S-band operation of SiC power MESFET with 20 W (4.4 W/mm) output power and 60% PAE

Previous efforts have revealed instabilities in standard SiC MESFET device electrical characteristics, which have been attributed to charged surface states. This work describes the use of an undoped "spacer" layer on top of a SiC MESFET to form a "buried-channel" structure where the active current carrying channel is removed from the surface. By using this approach, the induced surface traps are physically removed from the channel region, such that the depletion depth caused by the unneutralized surface states cannot reach the conductive channel. This results in minimal RF dispersion ("gate lag") and, thus, improved RF performance. Furthermore, the buried-channel approach provides for a relatively broad and uniform transconductance (G/sub m/) with gate bias (V/sub gs/), resulting in higher efficiency MESFETs with improved linearity and lower signal distortion. SiC MESFETs having 4.8-mm gate periphery were fabricated using this buried-channel structure and were measured to have an output power of 21 W (P/sub out//spl sim/4.4 W/mm), 62% power added efficiency, and 10.6 dB power gain at 3 GHz under pulse operation. When operated at continuous wave, similar 4.8-mm gate periphery SiC MESFETs produced 9.2 W output power (P/sub out//spl sim/2 W/mm), 40% PAE, and /spl sim/7 dB associated gain at 3 GHz.     

GaAs power MESFET with 41-percent power-added efficiency at 35 GHz

A GaAs power MESFET has been optimized for Ka-Band operation. The device has an n⁺ ledge channel structure with a 0.25-μm gate on MBE-grown material. An output power density of 0.71 W/mm was achieved with 5.2-dB gain and 34% power-added efficiency. When tuned for maximum efficiency, a power-added efficiency of 41% was obtained with a power density of 0.61 W/mm and a gain of 5.6 dB     

X波段30W内匹配GaN HEMT功率器件

采用自主研发的SiC衬底GaN HEMT外延材料,研制了总栅宽为2mmGaN HEMT,利用负载牵引系统测试器件的阻抗特性,得出该器件源漏阻抗实部分别为6Ω和22Ω;设计并制作了四管芯合成器件的阻抗匹配网络,在频率为8GHz下测试,饱和输出功率为30W,功率增益在6dB以上,功率附加效率为38%,该结果目前在国内为首次报道。     

Performance of the AlGaN HEMT structure with a gate extension

The microwave performance of AlGaN/GaN HEMTs at large drain bias is reported. The device structures were grown by organometallic vapor phase epitaxy on SiC substrates with a channel sheet resistance less than 280 ohms/square. The breakdown voltage of the HEMT was improved by the composite gate structure consisting of a 0.35 /spl mu/m long silicon nitride window with a 0.18 /spl mu/m long metal overhang on either side. This produced an metal-insulator-semiconductor (MIS) gate extension toward the drain with the insulator, silicon nitride, approximately 40-nm-thick. Transistors with a 150 /spl mu/m total gate width have demonstrated a continuous wave (CW) 10 GHz output power density and power added efficiency of 16.5 W/mm and 47%, respectively when operated at 60 V drain bias. Small-signal measurements yielded an f/sub T/ and f/sub max/ of 25.7 GHz and 48.8 GHz respectively. Maximum drain current was 1.3 A/mm at +4 V on the gate, with a knee voltage of /spl sim/5 V. This brief demonstrates that AlGaN/GaN HEMTs with an optimized gate structure can extend the device operation to higher drain biases yielding higher power levels and efficiencies than have previously been observed.     

0.15μm GaN HEMT及其应用

报道了毫米波应用的0.15μm场板结构GaN HEMT。器件研制采用了76.2mm(3英寸)SiC衬底上外延生长的AlGaN/GaN异质结构材料,该材料由MOCVD技术生长并引入了掺Fe GaN缓冲层技术以提升器件击穿电压。器件栅脚和集成了场板的栅帽均由电子束光刻实现,并采用栅挖槽技术来控制器件夹断电压。研制的2×75μm栅宽GaN HEMT在24V工作电压、35GHz频率下的负载牵引测试结果显示其输出功率密度达到了4W/mm,对应的功率增益和功率附加效率分别为5dB和35%。采用该0.15μm GaN HEMT技术进行了Ka波段GaN功率MMIC的研制,所研制的功率MMIC在24V工作电压下脉冲工作时(100μs脉宽、10%占空比),29GHz频点处饱和功率达到了10.64W。     

