Takyiu Liu

On-state and off-state breakdown in GaInAs/InP composite-channel HEMT's with variable GaInAs channel thickness

Short-channel Ga/sub 0.47/In/sub 0.53/As high electron mobility transistors (HEMTs) suffer from low breakdown voltages due to enhanced impact-ionization effects in the narrow bandgap channel. This could limit the application of single-channel devices to medium power millimeter-wave systems. A composite Ga/sub 0.47/In/sub 0.53/As/InP channel, which exploits the high electron mobility of Ga/sub 0.47/In/sub 0.53/As at low electric fields, and the low impact-ionization and high electron saturation velocity of InP at high electric fields can overcome this limitation. In this paper we study on-state and off-state breakdown of Ga/sub 0.47/In/sub 0.53/As/InP composite-channel HEMTs with a variable GaInAs channel thickness of 30, 50, and 100 /spl Aring/. Reduction of channel thickness leads to the improvement of both on-state and off-state breakdown voltages. In on-state conditions, the enhancement in the effective Ga/sub 0.47/In/sub 0.53/As channel bandgap that takes place when the channel thickness is reduced to the order of the de Broglie wavelength (channel quantization) effectively enhances the threshold energy for impact-ionization, which is further reduced by real space transfer of electrons from the Ga/sub 0.47/In/sub 0.53/As into the wider bandgap InP. Channel thickness reduction also causes a decrease in the sheet carrier concentration in the extrinsic gate-drain region and therefore, a reduction of the electric field beneath the gate. This, together with the adoption of an Al/sub 0.6/In/sub 0.4/As Schottky layer (increasing the gate Schottky barrier height), leads to excellent values of the gate-drain breakdown voltage. In conclusion, composite channel InAlAs/GaInAs/InP HEMTs, thanks to the combined effect of effective band-gap increase, enhanced real space transfer into InP, and sheet carrier density reduction, allow a good trade-off between current driving capability and both on-state and off-state breakdown voltage.

An InP-based HBT fab for high-speed digital, analog, mixed-signal, and optoelectronic ICs

Integrated circuits (ICs) utilizing indium phosphide based heterojunction bipolar transistors (HBTs) have set numerous speed and bandwidth records over the past several years. This paper describes the extension of that HBT IC technology to an IC fabrication capability which is quite versatile in being able to produce digital, analog, mixed signal, and optoelectronic ICs within the same process. This enables the fab line to quickly respond to varying demands. Three ICs are discussed which exemplify the capability of this fab: (1) a 7 GHz 12-bit accumulator; (2) a nearly ideal continuous-time-sampling second-order /spl Delta//spl Sigma/ modulator operating at a 3.2 GHz sample rate; and (3) a monolithic 4-channel optoelectronic receiver array capable of 20 Gb/s operation.

Very low noise and low power operation of cryogenic AlInAs/GaInAs/InP HFET's

The cryogenic performance of 0.15 /spl mu/m gate length AlInAs/GaInAs/InP devices is reported. A noise temperature of less than 10 K (less than five times over quantum limit hf/k) is demonstrated at 40 GHz with a power consumption of less than 0.6 mW under optimal noise bias condition. With about 5 K penalty in noise performance at 40 GHz, the devices could be operated with as little as 60 /spl mu/W total power consumption. An interpretation of the measured noise performance with the help of a noise model, room temperature S-parameters and DC characteristics (measured at room and cryogenic temperatures) is offered.<<ETX>>

Effects of channel quantization and temperature on off-state and on-state breakdown in composite channel and conventional InP-based HEMTs

On- and off- state breakdown effects in composite channel and conventional InP-based HEMTs are studied by means of electrical measurements, and electroluminescence spectroscopy. We demonstrate that channel quantization increases off-state and on-state breakdown voltage. The temperature coefficient of the electron impact ionization rate in In/sub 0.53/Ga/sub 0.47/As has been studied. Differently from what happens in GaAs-based devices, carrier multiplication increases on increasing the temperature.

