J.C. Huang

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>>

High linearity monolithic broadband pseudomorphic spike-doped MESFET amplifiers

A highly linear pseudomorphic spike-doped MESFET has been developed. This highly linear MESFET has been demonstrated at 10 GHz. Based on this device, two types of monolithic broadband amplifiers were designed and fabricated. Both the device and circuits achieved state-of-the-art linearity results while maintaining a low DC power consumption.<<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>>

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>>

Modeling intermodulation distortion in GaAs MESFETs using pulsed I-V characteristics

A technique has been developed for modeling intermodulation distortion of GaAs MESFETs using pulsed I-V drain characteristics. The technique involves measuring the drain I-V characteristic using short drain and gate pulses from a DC operating point. This pulsed I-V characteristic is used to model the nonlinearity of the drain current source. In addition, S-parameters measured about the DC bias point are used to model the gate capacitance nonlinearity. These nonlinearities are combined into a single model, and the harmonic balance method is used to simulate intermodulation performance. This technique has been used to simulate the third-order intermodulation distortion of a spike-doped MESFET and to investigate sensitivities of source and load impedance and device nonlinearities on intermodulation performance.<<ETX>>

A high-gain, low-noise 1/2- mu m pulse-doped pseudomorphic HEMT

A 1/2- mu m gate-length pulse-doped pseudomorphic high-electron-mobility transistor (HEMT) grown by MBE, which exhibits a current-gain cutoff frequency of 62 GHz, is discussed. The maximum available gain cutoff frequency was greater than 150 GHz. A minimum noise figure of 0.85 dB and associated gain of 14 dB were measured at 10 GHz. Tuned small-signal gain in a waveguide-to-microstrip test fixture at 44 GHz was 7.6 dB. When the HEMT was tuned for power, 260 mW/mm with 5-dB gain and 17% power-added efficiency were obtained at 44 GHz. These results suggest that a 1/2- mu m pseudomorphic HEMT is a viable candidate for Q-band applications.<<ETX>>