C.S. Whelan

Low noise In/sub 0.32/(AlGa)/sub 0.68/As/In/sub 0.43/Ga/sub 0.57/As metamorphic HEMT on GaAs substrate with 850 mW/mm output power density

A double-pulse-doped InAlGaAs/In/sub 0.43/Ga/sub 0.57/As metamorphic high electron mobility transistor (MHEMT) on a GaAs substrate is demonstrated with state-of-the-art noise and power performance, This 0.15 /spl mu/m T-gate MHEMT exhibits high on- and off-state breakdown (V/sub ds/>6 V and V/sub dg/>13 V, respectively) which allows biasing at V/sub ds/>5 V. The 0.6 mm device shows >27 dBm output power (850 mW/mm) at 35 GHz-the highest reported power density of any MHEMT. Additionally, a smaller gate periphery 2/spl times/50 /spl mu/m (0.1 mm) 43% MHEMT exhibits a F/sub min/=1.18 dB and 10.7 dB associated gain at 25 GHz, and also is the first noise measurement of a -40% In MHEMT. A double recess process with selective etch chemistries provides for high yields.

GaAs metamorphic HEMT (MHEMT): an attractive alternative to InP HEMTs for high performance low noise and power applications

Metamorphic HEMTs (MHEMTs) are becoming the device of choice for low cost millimeter-wave applications, where a high indium content channel is necessary for high performance. This paper will review the material properties, the processing, end the device and amplifier performance of metamorphic HEMTs with 30% to 60% indium channel content, with a focus on work done at Raytheon RF Components.

Reliability of metamorphic HEMTs on GaAs substrates

Abstract Metamorphic HEMT (MHEMT) technology enables the growth of high indium content channels on GaAs substrates, giving them the performance of InP HEMTs. MHEMT growth techniques use a graded alloy composition buffer layer structure, permitting channel indium contents exceeding 25% without strain. Potential applications include 40 Gb/s fiber optic receivers as well as LNAs for local multipoint distribution systems and satellite communications. Many such applications place stringent requirements on reliability with Belcore standards requiring 106 h median time to failure (MTTF) at 125 °C for power devices. Satellite applications require a LNA projected failure-free service of 15–30 years, implying approximately 107 h MTTF, at 85 °C. Naturally, one will ask “Is MHEMT technology reliable?” From the results of our ongoing work, we show that MHEMT reliability is similar to that of InP HEMTs with ∼106 h MTTF at 125 °C.

K-band receiver front-ends in a GaAs metamorphic HEMT process

In this paper, we present K-band receiver blocks fabricated in a state-of-the-art 0.18-/spl mu/m GaAs metamorphic high electron-mobility transistor (MHEMT) process using a 60% indium-content InGaAs channel. Several circuits are developed to demonstrate the superior noise performance and successful integration of K-band receiver components in such a process. We show a low-power three-stage low-noise amplifier (LNA) with a gain of 23 dB and a noise figure (NF) of less than 1.6 dB at 30 GHz. This LNA shows InP-like performance on a GaAs substrate with a high RF yield of 84%. This is the first report of a statistical yield analysis of an MHEMT integrated circuit. We also demonstrate on-chip integration of a single-stage amplifier with a diode subharmonic mixer for low-power and broad-band receiver performance. This down-converter exhibits a conversion loss of 3 dB, overall NF of 5 dB, and third-order input intercept point of -5 dBm from 26 to 30 GHz.

Low noise metamorphic HEMT devices and amplifiers on GaAs substrates

Excellent noise (0.41 dB minimum noise figure with 11.5 dB associated gain at 18 GHz) and linearity (third order intercept point of 37.6 dBm at 42.5 mW DC power giving a linearity figure of merit (LFOM) of 137) have been obtained for InAlAs-InGaAs metamorphic HEMTs on a GaAs substrate. These devices have been used to design and fabricate microwave and millimeter wave amplifiers. Amplifier results are presented.

A DC-45 GHz metamorphic HEMT traveling wave amplifier

Metamorphic HEMT (MHEMT) technology is capable of providing InP based HEMT performance at GaAs based HEMT levels of manufacturability and cost. This makes the MHEMT an attractive alternative for low noise, high frequency, and wide bandwidth applications. The authors describe the performance of a DC-45 GHz MHEMT traveling wave amplifier (TWA) that is well suited for broadband applications such as 40 Gb/s fiber-optic receivers. The amplifier provides a typical noise figure of 2 dB and output powers in excess of 3 dBm.

High rate CH4:H2 plasma etch processes for InP

High rate plasma etch processes for InP with smooth etched surfaces and highly anisotropic sidewall profiles were developed. A CH4:H2-based process using an electron cyclotron resonance (ECR) etcher and a reactive ion etcher (RIE) was investigated. Etch rates in excess of 120 nm/min in an ECR etcher using CH4:H2:Ar plasma and 135 nm/min in a RIE using CH4:H2:O2 were achieved in InP and produced minimal surface roughness. These etch rates are significantly faster than those previously reported.

40-Gbit/s OEIC on GaAs substrate through metamorphic buffer technology

An optoelectronic integrated circuit operating in the 1.55-/spl mu/m wavelength range was realized on GaAs substrate through metamorphic technology. High indium content layers, metamorphically grown on a GaAs substrate, were used to fabricate the optoelectronic integrated circuits (OEICs) with -3 dB bandwidth of 40 GHz and 210 V/W of calculated responsivity. The analog OEIC photoreceiver consists of a 12-/spl mu/m, top-illuminated p-i-n photodiode, and a traveling wave amplifier (TWA). This receiver shows 6 GHz wider bandwidth than a hybrid photoreceiver, which was built using comparable, but stand-alone metamorphic p-i-n diode and TWA. With the addition of a buffer amplifier, the OEIC shows 7 dB more gain than the hybrid counterpart. To our knowledge, this is the first 40 Gbit/s OEIC achieved on a GaAs substrate operating at 1.55 /spl mu/m.

W-band metamorphic HEMT with 267 mW output power

This paper reports the highest W-band power output of metamorphic HEMT (MHEMT) technology to date. 267 mW single stage performances at 90 GHz are achieved on a 0.15 micron GaAs-based production line with improved manufacturability over InP HEMT. The single stage circuits presented here are building blocks for future MHEMT power amplifier development.

95 GHz metamorphic HEMT power amplifiers on GaAs

This paper reports on the first 95 GHz metamorphic HEMT power amplifier demonstration including power as a function of temperature. Two power MHEMT materials with 53% and 53%/43% indium channels are investigated showing a slight advantage to the split channel material. At 95 GHz, G/sub max/ values ranging 8.25-10.8 dB are shown for both materials. Single stage 0.15 mm periphery amplifiers using single 4/spl times/37.5 /spl mu/m FETs show >10 dB small signal gain. Two dB compressed power data at 95 GHz yields 15.3 dBm (224 mW/mm) and PAEs up to 22.8%. Increasing temperature up to 80/spl deg/C results in output power and PAE degradation of only 0.43 dB and 2.6 percentage points, respectively. These promising results are on the path to 100-300 mW MHEMT power amplifiers at W-band with improved manufacturability over InP HEMT.