Navin Parthasarathy

G-band (140-220 GHz) and W-band (75-110 GHz) InP DHBT medium power amplifiers

We report common-base medium power amplifiers designed for G-band (140-220 GHz) and W-band (75-110 GHz) in InP mesa double HBT technology. The common-base topology is preferred over common-emitter and common-collector topologies due to its superior high-frequency maximum stable gain (MSG). Base feed inductance and collector emitter overlap capacitance, however, reduce the common-base MSG. A single-sided collector contact reduces Cce and, hence, improves the MSG. A single-stage common-base tuned amplifier exhibited 7-dB small-signal gain at 176 GHz. This amplifier demonstrated 8.7-dBm output power with 5-dB associated power gain at 172 GHz. A two-stage common-base amplifier exhibited 8.1-dBm output power with 6.3-dB associated power gain at 176 GHz and demonstrated 9.1-dBm saturated output power. Another two-stage common-base amplifier exhibited 11.6-dBm output power with an associated power gain of 4.5 dB at 148 GHz. In the W-band, different designs of single-stage common-base power amplifiers demonstrated saturated output power of 15.1 dBm at 84 GHz and 13.7 dBm at 93 GHz

Wideband DHBTs using a graded carbon-doped InGaAs base

We report an InP/InGaAs/InP double heterojunction bipolar transistor (DHBT), fabricated using a mesa structure, exhibiting 282 GHz f/sub /spl tau// and 400 GHz f/sub max/. The DHBT employs a 30 nm InGaAs base with carbon doping graded from 8/spl middot/10/sup 19//cm/sup 3/ to 5/spl middot/10/sup 19//cm/sup 3/, an InP collector, and an InGaAs/InAlAs base-collector superlattice grade, with a total 217 nm collector depletion layer thickness. The low base sheet (580 /spl Omega/) and contact (<10 /spl Omega/-/spl mu/m/sup 2/) resistivities are in part responsible for the high f/sub max/ observed.

High Output Saturation and High-Linearity Uni-Traveling-Carrier Waveguide Photodiodes

Waveguide uni-traveling-carrier photodiodes (UTC-PDs) have been fabricated and tested. Output saturation currents greater than 40 mA at 1 GHz are demonstrated for a 10 mumtimes150mum photodiode (PD). The third-order intermodulation distortion is also measured and exhibits a third-order output intercept point of 43 dBm at 20 mA and 34 dBm at 40 mA for this same PD. UTC-PDs with geometries of 5 mumtimes100 mum and 10 mumtimes100 mum are also compared and it is shown that a wider waveguide PD has improved saturation characteristics due to the lower optical power density which reduces the saturation at the front end of the device

Transistor and circuit design for 100-200 GHz ICs

Compared to SiGe, InP HBTs offer superior electron transport properties but inferior scaling and parasitic reduction. Figures of merit for mixed-signal ICs are developed and HBT scaling laws introduced. Device and circuit results are summarized, including a simultaneous 450 GHz f/sub /spl tau// and 490 GHz f/sub max/ DHBT, 172-GHz amplifiers with 8.3-dBm output power and 4.5-dB associated power gain, and 150-GHz static frequency dividers (a digital circuit figure-of-merit for a device technology). To compete with advanced 100-nm SiGe processes, InP HBTs must be similarly scaled and high process yields are imperative. Described are several process modules in development: these include an emitter-base dielectric sidewall spacer for increased yield, a collector pedestal implant for reduced extrinsic C/sub cb/, and emitter junction regrowth for reduced base and emitter resistances.

G-band (140-220-GHz) InP-based HBT amplifiers

We report tuned amplifiers designed for the 140-220-GHz frequency band. The amplifiers were designed in a transferred-substrate InP-based heterojunction bipolar transistor technology that enables efficient scaling of the parasitic collector-base junction capacitance. A single-stage amplifier exhibited 6.3-dB small-signal gain at 175 GHz. Three-stage amplifiers were subsequently fabricated with one design demonstrating 12.0-dB gain at 170 GHz and a second design exhibiting 8.5-dB gain at 195 GHz.

