100 nm gate AlGaN/GaN HEMTs on silicon with fT = 90 GHz

The realisation of 0.1 mum gate AlGaN/GaN high electron mobility transistors grown on high-resistivity silicon substrates is reported. A maximum current density of 750 mA/mm and an extrinsic transconductance of 225 mS/mm are achieved. The devices feature a record current gain cutoff frequency as high as f _T=90 GHz, the highest value ever reported from a GaN-based device grown on a silicon substrate. The results demonstrate the great potential of GaN-on-silicon technology for low-cost millimetre-wave applications.     

AlGaN/GaN HEMTs on (111) silicon substrates

AlGaN/GaN HEMTs on silicon substrates have been fabricated and their static and small-signal RF characteristics investigated. The AlGaN/GaN material structures were grown on (111) p-Si by LP-MOVPE. Devices exhibit a saturation current of 0.91 A/mm, a good pinchoff and a peak extrinsic transconductance of 122 mS/mm. A unity current gain frequency of 12.5 GHz and f_max/f_T=0.83 were obtained. The highest saturation current reported so far, static output characteristics of up to 20 V and breakdown voltage at pinchoff higher than 40 V demonstrate that the devices are capable of handling ~16 W/mm static heat dissipation     

Lattice-Matched InP-Based HEMTs with fT of 120GHz

Lattice-matched InP-based InAlAs/InGaAs HEMTs with 120GHz cutoff frequency are reported.These devices demonstrate excellent DC characteristics:the extrinsic transconductance of 600mS/mm,the threshold voltage of －1.2V,and the maximum current density of 500mA/mm.     

Direct ion-implanted 0.12 μm GaAs MESFET with ft of121 GHz and fmax of 160 GHz

An 0.12 μm gate length direct ion-implanted GaAs MESFET exhibiting excellent DC and microwave characteristics has been developed. By using a shallow implant schedule to form a highly-doped channel and an AsH₃ overpressure annealing system to optimize the shallow dopant profile, the GaAs MESFET performance was further improved. Peak transconductance of 500 mS/mm was obtained at I_ds =380 mA/mm. A noise figure of 0.9 dB with associated gain of 8.9 dB were achieved at 18 GHz. The current gain cutoff frequency f_max of 160 GHz indicates the suitability of this 0.12 μm T-gate device for millimeter-wave IC applications     

0.10 μm graded InGaAs channel InP HEMT with 305 GHzfT and 340 GHz fmax

We report here 305 GHz f_T, 340 GHz f_max, and 1550 mS/mm extrinsic g_m from a 0.10 μm In_xGa _1-xAs/In_0.62Al_0.48As/InP HEMT with x graded from 0.60 to 0.80. This device has the highest f_T yet reported for a 0.10 μm gate length and the highest combination of f _T and f_max reported for any three-terminal device. This performance is achieved by using a graded-channel design which simultaneously increases the effective indium composition of the channel while optimizing channel thickness     

fT为77GHz的蓝宝石衬底0.25μm栅长AlGaN/GaN高电子迁移率功率器件

在蓝宝石衬底上用MOCVD技术生长的AlGaN/GaN结构上制作出0.25μm栅长的高电子迁移率功率晶体管.0.25μm栅长的单指器件测到峰值跨导为250mS/mm,特征频率为77GHz.功率器件的最大电流密度达到1.07A/mm.8GHz频率下在片测试80×10μm栅宽器件的输出功率为27.04dBm,同时功率附加效率达到26.5%.     

fT为77GHz的蓝宝石衬底0.25μm栅长AlGaN/GaN高电子迁移率功率器件

在蓝宝石衬底上用MOCVD技术生长的AlGaN/GaN结构上制作出0.25μm栅长的高电子迁移率功率晶体管.0.25μm栅长的单指器件测到峰值跨导为250mS/mm,特征频率为77GHz.功率器件的最大电流密度达到1.07A/mm.8GHz频率下在片测试80×10μm栅宽器件的输出功率为27.04dBm,同时功率附加效率达到26.5%.     

Effect of gate length on DC performance of AlGaN/GaN HEMTs grown by MBE

The DC performance of AlGaN/GaN high electron mobility transistors grown by plasma-assisted molecular beam epitaxy was investigated for gate lengths in the range 0.1–1.2 μm. On 0.25 μm gate length devices we obtained 40 V_DS operation with >50 mA peak I_D. The peak drain current density was 0.44 A/mm for 100 μm gate width devices with 1.2 μm gate lengths. The extrinsic transconductance (g_m) decreased with both gate length and gate width and was 75 mS/mm for all gate widths for 0.25 μm devices. E-beam written gates typically produced a slightly lower Schottky barrier height than optically patterned gates.     

