T. Iwai

High-reliability InGaP/GaAs HBTs fabricated by self-aligned process

We report the achievement of high-reliability self-aligned InGaP/GaAs heterojunction bipolar transistors (HBTs) with an activation energy of 2.0 eV and a time to failure of 10/sup 6/ hours at a junction temperature of 200/spl deg/C. The reliability level is comparable to other devices in practical use. We also show a possible degradation mechanism of AlGaAs/GaAs HBTs.<<ETX>>

Slope Nucleation Method for the Growth of High-Quality 4-Dimethylamino-Methyl-4-Stilbazolium-Tosylate (DAST) Crystals

We have developed a new technique called the slope nucleation method (SNM) for the growth of high-quality 4-dimethylamino-methyl-4-stilbazolium-tosylate (DAST) crystals. This technique combines the spontaneous nucleation and subsequent growth of a single crystal into one process. The SNM features the ability to control the nucleation position and the growth orientation of DAST crystals. Many single crystals can be grown simultaneously in one process. X-ray diffraction (XRD) indicates that the SNM is effective for growing higher-quality DAST crystals as compared to conventional spontaneous nucleation and the top-seeded solution growth technique. DAST crystals with an XRD rocking curve as narrow as 20.2 arcsec full-width at half maximum (FWHM) were obtained.

Thermal and source bumps utilizing carbon nanotubes for flip-chip high power amplifiers

Carbon nanotubes (CNTs) have been successfully developed as thermal and source bumps for flip-chip high power amplifiers (HPAs). The newly developed 15 mum long CNT bumps exhibit thermal conductivity of 1400 W/m-K. A flip-chip AlGaN/GaN HEMT HPA with a gate width of 2.4 mm utilizing CNT bumps, operating voltage of 40 V, exhibits an output power of 39 dBm at, a frequency of 2.1 GHz without any degradation due to heat-up. To our knowledge, this is the first report about, a practical application of CNTs using their high thermal conductivity

63.2% high efficiency and high linearity two-stage InGaP/GaAs HBT power amplifier for personal digital cellular phone system

This paper reports on a high efficiency and high linearity two-stage InGaP/GaAs heterojunction bipolar transistor (HBT) power amplifier for the Japanese personal digital cellular phone system (PDC). Our power-stage HBT amplifier exhibited a high power added efficiency (PAE) of 68.8% and an adjacent channel leakage power (ACP) of -48 dBc. The ACP of the two-stage amplifier was improved enough for PDC with keeping a high PAE by combining of a driver-stage and this power-stage amplifiers. Our two-stage HBT power amplifier exhibited the highest PAE of 63.2% ever reported and an ACP at a 50-kHz offset frequency of -52 dBc in 1.5 GHz PDC standard at a Pout of 31 dBm under a supply voltage of 3.5 V.

An over 100 W n-GaN/n-AlGaN/GaN MIS-HEMT power amplifier for wireless base station applications

Novel n-GaN/n-AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) with Si3N4 film were fabricated on a semi-insulating (S.I.) SiC substrate. An n-GaN/n-AlGaN/GaN MIS-HEMT with a breakdown voltage of 400 V was obtained by using SiN/n-GaN cap structure. The single-chip GaN MIS-HEMT amplifier operated at 60 V achieves a high output power of 110 W with a linear gain of 13 dB at 2.14 GHz. This is the first report of an AlGaN/GaN MIS-HEMT with an over 100 W output power. The MIS-HEMT amplifier, combined with a digital pre-distortion (DPD) system, also demonstrates an adjacent channel leakage power ratio (ACLR) of less than -50 dBc for 4-carrier W-CDMA signals

42% high-efficiency two-stage HBT power-amplifier MMIC for W-CDMA cellular phone systems