蓝宝石衬底上槽栅型X波段增强型AlGaN/GaN HEMT

研制了一款X波段增强型AlGaN/GaN高电子迁移率晶体管(HEMT)。在3英寸(1英寸=2.54 cm)蓝宝石衬底上采用低损伤栅凹槽刻蚀技术制备了栅长为0.3μm的增强型AlGaN/GaN HEMT。所制备的增强型器件的阈值电压为0.42 V,最大跨导为401 mS/mm,导通电阻为2.7Ω·mm。器件的电流增益截止频率和最高振荡频率分别为36.1和65.2 GHz。在10 GHz下进行微波测试,增强型AlGaN/GaN HEMT的最大输出功率密度达到5.76 W/mm,最大功率附加效率为49.1%。在同一材料上制备的耗尽型器件最大输出功率密度和最大功率附加效率分别为6.16 W/mm和50.2%。增强型器件的射频特性可与在同一晶圆上制备的耗尽型器件相比拟。     

A Ku-band 3.4 W/mm power AlGaN/GaN HEMT on a sapphire substrate

This Daper describes the first domestic Ku-band power AlGaN/GaN HEMT fabricated on a sapphire substrate.The device with a gate width of 0.5 mm and a gate length of 0.35 μm has exhibited an extrinsic current gain cutoff frequency of 20 GHz and an extrinsic maximum frequency of oscillation of 75 GHz.Under V_(DS)=30 V, CW operating conditions at 14 GHz,the device exhibits a linear gain of 10.4 dB and a 3-dB-gain-compressed output power of 1.4 W with a Dower added efficiency of 41%.Under pulse operating conditions,the linear gain is 12.8 dB and the 3-dB-compressed output power is 1.7 W The power density reaches 3.4 W/mm.     

Q and V band power InGaAs MESFETs

Excellent power performance at 44 and 60 GHz demonstrated by 0.25 mu m gate InGaAs MESFETs is reported. From small-signal S-parameter measurements, these devices typically have extrinsic f/sub t/ greater than 100 GHz. At 1 dB compression point, a 150 mu m wide MESFET shows a power added efficiency of 33% with an output power of 60.8 mW (0.43 W/mm) at 44 GHz. For 200 mu m wide devices, the power added efficiency was measured to be 19% with an output power of 82 mW (0.41 W/mm) at 60 GHz. These results indicate that InGaAs MESFETs are viable millimetre-wave power devices.<>     

GaN-based optoelectronic devices on sapphire and Si substrates

A recessed gate AlGaN/GaN high-electron mobility transistor (HEMT) on sapphire (0 0 0 1), a GaN metal-semiconductor field-effect transistor (MESFET) and an InGaN multiple-quantum well green light-emitting diode (LED) on Si (1 1 1) substrates have been grown by metalorganic chemical vapor deposition. The AlGaN/GaN intermediate layers have been used for the growth of GaN MESFET and LED on Si substrates. A two-dimensional electron gas mobility as high as 9260 cm²/V s with a sheet carrier density of 4.8×10¹² cm⁻² was measured at 4.6 K for the AlGaN/GaN heterostructure on the sapphire substrate. The recessed gate device on sapphire showed a maximum extrinsic transconductance of 146 mS/mm and a drain–source current of 900 mA/mm for the AlGaN/GaN HEMT with a gate length of 2.1 μm at 25°C. The GaN MESFET on Si showed a maximum extrinsic transconductance of 25 mS/mm and a drain–source current of 169 mA/mm with a complete pinch-off for the 2.5-μm-gate length. The LED on Si exhibited an operating voltage of 18 V, a series resistance of 300 Ω, an optical output power of 10 μW and a peak emission wavelength of 505 nm with a full-width at half-maximum of 33 nm at 20 mA drive current.     

9.4-W/mm power density AlGaN-GaN HEMTs on free-standing GaN substrates

High power microwave AlGaN-GaN high electron-mobility transistors (HEMTs) on free-standing GaN substrates are demonstrated for the first time. Measured gate leakage was -2.2 /spl mu/A/mm at -20 V and -10 /spl mu/A/mm at -45 V gate bias. When operated at a drain bias of 50 V, devices showed a record continuous-wave output power density of 9.4 W/mm at 10 GHz with an associated power-added efficiency of 40%. Long-term stability of device RF operation was also examined. Under room conditions, devices driven at 25 V and 3-dB gain compression remained stable in 200 h, degrading only by 0.18 dB in output power. Such results illustrate the potential of GaN substrate technology in supporting reliable, high performance AlGaN-GaN HEMTs for microwave power applications.     

High-power InP MISFETs

InP MISFETs with SiO2 as the gate insulator and a deep channel recess have been fabricated. At 9 GHz the highest power output with 4 dB gain was 3.5 W/mm gate width with 33% power added efficiency. This power is more than twice that of the best GaAs MESFET.     