A 20 GHz 8 bit multiplexer IC implemented with 0.5 μm WNx/W-gate GaAs MESFET's

An ultrahigh-speed 8 bit multiplexer (MUX) has been developed for future-generation optical-fiber communication systems having a data rate of 20 Gb/s. This IC was fabricated using a 0.5 μm WN_x/W-gate GaAs MESFET process based on optical lithography, ion implantation, and furnace annealing for good reproducibility and high throughput. The WN_x/W bilayer gate has a low sheet resistance, improving the circuit high frequency performance. To attain 20 GHz operation, advanced circuit techniques for the source-coupled FET logic (SCFL) were introduced. A cross coupled source-follower (CCSF) was developed mainly for the highest speed buffers to enhance the bandwidth. The first-stage T-type flip-flop was designed with optimization techniques and operated up to 21.1 GHz     

Laser-assisted processing of VIAs for AlGaN/GaN HEMTs on SiC substrates

Vertical interconnect accesses (VIAs) were fabricated between the source electrode on the front and the ground on the backside of high-power microwave AlGaN/GaN high-electron mobility transistors (HEMTs) on /spl sim/400-/spl mu/m-thick silicon carbide substrates. Through-wafer microholes with an aspect ratio of up to /spl sim/ 8 were drilled using pulsed UV-laser machining and subsequently metallized using electroplating. The successful implementation of the laser-assisted VIA technology into device processing was proven by dc and RF characterization. When biased at 26 V, a saturated output power of 41.6 W with an associated power-added efficiency of 55% at 2 GHz was achieved for a 20-mm AlGaN/GaN HEMT with through-wafer VIAs.     

Millimeter-wave high-power 0.25-/spl mu/m gate-length AlGaN/GaN HEMTs on SiC substrates

Reports on the CW power performance at 20 and 30 GHz of 0.25 /spl mu/m /spl times/ 100 /spl mu/m AlGaN/GaN high electron mobility transistors (HEMTs) grown by MOCVD on semi-insulating SiC substrates. The devices exhibited current density of 1300 mA/mm, peak dc extrinsic transconductance of 275 mS/mm, unity current gain cutoff (f/sub T/) of 65 GHz, and maximum frequency of oscillation (f/sub max/) of 110 GHz. Saturated output power at 20 GHz was 6.4 W/mm with 16% power added efficiency (PAE), and output power at 1-dB compression at 30 GHz was 4.0 W/mm with 20% PAE. This is the highest power reported for 0.25-/spl mu/m gate-length devices at 20 GHz, and the 30 GHz results represent the highest frequency power data published to date on GaN-based devices.     

0.2 μm AlSb/InAs HEMTs with 5 V gate breakdown voltage

DC and microwave measurements on AlSb/InAs HEMTs with a gate length of 0.21 μm are reported. The reverse gate characteristics exhibit relatively low gate leakage current and gate-drain breakdown voltages as high as 5 V. Equivalent circuit modelling yields an f_T of 110 GHz after removal of the gate bonding pad capacitance. The bias dependence of f_max is examined indicating a significant reduction in the unilateral gain due to impact ionisation     

Transient thermal characterization of AlGaN/GaN HEMTs grown on silicon

We studied a temperature increase and a heat transfer into a substrate in a pulsed operation of 0.5 length and 150 /spl mu/m gate width AlGaN/GaN HEMTs grown on silicon. A new transient electrical characterization method is described. In combination with an optical transient interferometric mapping technique and two-dimensional thermal modeling, these methods determine the device thermal resistance to be /spl sim/70 K/W after 400 ns from the start of a pulse. We also localized the high-electron mobility transistor heat source experimentally and we extracted a thermal boundary resistance at the silicon-nitride interface of about /spl sim/7/spl times/10/sup -8/ m/sup 2/K/W. Thermal coupling at this interface may substantially influence the device thermal resistance.     

