S. Shanfield

An AlGaAs/InGaAs pseudomorphic high electron mobility transistor with improved breakdown voltage for X- and Ku-band power applications

The authors determined that RF drain current degradation is responsible for the poor power performance of wide-recessed pseudomorphic high-electron-mobility transistors (PHEMTs). A model based on surface states was proposed to explain this phenomenon, which then led to the use of charge-screen layers and a double-recessed gate process to suppress surface effects. Combined, these two modifications increased the devices gate-drain reverse breakdown voltage without causing a degradation in the transistors RF drain current. This allowed the simultaneous achievement of high power-added efficiency and high power density which established a new performance record for power PHEMTs at X- and Ku-bands. Delay time analysis of single- and double-recessed PHEMTs revealed that the benefit of a larger breakdown voltage in the latter device design came at the cost of a larger drain delay time. Drain delay accounted for 45% of the total delay when the 0.35- mu m double-recessed PHEMT was biased at V/sub ds/=6 V. >

A double-recessed Al/sub 0.24/GaAs/In/sub 0.16/GaAs pseudomorphic HEMT for Ka- and Q-band power applications

A double-recessed 0.2- mu m-gate-length pseudomorphic HEMT (PHEMT) has been demonstrated with 500 mW of output power (833 mW/mm of gate periphery), 6-dB gain, and 35% power-added efficiency (PAE) at 32 GHz. At 44 GHz, the device exhibited 494 mW of output power (823 mW/mm), 4.3-dB gain, and 30% PAE. This level of performance is attributed to excellent MBE material, optimized epitaxial layer design, and the use of individual source vias and of double recess with tight channel dimensions. Excellent 3-in-wafer uniformity was also observed: DC yield was greater than 95% and the interquartile range for all DC parameters was less than 20% of the median value (most are significantly lower).<<ETX>>

One watt, very high efficiency 10 and 18 GHz pseudomorphic HEMTs fabricated by dry first recess etching

The authors report 10- and 18-GHz power performance of double recessed 1.2-mm periphery pseudomorphic high electron mobility transistors (PsHEMTs). They have obtained demonstrably better uniformity in performance than conventionally fabricated PsHEMTs. This was accomplished by incorporating a new approach to recess formation using selective reactive ion etching of the first recess in a double recessed structure. The critical first recess was formed with exceptional uniformity using dry etching and an AlGaAs etch stop layer. Simultaneous power, gain, and power-added efficiency, representative of many devices, are summarized.<<ETX>>

An AlGaAs/InGaAs pseudomorphic high electron mobility transistor (PHEMT) for X- and Ku-band power applications

A PHEMT with record-high output power, gain and power-added efficiency at 10 and 18 GHz has been achieved due to the use of a novel method to improve the gate-drain reverse breakdown voltage. A critical surface problem was uncovered and resolved. Silicon nitride was deposited as surface passivation. The results of this work suggest that, in addition to superior low-noise performance, the PHEMT is also very promising for high-performance, power amplications in the X- to Ku-band frequency range.<<ETX>>

Ka-band GaAs HBT PIN diode switches and phase shifters

In this paper, we present results on millimeter-wave PIN diode switch arms and phase shifters fabricated in our HBT process line. The PIN diode is formed by the base-collector junction of the HBT and is therefore completely compatible with our conventional HBT process. A SPST switch arm exhibited 0.7 dB insertion loss and 21 dB isolation at 35 GHz. A high power version of this switch was capable of handling 29.5 dBm input power with less than 1 dB insertion loss at 17 V reverse bias. Low-pass/high-pass phase shifter bits with relative phase shifts of 45, 90, and 180/spl plusmn/10 degrees up to 36 GHz have also been demonstrated using HBT PIN diodes as switching elements. To our knowledge, this is the first demonstration of HBT PIN diode circuits at Ka-band. A detailed discussion of the circuit designs and measurements are given in the paper.<<ETX>>

A high power Q-band GaAs pseudomorphic HEMT monolithic amplifier

A first-pass, three stage monolithic GaAs pseudomorphic HEMT power amplifier has been developed for use over the 40 GHz to 45 GHz band. The MMIC amplifier delivers 500 to 725 mW at the one dB gain compression point. The associated power gain is 10 to 11 dB and the power added efficiency is 10 to 17%. Potential applications for this work include communication systems and phased array radars.<<ETX>>

Large periphery, high power pseudomorphic HEMTs

The authors have simultaneously demonstrated 10 W output power, 13.5 dB gain and 63% power-added efficiency on a single 16.8 mm pseudomorphic high electron mobility transistor (PHEMT) device at 2.45 GHz. This result represents the highest output power from a single transistor at S-band frequencies. The power density exhibited by the PHEMT device was 625 mW/mm which is significantly higher than a typical MESFET power density of 400 mW/mm.<<ETX>>

A high linearity, high efficiency pseudomorphic HEMT

The authors report the third-order intermodulation distortion and phase deviation of 1.2-mm periphery double pulsed doped pseudomorphic high-electron-mobility transistors (HEMTs) at high levels of power and efficiency. A device tuned for single-tone power-added efficiency (PAE) of 59% with 0.87-W output power and 10.4 associated gain at 10 GHz could provide two-tone PAE of 50% with -19 dBc IM3/C and 0.30 W/tone. Single-tone phase deviation never exceeded 18 degrees from small signal with a phase deviation slope less than 3 degrees /dB. These measurements compare favorably to those of reported GaAs-based devices with comparable output power. A dry etched double recess structure was incorporated in the device for obtaining high reverse breakdown voltage and therefore high efficiency.<<ETX>>

High gain, pulsed power AlGaAsGaAs HBTs

Abstract A layout to minimize parasitic elements which reduce the common emitter Heterojunction Bipolar Transistor (HBT) gain and efficiency is described. Layout modifications are based upon consideration of the HBT device model that predicts better performance by reducing feedback elements. Reducing the base contacts size to minimize extrinsic base-collector capacitance, and reducing inductance in the ground connection are the primary paths to better performance. The improvements in small signal and power performance for several HBT variations are described. The changes result in a 320 μm 2 emitter area HBT which operating pulsed at 10 GHz delivers 1.25 W output power with 10.5 dB associated gain and 56% power-added efficiency.