J.J. Brown

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.

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.

CH4/H2/Ar/Cl2 electron cyclotron resonance plasma etching of via holes for InP‐based microwave devices

We report on a dry etch process for backside through‐wafer via hole fabrication in InP‐based transistors which addresses many manufacturing issues including wafer mounting schemes, degradation of the frontside ohmic metal pads, yield across two‐inch wafers, and reliability issues. Low pressure electron cyclotron resonance plasma etching using a CH4/H2/Ar/Cl2 gas chemistry is investigated and compared to other InP via etching techniques. A photoresist mask was used to define 54 μm×54 μm backside vias in substrates thinned to ∼50 μm. Post‐baking the resist served both to strengthen the mask against the plasma, and to control the profile of the through‐via. The etching was performed at a temperature of 130 °C to enhance etch product volatility while allowing a reliable wax‐mounting scheme for the thinned wafers. Etch rates of ∼1 μm/min were obtained for 950 W microwave power and 250 W rf power (−260 V). After ∼95% of the etched depth was achieved, the rf bias was reduced to minimize sputtering of the frontsi...

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-efficiency L and S-band power amplifiers with high-breakdown GaAs-based pHEMTs

Performance and reliability data for harmonically-terminated, high-efficiency microwave power amplifiers designed from active harmonic loadpull data utilizing high breakdown voltage AlGaAs-InGaAs-GaAs pHEMTs are reported. Single stage MIC amplifiers fabricated with 2/spl times/25 mm gate width pHEMTs resulted in P/sub out/=20 W and PAE=66% at 1.5 GHz and 2.2 GHz. Balanced hybrid amplifiers with these modules have been fabricated which have P/sub out/=40 W and PAE=64%. To the authors knowledge, this is the highest combination of reliable output power and efficiency ever achieved with pHEMT devices. Single stage amplifiers fabricated with a single 5 mm or 10 mm pHEMT gave P/sub out/=2 W and 4 W, respectively, with PAE=72%. All of these output powers are at power densities of 0.4 W/mm. These devices have undergone DC and RF lifetests with good results. This GaAs-based pHEMT device technology supports amplifier module designs in the 1-20 GHz frequency range.

High-efficiency GaAs-based pHEMT power amplifier technology for 1-18 GHz

Performance and reliability data for a high-efficiency microwave power amplifier design utilizing AlGaAs-InGaAs-GaAs pHEMTs are reported. A single stage MIC amplifier fabricated with a 5.6 mm gate width pHEMT resulted in P/sub out/=2.5 W and PAE=73% at 4 GHz. Twenty three amplifiers with similar performance were built with devices from 4 different wafer lots. Currently, these amplifiers are undergoing an RF lifetest and have shown no change thus far to the 2000 h point. This GaAs-based pHEMT device technology supports amplifier module designs in the 1-18 GHz frequency range with output powers up to 20 W.

An integrated, optically powered, optoelectronic 'smart' logic pixel for interconnection and computing applications

An architecture for optoelectronic interconnection and computing applications, based on the concept of supplying local power to several locations on a 2-D array of circuits using optical means, is described. Optical powering has the advantage of supplying power with reduced crosstalk while simplifying the layout complexity of the arrays. The concept is demonstrated using an integrated and optically powered optoelectronic smart logic pixel that operates variously as a thresholding amplifier, bistable switch/latch, and a signal inverter. The mode of operation is set by the intensity of an optical control beam, and the power is supplied by illumination of an integrated photovoltaic cell array. The circuits are integrated in the InGaAs(P) materials system, and have a bandwidth of 40 MHz, a data beam switching energy of 3.8 pJ, and an optoelectronic gain as high as 11. Analysis of circuit operation and fabrication, as well as comparisons with competing technologies for smart pixel interconnections, are discussed. >

Micromachining in III–V semiconductors using wet photoelectrochemical etching

Wet photoelectrochemical etching has been used to create deeply etched structures in both GaAs and InP. It was observed that the conductive n+ substrates etched quite rapidly, while semi‐insulating substrates exhibited enhanced etching only when a metal mask patterned the substrate, providing a low resistance contact for electron removal. It was further found that vertical profiles were achievable at high laser intensities, while a crystallographic taper was achieved at lower intensities. Finally, the limitations to microstructure geometry was explored in terms of the dynamics of the photogenerated carriers.

Highly selective reactive ion etch process for InP-based device fabrication using methane/hydrogen/argon

The etch rates of GaInAs and AlInAs were characterized using a mixture of methane, hydrogen, and argon as a function of self‐bias voltage. Effectively infinite etch selectivity between GaInAs and AlInAs was found for voltages below 200 V. This highly selective etch process was applied to the gate recess of a high electron mobility transistor device, and preliminary device measurements were made.

InP-based HEMTs for the realization of ultra-high efficiency millimeter wave power amplifiers

The authors have conducted a systematic effort to improve the breakdown voltage of InP-based HEMTs without compromising their high frequency performance, and have demonstrated millimeter wave circuit results that are comparable to or exceed those of the best GaAs-based PHEMTs in the critical area of power-added efficiency and output power. This improvement was accomplished by a combination of developments in material growth and device design and fabrication.<<ETX>>