Short channel AlGaN/GaN MODFET's with 50-GHz fT and1.7-W/mm output-power at 10 GHz

A thin barrier-donor layer of 200 Å was used to increase the active input capacitance and improve the extrinsic current-gain cutoff frequency (f_t) of short-gate-length AlGaN/GaN MODFETs. 0.2-μm gate-length devices fabricated on such an epi-structure with sheet carrier density of ~8×10¹² cm^-2 and mobility of 1200 cm²/Vs showed a record f_t of 50 GHz for GaN based FETs. High channel saturation current and transconductance of 800 mA/mm and 240 mS/mm respectively were also achieved along with breakdown voltages of 80 V per μm gate-drain spacing. These excellent characteristics translated into a CW output power density of 1.7 W/mm at 10 GHz, exceeding previous record for a solid-state HEMT     

An 0.03 μm gate-length enhancement-mode InAlAs/InGaAs/InPMODFET's with 300 GHz fT and 2 S/mm extrinsictransconductance

We have developed high-performance enhancement-mode InP-based modulation-doped field-effect transistors with 0.03 μm gate-length. A record high current gain cutoff frequency exceeding 300 GHz has been achieved, and the maximum extrinsic transconductance is as high as 2 S/mm with an associated drain current of 0.5 A/mm at a drain bias of 1 V. This high performance is a result of the reduction or gate length, the use of the high barrier metal Pt as gate electrodes, and most importantly the employment of the well-developed wet-etching technology that allows the formation of a very deep gate groove while retaining small side etching. The excellent E-MODFET performance opens up the possibility of implementing ever faster high-speed circuits based on direct-coupled FET logic     

Power results at 4 GHz of AlGaN/GaN HEMTs on high resistive silicon [111] substrate

The high potential at microwave frequencies of AlGaN/GaN high electron mobility transistors (HEMTs) on high resistive silicon [111] substrate for power applications has been demonstrated in this letter. For the first time, an output power density close to 1.8 W/mm and an associated power added efficiency of 32% have been measured on a 2 /spl times/ 50 /spl times/ 0.5 /spl mu/m/sup 2/ HEMT with a linear power gain of 16 dB. These results constitute the state of the art.     

版图设计对多指AlGaN/GaN HEMTs 栅指温度影响的研究

本文利用三维热仿真方法研究了不同版图设计对多指AlGaN/GaN 高电子迁移率器件工作温度的影响。我们使用拉曼微区测温技术测量了样品的沟道温度,并用于确定材料的热导率,验证器件热模型的准确性。建立模型时特别考虑了界面热阻的作用,确保器件温度分布的仿真结果与实验测量结果一致。文中采用包含界面热阻效应的三维热模型,系统的分析了栅指数目,器件栅宽和栅栅间距等因素对AlGaN/GaN 高电子迁移率晶体管热特性的影响。最后,提出了一种优化器件栅指间距的热设计方法,能够有效降低器件工作时的最高温度。     

AlGaN/GaN HEMTs on SiC with f/sub T/ of over 120 GHz

AlGaN/GaN high electron mobility transistors (HEMTs) grown on semi-insulating SiC substrates with a 0.12 /spl mu/m gate length have been fabricated. These 0.12-/spl mu/m gate-length devices exhibited maximum drain current density as high as 1.23 A/mm and peak extrinsic transconductance of 314 mS/mm. The threshold voltage was -5.2 V. A unity current gain cutoff frequency (f/sub T/) of 121 GHz and maximum frequency of oscillation (f/sub max/) of 162 GHz were measured on these devices. These f/sub T/ and f/sub max/ values are the highest ever reported values for GaN-based HEMTs.     

AlGaN/GaN HEMTs on SiC for high power broadband applications up to 40 GHz

An overview of properties and recent achievements for AlGaN/GaN high electron mobility transistors (HEMT) on semi-insulating SiC substrate is given towards high power and broadband applications up to a frequency of 40 GHz. Starting from epitaxial growth and process technology we present state-of-the-art power results obtained at the Fraunhofer Institute (IAF) from AlGaN/GaN HEMTs on SiC. Further, a one-stage 16 GHz MMIC power amplifier circuit with 1.6 W output power is presented. This result represents the first AlGaN/GaN MMIC on SiC fabricated in Europe.     

The effect of gate leakage on the noise figure of AlGaN/GaN HEMTs

The effect of gate leakage on the noise figure of AlGaN/GaN high electron mobility transistor (HEMTs) is explored. It is shown that these devices have a sizable amount of gate leakage that cannot be ignored when measuring their noise performance. Measurements across a single sample have more than 1 dB of variation in minimum noise figure. We will show this variation is because of gate leakage. A modified van der Ziel model is used to predict this large variation and allows easy noise figure prediction of HEMT and MESFET devices.