P.F. Marsh

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.

High indium metamorphic HEMT on a GaAs substrate

Metamorphic growth of device structures on GaAs substrates has advanced rapidly in recent years. High quality electronic and optical devices have been demonstrated. Also long-term reliability has been achieved with low noise MHEMT devices. Most of the development emphasis has been with structures conventionally grown on InP substrates. This work is motivated by the lower cost, larger diameter, and greater robustness of GaAs substrates compared to InP substrates. However an important characteristic of metamorphic growth is the degree of freedom in choosing the In/sub x/(GaAl)/sub 1-x/As composition and consequently the lattice constant between GaAs and InAs. Consequently new device structures can be achieved which are not possible by pseudomorphic growth on either GaAs or InP substrates. In this effort, solid source MBE was used to grow metamorphic HEMT structures with high indium content. For the conventional MHEMT, the indium concentration is graded to In/sub 0.52/Al/sub 0.48/As to expand the lattice constant to that of InP. Here the indium content was graded to In/sub 0.64/Al/sub 0.36/As to achieve a larger lattice constant than InP. The resulting surface roughness was examined by AFM. For a 25 /spl mu/m x 25 /spl mu/m area, the RMS roughness was 12/spl Aring/ which is very similar to the roughness present in the conventional MHEMT with less indium content.

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.

Properties of metamorphic materials and device structures on GaAs substrates

In this work, the structural, optical, and electrical properties of metamorphic films are examined and compared to non-metamorphic films. Results for electrical and optical devices are presented. Finally the reliability of metamorphic HEMTs is examined.

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.

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.

Material properties and performance of metamorphic optoelectronic integrated circuits grown by molecular beam epitaxy on GaAs substrates

Solid source molecular beam epitaxy was used to deposit in a continuous process an integrated metamorphic high electron mobility transistor (HEMT) and PIN photodiode structure. A metamorphic buffer layer was first grown on a GaAs substrate to expand the lattice constant to that of In0.53Ga0.47As used in the device layers. The HEMT layers were subsequently grown followed by the PIN diode structure. Cross-sectional and plan-view transmission electron micrographs showed planar layer interfaces and a dislocation density in the device layers of 1×106 cm−2. The device characteristics of the HEMT transistors were not adversely affected by growth of the PIN structure on top. Also the bandwidth and responsivity of the metamorphic PIN photodiode were comparable to an InP PIN photodiode with similar dark currents. The integrated HEMT/PIN diode circuit had a 3 dB bandwidth 20% greater than a hybrid combination of devices due to a decrease in parasitic losses from device interconnects. The frequency performances of ci...

High-frequency metamorphic p-i-n photodiodes and high-electron mobility transistor transimpedance amplifiers: Candidates for fiber-optic communications

Solid source molecular-beam epitaxy was used to grow metamorphic films on GaAs substrates for optical (1.55 μ) p-i-n photodetectors and transimpedance amplifiers which are key components in a fiber-optic receiver. The p-i-n device structure incorporated an In0.53Ga0.47As photoabsorption layer while the transimpedance amplifier contained a metamorphic high-electron mobility transistor structure with an In0.60Ga0.40As channel layer. All layers were arsenide based which simplified material growth. A 10-μm-diam photodiode exhibited a −3 dB bandwidth of 52 GHz, a responsivity of 0.52 A/W corresponding to an external quantum efficiency of 42%, and a dark current of 7 nA at a 10 V reverse bias. The transimpedance amplifier demonstrated a power gain of 16 dB with a −3 dB bandwidth of 45 GHz. The transistors in the amplifier exhibited a dc reliability of 3×106 h at 125 °C. These performances are very promising for the application of metamorphic devices in the next generation 40 Gbit/s fiber-optic communication system.Solid source molecular-beam epitaxy was used to grow metamorphic films on GaAs substrates for optical (1.55 μ) p-i-n photodetectors and transimpedance amplifiers which are key components in a fiber-optic receiver. The p-i-n device structure incorporated an In0.53Ga0.47As photoabsorption layer while the transimpedance amplifier contained a metamorphic high-electron mobility transistor structure with an In0.60Ga0.40As channel layer. All layers were arsenide based which simplified material growth. A 10-μm-diam photodiode exhibited a −3 dB bandwidth of 52 GHz, a responsivity of 0.52 A/W corresponding to an external quantum efficiency of 42%, and a dark current of 7 nA at a 10 V reverse bias. The transimpedance amplifier demonstrated a power gain of 16 dB with a −3 dB bandwidth of 45 GHz. The transistors in the amplifier exhibited a dc reliability of 3×106 h at 125 °C. These performances are very promising for the application of metamorphic devices in the next generation 40 Gbit/s fiber-optic communication system.

W-band power metamorphic HEMT technology on GaAs

Our 0.15 um power MHEMT development at W-band includes comparison of single (53%) and split channel (53/43%) material. Preliminary single stage microstrip amplifier results yield 225 mW/mm and >10dB small signal gain at 95 GHz.

Metamorphic optoelectronic integrated circuits

As the required operational bandwidth of photoreceivers is increased, it becomes desirable to monolithically integrate photodiodes and transistors in order to optimize performance and enhance yield. In this paper we describe our demonstration of material and process capabilities which allow us to integrate high electron mobility transistors and 1.55 /spl mu/m PIN photodiodes on one substrate. The demonstration vehicles used for this are a DC-45 GHz traveling wave amplifier and a photodiode with 12 /spl mu/m optical windows. Measured results of three interconnection approaches (standard attenuator, optimized lossy match, buffer amplifier) are described.