The International Electron Devices Meeting (IEDM), held last year in San Francisco from December 1013, 2000, is the premier venue for both researchers and manufacturers to report their latest device results. While compound semiconductors represent only a small fraction of the work presented, other technologies based on widely differing materials such as silicon and organics are also of great relevance to the III-V community. These other technologies represent potential competition for compound semiconductors in the marketplace, but also potential opportunities for collaboration and synergy, in addition to access to applications that compound semiconductor devices alone would not be capable of. Electronic Devices HEMTs In the quest for ever higher operating frequencies, Lai and coworkers from TRW reported on the first G-Band (140220 GHz) amplifiers. Using InGaAs/InAlAs/InP PHEMT technology featuring In content greater than 70% in the channel region, gate lengths of 70 nm and a backside process to reduce substrate thickness to 50 m, ft values in excess of 300 GHz were achieved (see ). These amplifiers showed 78 dB of gain per stage at 200 GHz operation, while a three stage single-ended microstrip MMIC amplifier gave 1012 dB gain and a NF of 5.1 dB at 151 GHz. Parts fabricated using this technology included a three-stage amplifier showing 14 dB of gain with less than 7 dB of noise from 170190 GHz, and a six-stage amplifier covering the frequency range of 160215 GHz with 20 dB average gain, and a NF of 8 dB at 170 GHz, making these the highest frequency gain amplifiers reported to date. These high frequency devices will offer higher bandwidth, reduced aperture and instrument size, and narrower beam widths for radar and remote sensing applications. Other HEMT highlights include work performed by Gassler and coworkers from the University of Ulm on metamorphic InP-based HEMTs grown on GaAs substrates, with a graded AlInAs buffer to transition between the GaAs and InP lattice constant. These devices feature a composite channel comprised of a 5 nm InGaAs layer with an In content of 43%, coupled with an undoped 5 nm InP subchannel and a 10 nm InP donor layer doped 2 1018/cm3. The introduction of this InP subchannel improves device performance due to the reduction of impact ionization in InP as compared to InGaAs. The resulting device exhibited ft and fmax values of 188 and 300 GHz respectively, along with an IDSmax of 625 mA/mm and a transconductance of 850 mS/mm for 20 nm gate length devicesvalues quite comparable to InP-based HEMTs grown on more expensive InP substrates. Power HBTs In the area of III-V HBTs for power applications, both double heterostructure GaAs- and InP-based HBTs have found a wide range of uses in commercial and military applications. However, both these material systems suffer from a bandgap spike produced at the interface between the narrow bandgap base and wide bandgap collector junction, which must be reduced through bandgap grading or spacer approaches in order to optimize current transport. Dvorak and coworkers from Simon Fraser University report on another double heterostructure HBT approach using an abrupt InP/GaAsSb/InP strucuture, in which the staggered bandgap lineup between GaAsSb and InP eliminates the junction interface bandgap spike (see ). These MOCVD-grown devices used a 2025 nm strained GaAs0.6Sb0.4 base layer, carbon doped at a level of 810 1019/cm3. The resulting HBTs exhibited an ft value of 250 GHz and fmax value greater than 200 GHz, and BVCEO greater than 6 V. This represents the highest reported ft for any kind of DHBT produced with conventional processing approaches. Wide Bandgap Materials While GaAs- and InP-based devices continue to see improvements in operating frequencies, rapid improvements in power capabilities are being demonstrated in the wide bandgap GaN material system. Wu and coworkers from Cree Lighting achieved a new power record for pulsed operation of a AlGaN/GaN HEMT amplifier grown on SiC (see . Using 0.50.6 m gate lengths, these devices showed ft and fmax values of 2530 and 60100 GHz, respectively, operating at a current density of 11.3 A/mm and exhibiting a breakdown of 7080 V. The devices were flip-chip bonded to AlN, onto which all MIM capacitors, metal resistors and airbridge interconnects were fabricated. This approach improves the amplifiers thermal and electrical characteristics. With an 8 mm gate periphery and operating under a 5% duty cycle at 6 GHz, the device delivered a power density of 6.4 W/mm for a total power of 50 W. Such performance is 610 times higher than that achieved by GaAs-based devices of the same size. GaN-based HEMTs show greatly enhanced power densities as compared to GaAs-based devices, but these higher power levels increase the demands on device isolation since drain voltages may be 20 times higher. Masato and coworkers from Matsushita Electronics reported on a selective thermal oxidation process by using a Si mask over the active device area (which is oxidized to form SiO2 and subsequently etched away), while a Ga2O3 layer is formed in the desired isolation regions. The resulting leakage current between devices as compared to those formed by conventional mesa isolation was reduced by 5 orders of magnitude for devices operating at drain voltages of 120 V. In other work modifying the surface properties of GaN devices, Lee and coworkers from Daimler Chrysler and the Korea Institute of Science and Technology demonstrated that surface passivation with SiN improved HEMT output power from 0.59 W/mm to 1.45 W/mm. This improvement is attributed to the passivation of surface states, which act as a current limiter in the gate-drain region of the device. Also paying close attention to the surface behavior of GaN devices, Chumbes and coworkers from Cornell reported on using a PECVD Si3N4 process, which had initially been developed to improve RF performance through surface passivation. The Si3N4 is used as the insulator material in a AlGaN/GaN MISFET. These devices delivered 750 mA/mm