Hua-Quen Tserng

Gate-recessed integrated E/D GaN HEMT technology with f T /f max >300 GHz

We report 1000-transistor-level monolithic circuit integration of sub-30-nm gate-recessed E/D GaN high-electron-mobility transistors with <i>fT</i> and <i>f</i>_max above 300 GHz. Simultaneous <i>fT</i>/<i>f</i>_max of 348/340 and 302/301 GHz for E- and D-mode devices, respectively, was measured, representing a 58% increase in <i>fT</i> compared with our previous report, due to improved management of RC parasitic delay. Three-terminal E- and D-mode breakdown voltage of 10.7 and 11.8 V, respectively, is limited by gate-drain breakdown.

Progress in GaN Performances and Reliability

With the DARPA Wide Bandgap Semiconductor Technology RF Thrust Contract, TriQuint Semiconductor and its partners, BAE Systems, Lockheed Martin, IQE-RF, II-VI, Nitronex, M.I.T., and R.P.I, are achieving great progress towards the overall goal of making gallium nitride a revolutionary RF technology ready to be inserted in defense and commercial applications. Performance and reliability are two critical components of success (along with cost and manufacturability). In this paper we will discuss these two aspects.

A Wideband Power Amplifier MMIC Utilizing GaN on SiC HEMT Technology

The design and performance of a wideband power amplifier MMIC suitable for electronic warfare (EW) systems and other wide bandwidth applications is presented. The amplifier utilizes dual field plate 0.25-mum GaN on SiC device technology integrated into the three metal interconnect (3MI) process flow. Experimental results for the MMIC at 30V power supply operation demonstrate greater than 10 dB of small signal gain, 9 W to 15 W saturated output power and 20% to 38% peak power added efficiency over a 1.5 GHz to 17 GHz bandwidth.

High-performance double-recessed enhancement-mode metamorphic HEMTs on 4-in GaAs substrates

Enhancement-mode InAlAs/InGaAs/GaAs metamorphic HEMTs with a composite InGaAs channel and double-recessed 0.15-/spl mu/m gate length are presented. Epilayers with a room-temperature mobility of 10 000 cm/sup 2//V-s and a sheet charge of 3.5/spl times/10/sup 12/cm/sup -2/ are grown using molecular beam epitaxy on 4-in GaAs substrates. Fully selective double-recess and buried Pt-gate processes are employed to realize uniform and true enhancement-mode operation. Excellent dc and RF characteristics are achieved with threshold voltage, maximum drain current, extrinsic transconductance, and cutoff frequency of 0.3 V, 500 mA/mm, 850 mS/mm, and 128 GHz, respectively, as measured on 100-/spl mu/m gate width devices. The load pull measurements of 300-/spl mu/m gate width devices at 35 GHz yielded a 1-dB compression point output power density of 580 mW/mm, gain of 7.2 dB, and a power-added efficiency of 44% at 5 V of drain bias.

InAlN Barrier Scaled Devices for Very High

We report excellent low-voltage (5 to ~ 10 V drain bias) microwave and millimeter-wave performance of deeply scaled InAn/AlN/GaN devices with field-plate gate of ~ 50-nm length, MBE regrown ohmic contacts, and sub-500-nm S-D spacing on four different wafers. These four wafers include also T-gate (no field-plate) devices with very thin passivation and smaller gate (~ 30 nm), which had (for reference) high fT/fmax of ~270/230 GHz, respectively, both for D- and E-mode devices. Their counterparts with field-plate gates (same gate geometry but with underlying dielectric) and 50-nm gates had lower fT/fmax but excellent performances at 10 GHz with up to 67%-69% power-added efficiency (PAE) at 6 V bias and 30 GHz with up to 14.4 dB associated gain and 2.6 W/mm and 39.6% PAE at 8 V bias. The noise figure of these devices at 10 GHz was ~ 0.25 dB with 3 V drain bias. We have measured the linearity [third-order intercept (TOI)] of 300- μm devices on another wafer with 90-nm field-plate gates: at 5 GHz and 5 V bias the devices had 31-dBm TOI with 0.31 W/mm, 18.5-dB gain, and 27.1% PAE.