An 8-GHz continuous-time /spl Sigma/-/spl Delta/ analog-digital converter in an InP-based HBT technology

We report an 8-GHz clock-rate, second-order continuous-time /spl Sigma/-/spl Delta/ analog-digital converter (ADC) that achieves 57.4-, 51.7-, and 40.2-dB SNR at signal sampling rates of 125, 250, and 500 Ms/s, respectively. The integrated circuit occupied 1.45-mm/sup 2/ die area, contains 76 transistors, is fabricated in an InP-based HBT technology, and dissipates /spl sim/1.8 W. We also study the effect of excess delay on modulator performance, and show that excess delay does not affect performance as long as the centroid-in-time of the digital-analog converter pulse remains stationary.

Monolithically Integrated Balanced Uni-Traveling-Carrier Photodiode with Tunable MMI Coupler for Microwave Photonic Circuits

A monolithically integrated balanced uni-traveling-carrier photodiode (UTC-PD) with a tunable 2times2 multimode interference (MMI) coupler has been fabricated and tested. Two waveguide UTC-PDs are electrically isolated using high-energy Helium implantation, and then connected in series using a monolithic metal interconnect. On chip metal-insulator-semiconductor (MIS) capacitors provide some DC decoupling. The tunable MMI coupler allows for tuning of the power balance in the PDs. Output saturation currents greater than 40 mA at 1 GHz are demonstrated for a single 10 mum times 150 mum UTC-PD. The third order intermodulation distortion (IMD3) is also measured and exhibits an output intercept point (OIP3) of 43 dBm at 20 mA and 34 dBm at 40 mA for this same UTC-PD. In the balanced configuration, the OIP3 values are therefore 49 dBm and 40 dBm. The balanced UTC-PD is also highly symmetric; the common mode rejection ratio (CMRR) was measured to be around 40 dB.

75 GHz 80 mW InP DHBT power amplifier

We report a 75 GHz MMIC power amplifier in InP/InGaAs/InP DHBT transferred-substrate technology. The amplifier has 256 /spl mu/m/sup 2/ total emitter area and exhibits a power gain of 5.5 dB at 75 GHz and a saturated output power of 19 dBm (80mW) under 1-dB gain compression. The DHBT employed by the amplifier has a lightly doped InP emitter epitaxial layer between the emitter and the emitter cap layer as a distributed ballast resistance to improve thermal stability. To our knowledge, this is the highest reported output power for a W-band HBT power amplifier.

Collector-pedestal InGaAs/InP DHBTs fabricated in a single-growth, triple-implant process

This letter reports InP/In/sub 0.53/Ga/sub 0.47/As/InP double heterojunction bipolar transistors (DHBTs) employing an N/sup +/ subcollector and N/sup +/ collector pedestal-formed by blanket Fe and patterned Si ion implants, intended to reduce the extrinsic collector-base capacitance C/sub cb/ associated with the device footprint. The Fe implant is used to compensate Si within the upper 130 nm of the N/sup +/ subcollector that lies underneath the base ohmic contact, as well as compensate the /spl sim/1-7/spl times/10/sup -7/ C/cm/sup 2/ surface charge at the interface between the indium phosphide (InP) substrate and the N/sup

An 8-GHz continuous-time /spl Sigma/-/spl Delta/ analog-digital converter in an InP-based DHBT technology

/collector drift layer. By implanting the subcollector, C/sub cb/ associated with the base interconnect pad is eliminated, and when combined with the Fe implant and selective Si pedestal implant, further reduces C/sub cb/ by creating a thick extrinsic collector region underneath the base contact. Unlike previous InP heterojunction bipolar transistor collector pedestal processes, multiple epitaxial growths are not required. The InP DHBTs here have simultaneous 352-GHz f/sub /spl tau// and 403-GHz f/sub max/. The dc current gain /spl beta//spl ap/38, BV/sub ceo/=6.0 V, BV/sub cbo/=5.4 V, and I/sub cbo/<50 pA at V/sub cb/=0.3 V.