with peak transconductances of 110 mS/mm, and with a 28 V bias generated 4.2 W/mm and 36% PAE at 4 GHz operation. Optical Devices Looking well past current optical network requirements to those which will be needed a decade from now, Wada from Japan s Femtosecond Technology Research Association described some of the work being done under Japan s MITI Femtosecond Technology program aimed at enabling networks to operate in the 110 Tb/s range. For these data rates, it is proposed that OTDM (optical time-division multiplexing) approaches will be implemented, which will require ultra-high-speed femtosecond laser light sources and all-optical switches. Such devices are now being fabricated, and include an InGaAsP/InP laser consisting of a gain section and a saturable absorber with a short cavity (170 m) coupled with a single-mode fiber compressor. This device was able to successfully generate a pulse train with a width of only 390 fs and a repetition rate of 500 GHz, making it suitable for OTDM applications. Other OTDM compatible components described included a Mach-Zehnder all-optical switch comprised of an InGaAsP/InP semiconductor optical amplifier array and planar lightwave circuits. Such a device has been used to demultiplex a 168 Gb/s signal down to 10.5 Gb/sthe highest demultiplexed data rate reported to date. At the other end of the spectrum, focusing not on ultimate performance, but on manufacturability, Klotzkin and coworkers from Lucent Technologies described directly-modulated Fabry-Perot and DFB lasers requiring only passive alignment and permitting high temperature operation (85C) for 2.5 Gb/s applications. Typical buried heterostructure lasers couple only 1015% of their light into a flat cleaved fiber. As a consequence, such lasers must be packaged and carefully aligned to the fiber to improve coupling efficiency. Klotzkin described a 1.3 m MQW InGaAsP laser with a narrow far field distribution (which couples more light into a passively aligned fiber), in which the laser is divided into two sectionsthe active region with a small 1 m spot size (which delivers good laser performance) coupled with a mode expander to increase the spot size to 4 m, which improves its coupling efficiency to the fiber (see ). Using such an approach, the unpackaged laser passively coupled 45% of its light to the fiber at 2.5 Gb/s operation in an uncooled state. Organic Devices Pushing optical and display applications into large area applications, where cost becomes the principal driver and III-V approaches become prohibitively expensive, organic thin films are beginning to show their potential. This was demonstrated by Sheraw and coworkers from the Pennsylvania State University and the Sarnoff Corporation, with the fabrication of organic-based thin film transistor (OTFT) circuits using hydrocarbon pentacene as the active semiconductor on a flexible, transparent, polyethylene naphthalate substrate. Inverters, ring oscillators, frequency dividers differential amplifiers and display pixel arrays were fabricated with OTFTs exhibiting mobilities of 1 cm2/V-s. The resulting ring oscillators exhibited propagation delays of less than 40 sec/stage, and below 50 sec at bias levels of 8 Vthe fastest organic circuits reported on flexible substrates to date. The ultimate in inexpensive transistor fabrication was reported by Kawase and coworkers from the University of Cambridge, who reported all-polymer transistors fabricated by ink-jet printing. With 5 m gate lengths, the printed transistors showed a mobility of 0.02 cm2/V-s and on/off ratios exceeding 1x105 (see . These devices are certainly not ready to compete with InP-based HEMTs, which exhibit mobilities above 10,000 cm2/V-s, but for large-scale kHz-range applications, this may become a very important technology. Silicon While economics and performance criteria will not find OTFTs and III-V-based devices competing for any current applications, the same thing can not be said of III-V and Si devices, especially as Si-based device performance continues to penetrate into regimes once believed to be the exclusive domain of III-V devices. Washio and coworkers from Hitachi reported on their SiGe HBT/CMOS on SOI process, which is suitable for both microwave and high speed digital applications. Using a 30 nm SiGe base, in which the Ge content ranges from 5 to 12.5%, two different versions of HBTs were produced. A high speed process with a breakdown voltage of 2.5V exhibited ft and fmax values of 76 and 180 GHz, respectively. This is the highest reported fmax for Si technology. A higher voltage version with a breakdown of 3.9V exhibited an ft and fmax of 47 and 125 GHz, respectively. Not only do these characteristics make these devices well suited for many RF applications (although the relatively low breakdown may limit their insertion in power amplifier sockets), these devices were also used in the fabrication of a differential ECL ring oscillator which showed a minimum gate delay of only 6.7 ps. While not as spectacular as the Hitachi results, an impressive RF SiGe BiCMOS process was reported by Hashimoto and coworkers from NEC. This process was capable of devices that exhibited ft and fmax values of 73 and 61 GHz, respectively and a breakdown of 2.6 V. SiGe HBTs are often viewed as the major Si-based competitor for III-V devices, but remarkable progress has also been reported for CMOS performance. Momiyama and coworkers from Fujitsu reported on an RF NMOS/SOI 80 nm gate length process operating with a gate voltage of 0.65 V and a source drain voltage of 1.5 V. These devices exhibited ft and fmax values of 140 and 60 GHz, respectivelyRF characteristics better than that reported by the Hitachi SiGe HBTs, and on par with most III-V results. And while sub 50 nm gate lengths had been the exclusive regime of high performance GaAs and InP HEMTs, Chau and coworkers from Intel reported on a 30 nm gatelength CMOS process, with NMOS and PMOS gate delays of 1.0 and 1.7 ps, and outstanding gm NMOS and PMOS values of 1200 mS/mm and 640 mS/mm, respectively.