Hidenori Shimawaki

TX and RX Front-Ends for 60GHz Band in 90nm Standard Bulk CMOS

This paper describes the design of a mm-wave power amplifier PA with reliability considerations for hot carrier injection (HCI) degradation. A 60GHz-band single-chip transmitter front- end with an output power of 6dBm for 2.6 Gb/s QPSK modulation and a single-chip receiver front-end are implemented in a standard IV 90 nm CMOS technology.

Wireless uncompressed-HDTV-signal transmission system utilizing compact 60-GHz-band transmitter and receiver

A wireless uncompressed high-definition television (HDTV) signal transmission system utilizing a 60-GHz-band transmitter and two receivers is proposed and developed for indoor use. The system is capable of transmitting video signals with 1080i/720p formats and stereo audio signals as 1-Gb/s serial data stream. The compact transmitter and receiver are highlighted, each size of which is 50 mm /spl times/ 70 mm /spl times/ 15 mm. An output peak power of 10 mW and a minimum received power of -52 dBm are achieved. The wide-beam planar antennas allow less strict alignment for the wireless equipments with a maximum transmission distance of 7 m. Furthermore, path diversity technique is introduced to reduce the opportunities of shadowing by a human body around a television set.

A normally-off GaN FET with high threshold voltage uniformity using a novel piezo neutralization technique

In this paper, we successfully demonstrate a recessed gate normally-off GaN FET on a silicon substrate with high threshold voltage (V<inf>th</inf>) uniformity and low on-resistance. In order to realize high V<inf>th</inf> uniformity, a novel V<inf>th</inf> control technique is proposed, which we call “piezo neutralization technique”. This technique includes a piezo neutralization (PNT) layer formed at the bottom of the gate recess. Since the PNT layer neutralizes the polarization charges under the gate, the V<inf>th</inf> comes to be independent of the gate-to-channel span. The fabricated normally-off GaN FET with PNT structure exhibits an excellent V<inf>th</inf> uniformity (σ(V<inf>th</inf>)=18 mV) and a state-of-the-art combination of the specific on-resistance (R<inf>on</inf>A=500 mΩmm²) and the breakdown voltage (V<inf>B</inf>≫1000 V). The normally-off GaN FETs wtih PNT structure show great promise as power devices.

High-f/sub max/ AlGaAs/InGaAs and AlGaAs/GaAs HBT's with p/sup +//p regrown base contacts

The present paper describes a new approach to fabricating high performance HBTs with low base resistance. Their base contact resistance is reduced by using MOMBE selective growth in the extrinsic base region-a key process in the fabrication of high-f/sub max/ AlGaAs/InGaAs and AlGaAs/GaAs HBTs. A p/sup +//p regrown base structure, which consists of a 40-nm-thick graded InGaAs strained layer and a heavily C-doped regrown contact layer, is used for the AlGaAs/InGaAs HBTs to reduce both their base transit time and base resistance, while preventing aluminum oxide incorporation at the regrowth interface. An h/sub fe/ of 93, an f/sub T/ of 102 GHz, and an f/sub max/ of 224 GHz are achieved for a 1.6-/spl mu/m/spl times/4.6-/spl mu/m HBT, together with reduced base push-out effects and improved reliability. AlGaAs/GaAs HBTs with an 80-nm-thick uniform base layer that have high f/sub max/ values ranging from 140-216 GHz are also fabricated using the selective growth technique. These results confirm the high potential of the proposed HBTs, especially for microwave and millimeter-wave applications. >

Characterization of current-induced degradation in Be-doped HBTs based in GaAs and InP

The changes in the device characteristics under high-bias conditions are investigated for InAlAs/InGaAs and AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with heavily Be-doped base lasers, focusing on the base current and 1/f noise characteristics. It is shown that the ideality factor of the surface recombination base current provides information on the Be movement accompanying the degradation. For stress current densities up to 1.5*10/sup 5/ A/cm/sup 2/, the Be movement in the InAlAs/InGaAs HBTs is estimated to be no more than a small fraction of the 5 nm setback layer. The 1/f noise measurement highlight the effect of current stressing on the surface recombination in the HBTs. A characteristic spectral shape is found in the noise spectra for the current-stressed AlGaAs/GaAs HBT, possibly originating from the degradation-induced carrier traps. Although both HBTs have similar electronic properties, these results illustrate the striking difference in their stress current behaviors. >

50-GHz bandwidth base-band amplifiers using GaAs-based HBTs

Base-band amplifiers have been demonstrated using AlGaAs/InGaAs HBTs with regrown base contacts. The transimpedance amplifier achieved a bandwidth of 49.3 GHz and a transimpedance gain of 43.7 dB /spl Omega/. The Darlington feedback amplifier achieved a bandwidth of 54.7 GHz and a gain of 8.2 dB. These are the widest bandwidths yet reported for lumped-circuit-design amplifiers. These performances suggest the great potential of these amplifiers for use in future optical communication and millimeter-wave applications.

A low phase-noise 38-GHz HBT MMIC oscillator utilizing a novel transmission line resonator

This paper reports on a low phase noise 38 GHz-band HBT MMIC oscillator employing a newly proposed transmission line resonator. The achieved phase noise of -114 dBc/Hz at 1 MHz offset is believed to be the lowest reported for millimeter-wave oscillators without a dielectric resonator.

Ohmic contacts to p‐GaAs with p+/p regrown structures formed by metalorganic molecular beam epitaxy

Excellent ohmic contacts to p‐GaAs are fabricated using selective growth by metalorganic molecular beam epitaxy. Specific contact resistance of about 5×10−8 Ω cm2 is achieved, without any heat treatment, at AuMn/Au and Ti/Pt/Au metal contacts, formed on p+‐GaAs layers heavily carbon‐doped to 4.4×1020 cm−3. Regrown contacts with planar and lateral p+/p structures are fabricated to clarify interface contact resistivities. A fairly low value of 7.1×10−8 Ω cm2 is established, using an equivalent circuit model, for the lateral contacts to thin p‐GaAs layers, reasonably independent of its thicknesses in the range of 9.5–95 nm. These results, in addition to excellent growth selectivity, have confirmed prospects for practical use.

A 76 GHz GaN-on-silicon power amplifier for automotive radar systems

This paper describes the first demonstration of a 76 GHz gallium nitride (GaN) power amplifier (PA) on a silicon substrate. The PA microwave monolithic IC (MMIC) was fabricated by using AlGaN/GaN FET with a maximum oscillation frequency of 160GHz and a breakdown voltage of over 50 V. For reducing transmission loss, we used a CPW line on the silicon substrate with low transmission loss of 0.5 dB/mm at 76 GHz. For precise design of the PA, a large signal model of the FET was developed. The developed CPW 3-stage PA exhibited an output of over 12 dBm with over 5 dB gain at 75–81 GHz.

Stress current behavior of InAlAs/InGaAs and AlGaAs/GaAs HBT's with polyimide passivation

InAlAs/InGaAs and AlGaAs/GaAs HBTs, with heavily Be-doped base layers, have been fabricated and their reliability under excessive forward current tested. To understand the HBT material difference, a common process based on a polyimide planarization method is applied to the fabrication. While short-term degradation induced by stress current is observed for AlGaAs/GaAs HBTs, InAlAs/InGaAs HBTs are stable up to a current density of 1.5*10/sup 5/ A/cm/sup 2/, indicating the absence of substantial Be diffusion. An analysis of base current has shown a striking contrast between the HBTs in terms of the stressing effect on the surface recombination along emitter junction periphery.<<ETX>>