이재승 교수

This work reports on SiGe HBTs with f/sub T/ of 350 GHz. This is the highest reported f/sub T/ for any Si-based transistor as well as any bipolar transistor. Associated f/sub max/ is 170 GHz, and BV/sub CEO/ and BV/sub CBO/ are measured to be 1.4 V and 5.0 V, respectively. Also achieved was the simultaneous optimization of f/sub T/ and f/sub max/ resulting in 270 GHz and 260 GHz, with BV/sub CEO/ and BV/sub CBO/ of 1.6 V and 5.5 V, respectively. The dependence of device performance on bias condi

The relatively less exploited terahertz band possesses great potential for a variety of important applications, including communication applications that would benefit from the enormous bandwidth within the terahertz spectrum. This paper overviews an approach toward terahertz applications based on SiGe heterojunction bipolar transistor (HBT) technology, focusing on broad-band communication applications. The design, characteristics, and reliability of SiGe HBTs exhibiting record f/sub T/ of 375 G

Thermal resistance has been measured for high speed SiGe HBTs with various emitter widths and lengths. The smaller devices exhibited higher thermal resistance values, but eventually resulted in lower junction temperature rise for a given power density. A physical model has been developed which showed good agreement with the measurements. The model indicates that the thermal resistance depends strongly on the deep trench geometry. The thermal resistance is also anticipated to increase with the ex

Scaling has been the principal driving force behind the successful technology innovations of the past half-century. This paper investigates the impacts of scaling on SiGe heterojunction bipolar transistors (HBTs), which have recently emerged as a strong contender for RF and mixed-signal applications. The impacts of scaling on key performance metrics such as speed and noise are explored, and both theory and data show that scaling, both vertical and lateral, has mostly beneficial effects on these

The current level in the modern high-speed SiGe heterojunction bipolar transistors (HBTs) continues to increase for operation speed enhancement, but the resultant self-heating and elevated junction temperature emerge as a growing concern for device reliability as well as performance. To address such thermal issues, the optimization of SiGe HBT structures to achieve simultaneous improvements in thermal and electrical performance is carried out in this study. As a foundation for the study, an R/su

The effect of the structural variation of device on its thermal resistance was investigated for trench-isolated bipolar transistors. Devices with various number of emitter segments and inter-segment spacings and several different trench-to-emitter distances were fabricated and the thermal resistance was measured/compared. An analytical thermal model was also developed and provided a good prediction on the structural dependence of the thermal resistance, exhibiting a good agreement with the measu

A double mesa-structure Si/SiGe heterojunction bipolar transistor (HBT) and novel micromachined lumped passive components have been developed and successfully applied to the fabrication of X- and Ku-band monolithic amplifiers. The fabricated 5/spl times/5 /spl mu/m/sup 2/ emitter-size Si/SiGe HBT exhibited a DC-current gain /spl beta/ of 109, and f/sub T/ and f/sub max/ of 28 and 52 GHz, respectively. Micromachined spiral inductors demonstrated resonance frequency of 20 GHz up to 4 nH, which is

Millimeter-wave applications are gaining growing interest in recent times. To meet the challenges for such applications, SiGe HBTs, with simultaneously optimized f/sub T/ and f/sub max/ of >300 GHz, are developed. To the author's knowledge, this is the first report of f/sub T/ and f/sub max/ both exceeding 300 GHz for any Si-based transistor. BV/sub CEO/ and BV/sub CBO/ are 1.6 V and 5.5 V, respectively, with peak current gain of 660. Noise measurement shows F/sub min/ of 0.45 dB and 1.4 dB at 1

As device scaling for higher performance bipolar transistors continues, the operation current density increases as well. To investigate the reliability impact of the increased operation current density on Si-based bipolar transistors, an accelerated-current wafer-level stress was conducted on 120-GHz SiGe heterojunction bipolar transistors (HBTs), with stress current density up to as high as J/sub C/=34 mA//spl mu/m/sup 2/. With a novel projection technique based on accelerated-current stress, a

A 260‐GHz amplifier in a SiGe heterojunction bipolar transistor (HBT) technology is reported. It is based on three‐stage differential cascode topology and adopts a passive shunt transistor pair at the output of each amplifying stage to relax instability caused by parasitic base inductance of amplifying transistor pair. The instability of the amplifier can be mitigated by tuning the base bias voltage of the shunt transistor pair. Peak gain of the amplifier was measured as 15 dB at 260 GHz. DC pow

Fabrication and characterization of monolithically integrated SiGe-Si PIN-HBT transimpedance photoreceivers are reported. SiGe-Si technology has been developed leading to SiGe-Si HBT's with f/sub T/=23 GHz and f/sub max/=34 GHz, and to PIN photodiodes with responsivity of 0.3 A/W at /spl lambda/=850 nm and bandwidth of 450 MHz. SiGe-Si HBT transimpedance amplifiers showed transimpedance gain of 52.2 dB./spl Omega/ and bandwidth of 1.6 GHz, and the photoreceivers exhibited the bandwidth of 460 MH

The current characteristics of SiGe heterojunction bipolar transistors (HBTs) operating in the reverse active mode are investigated. It is experimentally shown that the I/sub C/ is identical for the reverse and the forward modes for arbitrary doping and Ge profiles across the base to first order. In contrast, the impact of V/sub BE/ and V/sub CB/ modulation on I/sub C/ is opposite for the two modes, leading to a smaller Early voltage but more ideal collector current for the reverse mode.