High performance, high yield millimeter-wave MMIC LNAs using InP HEMTs

A millimeter-wave MMIC low noise amplifier chip set has been developed. Based on the InP HEMT technology, these LNAs provide state-of-the-art performance as well as excellent yield and repeatability. With greater than 50% chip yield, a three-stage Q-band LNA design achieved 26 to 31 dB of gain from 42 to 50 GHz and 1.8 dB average noise figure from 43.3 to 45.7 GHz. In addition, there are six other LNA designs including a four-stage V-band LNA with 28 dB of gain and 2.3 dB noise figure and a two-stage balanced Q-band LNA that provided 17 dB of gain and has greater than 61% yield.

InP-based HEMT's with Al/sub 0.48/In/sub 0.52/As/sub x/P/sub 1-x/ Schottky layers

In this letter we report on the DC and RF performance of InP-based HEMTs with Al/sub 0.48/In/sub 0.52/As/sub x/P/sub 1-x/ Schottky layers and GaInAs/InP composite channels. By replacing the Al/sub 0.48/In/sub 0.52/As Schottky layer with Al/sub 0.48/In/sub 0.52/As/sub x/P/sub 1-x/ we have been able to increase the bandgap of the Schottky layer and achieve record breakdown voltages for 0.15 /spl mu/m gate-length InP-based HEMTs. The 0.15 /spl mu/m gate-length HEMTs have gate-to-drain breakdown voltages of over 13 V with current densities of 620 mA/mm and maximum transconductances of 730 mS/mm. On a wafer with a higher sheet charge we have obtained gate-to-drain breakdown voltages of 10.5 V with current densities of over 900 mA/mm. These are the highest breakdown voltages reported for 0.15 /spl mu/m gate-length InP-based HEMTs with such high current densities. At 10 GHz a 450 /spl mu/m wide HEMT has demonstrated 350 mW (780 mW/mm) of output power with power-added efficiency of 60% and 12 dB gain.<<ETX>>

Millimeter-wave waveguide-bandwidth cryogenically-coolable InP HEMT amplifiers

The design, construction and performance of 65-90 GHz and 75-110 GHz low-noise cryogenically-coolable amplifiers are presented. A comparison between modeled and measured performance is shown. A laboratory receiver exhibiting an average noise of 50 K across 65-90 GHz and 70 K across 75-110 GHz is described. These are the widest band and lowest noise HEMT receivers ever reported at these frequencies.

Manufacturability of 0.1- mu m millimeterwave low-noise InP HEMTs

Reports on the manufacturability of state-of-the-art passivated 0.1- mu m low-noise InP HEMTs (high electron mobility transistors). These HEMTs offer an attractive, cost-effective solution to millimeter-wave satellite communications. The authors discuss their yield and reproducibility, as well as typical performance at V- and W-bands.<<ETX>>

High-performance microwave power AlInAs/GaInAs/InP double heterojunction bipolar transistors with compositionally graded base-collector junction

We report, for the first time, on the use of compositional grading at the base-collector (B-C) junction of AlInAs/GaInAs/InP double heterojunction bipolar transistors (HBT) to achieve high-performance devices for microwave power and analog circuit applications. To overcome the conduction band potential barrier at the B-C junction, we have inserted an n-GaInAs spacer and a novel 100 nm compositional grade between the GaInAs base and the wide bandgap InP Collector. A base-collector breakdown voltage of 32 V, collector-emitter breakdown voltage of 26 V, and a f/sub max/ of 93 GHz have been achieved. Preliminary power measurements at 10 GHz on 240 /spl mu/m/sup 2/ emitter DHBTs resulted in over 5 W/mm output power at a collector bias of 10 V.<<ETX>>

A 2-GHZ three-stage AlInAs-GaInAs-InP HEMT MMIC low-noise amplifier

A three-stage monolithic microwave integrated circuit (MMIC) low-noise amplifier (LNA) has been fabricated using 0.15- mu m-gate-length, InP-based (AlInAs-GaInAs) high electron mobility transistor (HEMT) technology. The LNA exhibited less than 0.5-dB noise figure and greater than 35-dB gain from 2.25 to 2.5 GHz. The input and output return loss exceeded 15 dB across the band. The results are believed to be the best reported to date for a MMIC amplifier in this frequency range.<<ETX>>