Si-Containing Recessed Ohmic Contacts and 210 GHz Quaternary Barrier InAlGaN High-Electron-Mobility Transistors (original) (raw)
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220GHz Quaternary Barrier InAlGaN/AlN/GaN HEMTs
IEEE Electron Device Letters, 2011
Depletion-mode high-electron mobility transistors (HEMTs) based on a quaternary barrier In0.13Al0.83Ga0.04 N/AlN/GaN heterostructure on SiC substrate were fabricated. The 66-nm-long gate device shows a dc drain current density of 2.1 A/mm, a peak extrinsic transconductance of 548 mS/mm, and a record current gain cutoff frequency fT of 220 GHz for quaternary barrier GaN-based HEMTs, which is also among the highest fT for all GaN-based HEMTs. The large Lg ·fT product of 14.5 GHz ·μm with a gate-length-to-barrier-thickness aspect ratio of 5.8 indicates a high effective electron velocity of 0.9 ×107 cm/s, attributed to a high electron Hall mobility (1790 cm2/V ·s at an ns of 1.8 ×1013-2)-the highest reported in GaN-channel HEMTs with In-containing barriers. An intrinsic electron velocity of 1.7 ×107 cm/s, extracted from conventional Moll delay-time analysis, is comparable to that reported in the state-of-art AlGaN/GaN HEMTs.
Fabrication and Characterization of Thin-Barrier {Al}_{0.5}{Ga}_{0.5}{N/AlN/GaN} HEMTs
IEEE Electron Device Letters, 2011
The growth, fabrication, and performance of Al 0.5 Ga 0.5 N/AlN/GaN high-electron-mobility transistors (HEMTs) with a total barrier thickness of 7 nm are reported. An optimized surface passivation and an Ohmic recess etch yield HEMTs exhibiting 0.72 S/mm peak extrinsic DC transconductance at a current density of 0.47 A/mm. Devices with a gate length of 90 nm achieve 78 GHz unity-current-gain frequency and up to 166 GHz maximum frequency of oscillation. The minimum noise figure at 10 GHz is 0.52 dB with an associated gain of 9.5 dB.
Evaluation of an InAlN/AlN/GaN HEMT with Ta‐based ohmic contacts and PECVD SiN passivation
physica status solidi c, 2014
An InAlN/AlN/GaN HEMT with Au-free Ta-based ohmic contacts and a high-quality PECVD SiN passivation is reported. The ohmic contacts were annealed at 550 °C, resulting in a contact resistance of 0.64 Ωmm. The gate length was 50 nm. The device performance and the process were evaluated by performing DC-, pulsed IV-, RF-, and load-pull measurements. It was observed that current slump was effectively mitigated by the pas-sivation layer. The DC channel current density increased by 71 % to 1170 mA/mm at the knee of the IV curve, and the transconductance increased from 382 to 477 mS/mm after passivation. At the same time the gate leakage increased, and the extrinsic f max decreased from 207 to 140 GHz. Output powers of 4.1 and 3.5 W/mm were measured after passivation at 31 and 40 GHz, respectively.
IEEE Transactions on Electron Devices, 2010
Design considerations and performance of n ++ GaN/InAlN/AlN/GaN normally off high-electron mobility transistors (HEMTs) are analyzed. Selective and damage-free dry etching of the gate recess through the GaN cap down to a 1-nm-thick InAlN barrier secures positive threshold voltage, while the thickness and the doping of the GaN cap influence the HEMT direct current and microwave performance. The cap doping density was suggested to be 2 × 10 20 cm −3. To screen the channel from the surface traps, the needed cap thickness was estimated to be only 6 nm. Design is proved by an experiment showing a constant value of the HEMT dynamical access resistance, while a single-pulse experiment indicated almost collapse-free performance. On the other hand, it is found that the n ++ GaN cap does not contribute to the HEMT drain current conduction, nor does it provide a path for the OFF-state breakdown. HEMTs with a gate length of 0.25 μm and a 4-μm source-to-drain distance show a drain-to-source current of 0.8 A/mm, a transconductance of 440 mS/mm, a threshold voltage of ∼0.4 V, and a cutoff frequency of 50 GHz. A thin and highly doped GaN cap is also found to be suitable for the processing of normally on HEMTs by adopting the nonrecessed gate separated from the cap by insulation.