f_{T}

We would like to report on AlGaN/GaN HEMTs on SiC substrate with stat-of the-art power performance at Ka-band. Power gains of 5.6, 6.3 and 6.7 dB and peak PAE of 53, 53 and 51% were measured at 35 GHz when 200-mum GaN HEMTs were biased at 10, 15 and 20 volts, respectively. At 10 GHz, 400-mum GaN HEMTs exhibited maximum PAE of 67%, power gain of 11.3 dB and power density of 5.6 W/mm when devices were biased at 30 volts. Furthermore, we have also achieved 36 to 38.7 ilBm TOI at a wide range of 10 to 26 dBm total output power for a 400-mum GaN HEMT. Very low noise figures of 1.4 dB at 26 GHz were measured on 100, 200 and 300-mum wide GaN HEMTs as well. In this work, we have demonstrated that GaN HEMTs on SiC substrate is a much superior device technology to GaAs-based pHEMT for microwave applications up through Ka-band.

and for Low-Voltage RF Applications

A new embedded transmission-line (ETL) monolithic-microwave integrated-circuit (MMIC) approach which allows flexibility in mixing different transmission-line types (i.e., coplanar and striplines) for maximum MMIC design flexibility and permits the feasibility of eliminating backside processing for low production cost is described. This ETL MMIC approach is an enabling technology allowing for low-cost batch fabrication, and high-density integration of microwave and RF components (including silicon mixed-signal products) for emerging wireless communication applications. Designs and performance results of a number of ETL MMICs are described in this paper.

AlGaN/GaN HEMTs with PAE of 53% at 35 GHz for HPA and Multi-Function MMIC Applications

We present GaAs pHEMTs demonstrating output power over 1 W/mm in Ka-band at an operating voltage of 8 V. DC, RF and reliability results are reported. Continuous wave load pull tests at 35 GHz show peak power added efficiency of 52 % and associated gain of 8 dB. The saturated output power of 1.2 W/mm is achieved. Power performance improvement is attributed to a new dielectrically defined 0.15 µm gate process which allows successful operation of these devices at a drain voltage of 8 V. Devices also show excellent small signal performance with maximum cut-off frequency as high as 107 GHz at a drain voltage of 1 V. Using three-temperature accelerated DC life tests, activation energy of 1.45 eV and median life time over 1 million hours at a channel temperature of 150 °C are estimated.

Embedded transmission-Line (ETL) MMIC for low-cost high-density wireless communication applications

A quick and reliable method to estimate the channel temperature of GaN high electron mobility transistors is extremely important in order to understand the physical degradation mechanisms as well as to extract a meaningful life time of the device. In this work, we present a simple yet powerful method to electrically measure the channel temperature of GaN HEMTs with a synchronized pulsed I-V setup. To validate the technique, we extract thermal resistance a) on the same device, multiple times, b) on multiple identical devices on the same wafer, c) on devices with different geometries and d) on identical devices with different level of degradation.

Development of Ka-Band GaAs pHEMTs with Output Power over 1 W/mm

With the DARPA Wide Bandgap Semiconductor Technology RF Thrust Contract, TriQuint Semiconductor and its partners, BAE Systems, Lockheed Martin, IQE-RF, II-VI, Nitronex, M.I.T., and R.P.I. are achieving great progress towards the overall goal of making Gallium Nitride a revolutionary RF technology ready to be inserted in defense and commercial applications. Performance and reliability are two critical components of success (along with cost and manufacturability). In this paper we will discuss these two aspects. Our emphasis is now operation at 40 V bias voltage (we had been working at 28 V). 1250 µm devices have power densities in the 6 to 9 W/mm with associated efficiencies in the low- to mid 60 % and associated gain in the 12 to 12.5 dB at 10 GHz. We are using a dual field-plate structure to optimize these performances. Very good performances have also been achieved at 18 GHz with 400 µm devices. Excellent progress has been made in reliability. Our preliminary DC and RF reliability tests at 40 V indicate a MTTF of 1E6hrs with1.3 eV activation energy at 150 0C channel temperature. Jesus Del Alamo at MIT has greatly refined our initial findings leading to a strain related theory of degradation that is driven by electric fields. Degradation can occur on the drain edge of the gate due to excessive strain given by inverse piezoelectric effect.