only one assumption of the laterally symmetric channel-doping profile. The deleterious results of dispersion (frequency dependence) and negative value in source resistances at the pinched-off cold-FET condition are explained by the effects of the leakage current and the on-wafer pad parasitics, respectively. The problem of deviation of /spl alpha//sub 21/ and /spl alpha//sub 12/ from 0.5 at the normal cold-FET condition is also resolved by deembedding the on-wafer pad parasitics. This method allows one to extract bias-dependent source resistances for GaAs FETs.

1.5 V ultrawide-band GaAs monolithic amplifier for portable wireless LAN and satellite communication applications

A 1.5 V operating GaAs 2/spl sim/9 GHz ultrawide-band MMIC amplifier for portable wireless LAN, microwave link and satellite communication applications has been developed. This amplifier has 16/spl plusmn/1 dB gain and more than 10 dB input and output return loss in the 2/spl sim/9 GHz frequency range with 118 mA operating current. Measured 1-dB compression power is 13 dBm at 0 dBm input power and minimum noise figure is 4.8 dB. When operated at 3 V and 128 mA, this amplifier has up to 18/spl plusmn/1 dB gain, 18 dBm 1-dB compression power, more than 10 dB return loss and 4.9 dB minimum noise figure.

A 3.3 V front-end receiver GaAs MMIC for the digital/analog dual-mode hand-held phones

A front-end receiver MMIC for 3.3 V-operating CDMA/AMPS dual-mode hand held phone has been developed using a GaAs MESFET process. The developed MMIC, chip size of which is 1.9/spl times/3.9 mm/sup 2/ shows noise figure of 2.8 dB, power gain of 35/25 dB at the nominal current consumption of 22.5/16.1 mA in CDMA/AMPS modes, respectively.

Effect of Al 2 O 3 Surface Passivation by Thermal Oxidation of Aluminum for AlGaN/GaN Structure

Surface passivation of AlGaN/GaN heterojunction structure was examined through the thermal oxidation of evaporated Al. The Al-oxide passivation increased channel conductance of two dimensional electron gas (2DEG) on the AlGaN/GaN interface. The sheet resistance of 463 ohm/ for 2DEG channel before passivation was decreased to 417 ohm/ after passivation. The oxidation of Al induces tensile stress to the AlGaN/GaN structure and the stress seemed to enhance the sheet carrier density of the 2DEG channel. In addition, the films formed by thermal oxidation of Al suppressed thermal deterioration by the high temperature annealing.

Comparison of Electrical Characteristics of SiGe pMOSFETs Formed on Bulk-Si and PD-SOI

This paper has demonstrated the electrical properties of SiGe pMOSFETs fabricated on both bulk-Si and PD SOI substrates. Two principal merits, the mobility increase in strained-SiGe channel and the parasitic capacitance reduction of SOI isolation, resulted in improvements in device performance. It was observed that the SiGe PD SOI could alleviate the floating body effect, and consequently DIBL was as low as 10 mV/V. The cut-off frequency of device fabricated on PD SOI substrate was roughly doubled in comparison with SiGe bulk: from 6.7 GHz to 11.3 GHz. These experimental result suggests that the SiGe PD SOI pMOSFET is a promising option to drive CMOS to enhance performance with its increased operation frequency for high speed and low noise applications.

RTA Effect on Transport Characteristics in Al 0.25 Ga 0.75 As/In 0.2 Ga 0.8 As pHEMT Epitaxial Structures Grown by Molecular Beam Epitaxy

We have investigated structures for pseudomorphic high electron mobility transistor(pHEMT), which were grown by molecular beam epitaxy(MBE) and consequently annealed by rapid thermal anneal(RTA), using Hall measurement, photoluminescence, and transmission electron microscopy (TEM). According to intensity and full-width at half maximum maintained stable at the same energy level, the quantized energy level in quantum wells was independent of the RTA conditions. However, the Hall mobility was decreased from after heat treatment respectively at . The heat treatment which is indispensable during the fabrication procedure would cause catastrophic degradation in electrical transport properties. TEM observation revealed atomically non-uniform interfaces, but no dislocations were generated or propagated. From theoretical consideration about the mobility changes owing to inter-diffusion, the degraded mobility could be directly correlated to the interface scattering as long as samples were annealed below lot 1 min.

Determination of Bias-Dependent Source Resistances in GaAs MESFETs under Cold-FET Condition

A new method to determine bias-dependent source resistances for GaAs MESFETs is introduced. The method is a combination of the cold- and pinched-FET measurement techniques based on the real parts of the two-port impedances and their derivatives. The proposed method offers a unique extraction procedure only assuming that the channel doping profile is symmetric. The deleterious problems of negative source resistances in the pinched-FET condition and the deviation of ¿21 and ¿12 from 0.5 in the cold-FET condition are solved by deembedding the on-wafer pad parasitics. The usefulness of the method has been demonstrated by extracting source resistances for two types of MESFETs. The results were self-consistent enough to confirm the validity of this method.

Ion-implanted WN 0.25 /spl mu/m gate MESFET fabricated using i-line photolithography for application to MMIC and digital IC

Straightforward WN 0.25 /spl mu/m gate MESFET process based on direct ion-implantation and i-line photolithography with double exposure process has produced high performance MESFETs. The maximum transconductance of 600 mS/mm and the k-factor of 450 ms/Vmm were obtained. As high as 65 GHz of cut-off frequency has been realized without any deembedding of parasitic effects. The MESFET shows the minimum noise figure of 0.87 dB and the associated gain of 9.97 dB at 12 GHz.