This is the first paper to report on a high-efficiency two-stage heterojunction-bipolar-transistor power-amplifier monolithic microwave integrated circuit (MMIC) for 1.95-GHz wide-band code-division multiple-access (W-CDMA) cellular phone systems. Power amplifiers for W-CDMA systems are required to operate at high efficiency and high linearity over a wide range of output power levels. To obtain high efficiency at low output power (P/sub out/) as well as at the required maximum P/sub out/ and obtain a high linearity at the maximum P/sub out/, we chose near-class-B operation. To improve linearity at a medium P/sub out/ range, we suppressed the gain distortion resulting from near-class-B operation by using an adaptive biasing technique. The MMIC exhibited a power-added efficiency of 42%, the highest ever reported, a gain of 30.5 dB, and an adjacent channel leakage power ratio at a 5-MHz offset frequency of -38 dBc at a P/sub out/ of 27 dBm under a supply voltage of 3.5 V with 3.84-Mcps hybrid phase-shift keying modulation.

High efficiency and high linearity InGaP/GaAs HBT power amplifiers: matching techniques of source and load impedance to improve phase distortion and linearity

This paper reports on a matching technique of the source and load impedance focused on a phase distortion of InGaP/GaAs HBT power amplifiers to simultaneously achieve a high efficiency and a high linearity performance. Load-pull measurements were done to maximize power added efficiency (PAE) and source pull measurements to minimize the phase distortion and adjacent channel leakage power (ACP). Our HBT exhibited a high PAE of 60.7% and an ACP at a 50 kHz offset frequency of -51 dBc for 1.5 GHz /spl pi//4-shift QPSK modulated signal with an output power (P/sub cut/) of 31 dBm under a supply voltage of 3.5 V.

InGaP/GaAs power HBTs with a low bias voltage

This paper describes InGaP/GaAs heterojunction bipolar transistors (HBTs) for L-band power amplifiers with low bias voltage. A fabricated HBT with an emitter size of 2 /spl mu/m/spl times/20 /spl mu/m/spl times/64 fingers offers an output power, Pout, of 34.3 dBm and a power added efficiency, /spl eta//sub add/, of 57.7 % at 1.5 GHz with a collector bias of 3.5 V under class AB operation. The power HBT indicates an output power of over 31 dBm at a bias of as low as 2.5 V. Adjacent channel power leakage of the power HBT according to the Japanese standards of personal digital cellular phone (PDC) is -49 dBc when Pout is 31.4 dBm and /spl eta//sub add/ is 50.3% with collector bias of 3.5 V. This performance shows that InGaP/GaAs HBT is a useful device with a low bias voltage.

Single crystalline Si islands on an amorphous insulating layer recrystallized by an indirect laser heating technique for three‐dimensional integrated circuits

A new laser recrystallizing technique for producing single crystalline Si islands on an amorphous insulating layer has been developed. Si islands are recrystallized by indirect Ar ion laser heating utilizing a Si cap. This technique is an effective recrystallizing method for fabricating three‐dimensional integrated circuits. During recrystallization, this technique easily and stably produces a desired temperature profile to eliminate grain boundaries in recrystallized Si islands; the interior of the Si islands is kept cooler than the periphery and crystal growth begins from the interior. This desired temperature profile is realized because an Ar ion laser power is absorbed in the Si cap and heat flow takes place to the Si islands laterally as well as vertically from the heated Si cap through a separation cap. Damage to the underlying layer is not observed, which suggests that the laser beam power is cut in the Si cap. No grain boundaries are observed in more than 90% of the Si islands recrystallized with ...

0.2 cc HBT power amplifier module with 40% power-added efficiency for 1.95 GHz wide-band CDMA cellular phones

This paper is the first to report a high efficiency 0.2 cc power amplifier module for Wide-band CDMA (W-CDMA) cellular phones. The module achieves power-added efficiency (PAE) of 40% and adjacent channel leakage power (ACP) of -40.8 dBc at an output power level of 28 dBm with 4.096 MHz QPSK modulation.