Low thermal budget Hf/Al/Ta ohmic contacts for InAlN/GaN-on-Si HEMTs with enhanced breakdown voltage
Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2014
The authors have studied the electrical characteristics of Hf/Al/Ta ohmic contacts on In 0.18 Al 0.82 N/GaN heterostructure grown on Si (111) substrate. With annealing at 600 C in vacuum (which is 200ClowerthanthatfortraditionalTi/Al/Ni/Aucontacts),aminimumohmiccontactresistanceof200 C lower than that for traditional Ti/Al/Ni/Au contacts), a minimum ohmic contact resistance of 200ClowerthanthatfortraditionalTi/Al/Ni/Aucontacts),aminimumohmiccontactresistanceof0.58 XÁmm and specific contact resistivity of $6.75 Â 10 À6 XÁcm 2 are obtained. The minimum contact resistance of Hf/Al/Ta contacts is comparable to that of Ti/Al/Ni/Au contacts. Owing to the lower annealing temperature, Hf/Al/Ta contacts exhibit better surface morphology and edge acuity. More importantly, Hf/Al/Ta contacts show a smooth interface with In 0.18 Al 0.82 N/GaN, whereas spike structures that penetrate the In 0.18 Al 0.82 N layer are observed for Ti/Al/Ni/Au contacts. As a result, the source-carrier-injection induced breakdown mechanism is reduced in the In 0.18 Al 0.82 N/GaN-on-Si high electron mobility transistors (HEMTs) with Hf/Al/Ta ohmic contacts, thereby leading to an improved three-terminal off-state breakdown voltage by about 100 V
IEEE Electron Device Letters, 2000
This letter reports AlGaN/GaN high-electron mobility transistors with capless activation annealing of implanted Si for nonalloyed ohmic contacts. Source and drain areas were implanted with an Si dose of I x 10(16) cm(-2) and were activated at similar to 1260 degrees C in a metal-organic chemical vapor deposition system in ammonia and nitrogen at atmospheric pressure. Nonalloyed ohmic contacts to ion-implanted devices showed a contact resistance of 0.96 Omega (.) mm to the channel. An output power density of 5 W/mm was measured at 4 GHz, with 58% power-added efficiency and a gain of 11.7 dB at a drain bias of 30 V.
2011
Ohmic regrowth by molecular beam epitaxy (MBE) has been investigated for metal-face InAlN/AlN/GaN high electron mobility transistors (HEMTs) for the first time. Using SiO 2 mask n þ-GaN was regrown in the source/drain region while deposition on the mask was lifted off in buffered HF after regrowth. The lowest contact resistance measured was 0.40 AE 0.23 V mm by the transmission line method (TLM) in this initial study. The peak output current density of 1.25 A/mm at V gs ¼ 3 V and extrinsic transconductance of 264 mS/mm at V ds ¼ 5 V were observed in 500-nm gate length InAlN/Al/GaN HEMTs passivated by SiN with regrowth contacts.
Fabrication and Characterization of Thin-Barrier AlGaN/AlN/GaN HEMTs
IEEE Electron Device Letters, 2011
The growth, fabrication, and performance of Al 0.5 Ga 0.5 N/AlN/GaN high-electron-mobility transistors (HEMTs) with a total barrier thickness of 7 nm are reported. An optimized surface passivation and an Ohmic recess etch yield HEMTs exhibiting 0.72 S/mm peak extrinsic DC transconductance at a current density of 0.47 A/mm. Devices with a gate length of 90 nm achieve 78 GHz unity-current-gain frequency and up to 166 GHz maximum frequency of oscillation. The minimum noise figure at 10 GHz is 0.52 dB with an associated gain of 9.5 dB.
AlN/GaN Insulated-Gate HEMTs With 2.3 A/mm Output Current and 480 mS/mm Transconductance
IEEE Electron Device Letters, 2008
High-electron mobility transistors (HEMTs) based on ultrathin AIN/GaN heterostructures with a 3.5-nm AlN barrier and a 3-nm Al2O3 gate dielectric have been investigated. Owing to the optimized AIN/GaN interface, very high carrier mobility (~1400 cm2/V ldr s) and high 2-D electron-gas density (~2.7times1013/cm2) resulted in a record low sheet resistance (~165 Omega/sq). The resultant HEMTs showed a maximum dc output current density of ~2.3 A/mm and a peak extrinsic transconductance gm,ext~480 mS/mm (corresponding to gm,int~1 S/mm). An fT/fmax of 52/60 GHz was measured on 0.25times60 mum2 gate HEMTs. With further improvements of the ohmic contacts, the gate dielectric, and the lowering of the buffer leakage, the presented results suggest that, by using AIN/GaN heterojunctions, it may be possible to push the performance of nitride HEMTs to current, power, and speed levels that are currently unachievable in AlGaN/GaN technology.
Applied Physics Express, 2011
AlN/GaN high-electron-mobility transistors (HEMTs) capped with an in-situ grown SiN have been successfully developed on 100 mm Si substrates. A unique combination of maximum output current density exceeding 2 A/mm and a record extrinsic transconductance above 600 mS/ mm has been reached, which is well beyond the highest reported values of any GaN-on-Si HEMTs. The current gain extrinsic cutoff frequency f T and the maximum oscillation frequency f max were 85 and 103 GHz with 0.16-m gate length, respectively, resulting in a high f T Á L g product that promises low-cost, high performance millimeter wave electronics. #