Y. Takayama

Infrared rapid thermal annealing of Si‐implanted GaAs

Conditions for post‐implantation capless annealing of GaAs, called infrared rapid thermal annealing (IRTA) using halogen lamps, were investigated. Si‐implanted GaAs (5×1012 cm−2, 150 keV) was annealed at temperatures ranging from 700 to 1100 °C for various annealing times. Annealed GaAs at 950 °C for 2–4 s shows about 75% electrical activation and 3700 cm2/Vs electron mobility without noticeable dopant diffusion and surface decomposition. Planar metal‐semiconductor field‐effect transistors (MESFET’s) fabricated on the active layer formed by this annealing method show that the technique is promising as a post‐implantation annealing method for the fabrication of GaAs MESFET’s and GaAs integrated circuits (IC’s).

Compact DC-60-GHz HJFET MMIC switches using ohmic electrode-sharing technology

Compact DC-60-GHz heterojunction field-effect transistor (HJFET) monolithic-microwave integrated-circuit (MMIC) switches have been demonstrated for millimeter-wave communications and radar systems. To reduce the MMIC chip size, a novel ohmic electrode-sharing technology (OEST) has been developed for MMIC switches with series-shunt FET configuration. Four FETs of the series-shunt single-pole double-throw (SPDT) MMIC switch were integrated into an area of approximately 0.018 mm/sup 2/. The developed MMIC switches have a high power-handling capability with low insertion loss (IL) and high isolation (Iso) at millimeter-wave frequencies. From DC to 60 GHz, the single-pole single-throw (SPST) MMIC switch achieved the IL and Iso of better than 1.64 and 20.6 dB, respectively. At 40 GHz, the IL increases by 1 dB at the input power of 21 dBm. A novel large-signal FET model for the switch circuit is presented. The simulated power-transfer performance shows the excellent agreement with the measured one. The developed MMIC switches will contribute to the low-cost and high-performance millimeter-wave communications and radar systems.

Infrared rapid thermal annealing for GaAs device fabrication

A new post‐implantation annealing technique, called infrared rapid thermal annealing (IRTA), is discussed for fabricating GaAs devices using ion implantation technology. The IRTA apparatus and capless annealing conditions are described. Also, electrical property and its uniformity of n or n+ type GaAs layers made by Si implantation to semi‐insulating GaAs followed by IRTA are presented, and compared with those made by Si3N4 capped furnace annealing. A steeper carrier concentration profile with a higher peak carrier concentration in the n type active layer made by IRTA results in a higher transconductance without any anomalous characteristics on the GaAs metal–semiconductor field‐effect transistor.

Electrical properties of S implants in GaAs activated by infrared rapid thermal annealing

S‐implanted GaAs at room temperature was annealed by several seconds radiation from halogen lamps. Differential Hall effect/sheet resistivity measurements have been used to study the annealing behavior and electrical carrier concentration profiles of S‐implanted GaAs. Electrical activation was found to increase with increasing annealing temperature up to 1100 °C. A maximum electrical activation of 78% was obtained for a dose of 5×1013 cm−2. Also, more than 5×1018 cm−3 peak carrier concentration was obtained for a dose of 1×1014 cm−2, indicating about three times higher peak concentration than that obtained after conventional furnace annealing. For higher doses, the implanted S in the annealed GaAs does not follow Gaussian distribution even after rapid annealing. Damage‐enhanced outdiffusion of S is considered to be responsible for this result.

12-GHz-Band Low-Noise GaAs Monolithic Amplifiers

One- and two-stage 12-GHz-band low-noise GaAs monolithic amplifiers have been developed for use in direct broadcasting satellite (DBS) receivers. The one-stage amplifier provides a less than 2.5-dB noise figure with more than 9.5-dB associated gain in the 11.7-12.7-GHz band. In the same frequency band, the two-stage amplifier has a less than 2.8-dB noise figure with more than 16-dB associated gain. A 0.5-µm gate closely spaced electrode FET with an ion-implanted active layer is employed in the amplifier in order to achieve a low-noise figure without reducing reproducibility. The chip size is 1 mm ×0.9 mm for the one-stage amplifier, and 1.5 mm ×0.9 mm for the two-stage amplifier.

A DC-60 GHz GaAs MMIC switch using novel distributed FET

This paper presents the broadest-band distributed FET MMIC switch ever reported for millimeter-wave applications. The developed switch with the novel structure indicated an insertion loss of less than 1.37 dB and an isolation of better than 23.1 dB with monotonous increase up to 39.6 dB from DC to 60 GHz.

Design considerations for millimeter-wave power HBTs based on gain performance analysis

Critical design issues involved in optimizing millimeter-wave power HBTs are described. Gain analysis of common-emitter (CE) and common-base (CB) HBTs is performed using analytical formulas derived based on a practical HBT model. While CB HBTs have superior maximum-gain at very high frequencies, their frequency limit is found to be determined by the carrier transit time delay. Thus, to fully exploit the potential gain in a CB HBT, it is essential to maintain a high f/sub T/ even at high collector voltages. The advantage of using CB HBTs in a multifingered device geometry is also discussed. Unlike CE HBTs, CB HBTs are capable of maintaining a high gain even if the device size is scaled up by increasing the number of emitter-fingers. Moreover, it is found that reducing the wire parasitic capacitance allows emitter ballasting resistance to be used without affecting the gain. Fabrication of HBTs based on these design considerations led to excellent power performance in a CB unit-cell HBT at 25-26 GHz, featuring output power of 740 mW and power-added efficiency of 42%.

Common base HBTs for Ka-band applications

It has been commonly accepted that common-base (CB) HBTs are more suitable for millimeter-wave power amplifiers than common-emitter HBTs due to their superior gain. However, the essential gain behavior of CB HBTs is not well understood in detail, and thus the factors limiting their mm-wave performance are not yet clarified. In this work, basic design guidelines of CB HBTs are presented based on a detailed gain performance analysis. In particular, we stress the importance of improving the f/sub T/ at high collector voltages and reducing the feedback component of wire parasitic capacitance. The analysis is in good agreement with the measured RF performance of the fabricated HBTs.

Microwave and Millimeter-Wave Transistor Devices

This paper will review the recent advances in microwave and millimeter-wave, especially above X-band, transistors and monolithic integrated circuits in Japan. GaAs and related-compound semiconductor devices including GaAs MESFETs, GaAs MMICs, two-dimensional electron gas transistors and heterojunction bipolar transistors will be focussed.

Infrared flash annealing for fabricating GaAs MESFET's

GaAs ion-implanted layers for GaAs MESFETs have been successfully annealed by several seconds radiation from halogen lamps without any encapsulants. Si-implanted GaAs (5 × 1012cm-2, 100 keV)for an active layer annealed at 950°C for 2 seconds shows 40-50 % electrical activation with no signs of thermal dissociation. High carrier concentration profiles for S-implanted n+layers formed by this technique are also achieved with only slight impurity diffusion during annealing. For confirming the applicability of the annealing method, MESFETs with 1 µm gate length and 300 µm gate width were fabricated on the active layer formed by this technique. They show 20-30 % higher transconductance than that for MESFETs fabricated on conventional furnace annealed active layer. The higher transconductance is explained by steeper carrier concentration profile with higher peak carrier concentration in the active layer annealed by this method.