AlGaAs/InGaAs/GaAs quantum-well power MISFET at millimeter-wavefrequencies

An AlGaAs/InGaAs/GaAs quantum-well MISFET developed for power operation at millimeter-wave frequencies is described. The InGaAs channel is heavily doped to increase the sheet carrier density, resulting in a maximum current density of 700 mA/mm with a transconductance of 480 mS/mm. The 0.25-μm×50-μm device delivers a power density of 0.76 W/mm with 3.6-dB gain and 19% power-added efficiency at 60 GHz. At 5.2 dB gain, the power density is 0.55 W/mm. A similar device built on an undoped InGaAs channel had much poorer power performance and no speed advantage     

X波段GaN HEMT内匹配器件

自主研制的GaN HEMT,栅源泄漏电流从1E-4A量级减小到了1E-6A量级,有效提高了栅漏击穿电压,改善了器件工作特性. 采用MIS结构制作了2.5mm栅宽GaN HEMT,测试频率为8GHz,漏源电压为33V时,器件连续波输出功率为18.2W,功率增益为7.6dB,峰值功率附加效率为43.0%. 2.5mm×4 GaN HEMT内匹配器件,测试频率8GHz,连续波输出功率64.5W,功率增益7.2dB,功率附加效率39%.     

A Ku-band T-shaped gate GaAs power MESFET with high breakdownvoltage for satellite communications

^GaAs power MESFET's with 0.5-μm T-shaped gate for Ku-band power applications have been developed using a new self-aligned and optical lithography. It displays a maximum current density of 350 mA/mm, an uniform transconductance of 150 mS/mm and a high gate-to-drain breakdown voltage of 35 V. Both the high breakdown voltage and the uniform transconductance were achieved by the new MESFET design incorporating an undoped GaAs cap and a thick lightly doped active layers. The breakdown voltage is the highest one among the values reported on the power devices. The device exhibits 0.61 W/mm power density and 47% power added efficiency with 9.0 dB associated gain at a drain bias of 12 V and an operation frequency of 12 GHz     

0.5μm AlGaN/GaN HEMT及其应用

报道了采用I线步进光刻实现的76.2 mm SiC衬底0.5μm GaN HEMT.器件正面工艺光刻均采用了I线步进光刻来实现,背面用通孔接地.栅脚介质刻蚀采用一种优化的低损伤RIE刻蚀方法实现了60°左右的侧壁倾斜角,降低了栅脚附近峰值电场强度,提高器件性能和可靠性.研制的GaN HEMT器件fT为15 GHz,fm...     

2.9 V operation GaAs power MESFET with 31.5-dBm output power and64% power-added efficiency

A state-of-the-art GaAs power MESFET operating at a drain bias of 2.9 V has been developed using the high-low doped channel structure grown by molecular beam epitaxy. The device has 0.6 μm gate length and 16 mm gate width. The power performance tested at a 2.9 V drain bias and 900 MHz operation frequency was output power of 31.5 dBm with 11.5 dB gain and 64% power-added efficiency     

Correlation Between DC–RF Dispersion and Gate Leakage in Deeply Recessed GaN/AlGaN/GaN HEMTs

Employing deeply recessed GaN/AlGaN/GaN high-electron mobility transistors, we experimentally demonstrate the correlation between the DC-RF dispersion and the gate leakage current. It was found that both the DC-RF dispersion and the gate leakage are strongly affected by surface charging. The impact of surface charging can be controlled by using GaN/AlGaN/GaN structures with varied GaN cap thickness. In the absence of field plates, the tradeoff between the DC-RF dispersion and the gate leakage can be compromised by choosing a proper GaN cap thickness. Our optimum epistructure design yields an output power density of 5.6 W/mm with an associated power added efficiency of 72% at 28-V bias and 4-GHz frequency. The gate leakage current is as low as 30 muA/mm at up to 40-V gate-drain bias.     

GaAs/AlGaAs heterojunction MISFET's having 1-W/mm power density at 18.5 GHz

The previously reported GaAs/AlGaAs heterojunction MISFET with an undoped AlGaAs layer as an insulator has been further optimized for power operation at upper Ku band. A 300-µm gate-width device generated 320 mW of output power with 33-percent efficiency at 18.5 GHz. The corresponding power density exceeds 1 W/mm. When optimized for efficiency, the device has achieved a power added efficiency of 43 percent at 19 GHz.     

Influence of barrier thickness on the high-power performance ofAlGaN/GaN HEMTs

The dependence of current slump in AlGaN/GaN HEMTs on the thickness of the AlGaN barrier was observed. Power measurements on a 2×125×0.3 μm AlGaN/GaN HEMT made on Silicon Carbide (SiC) substrates with an AlGaN thickness of 10 nm gave a saturated output power of 1.23 W/mm at 8 GHz whereas a device with the same dimensions fabricated on samples with an AlGaN barrier of 20 nm gave a saturated output power of 2.65 W/mm at the same frequency. RF load line measurements clearly show the reduction of RF full channel current as compared to dc full channel current and the increase in the RF knee voltage compared to the dc knee voltage, with the effect being more pronounced in thin barrier samples. Passivation improved the large signal performance of these devices. A 1×150×0.3 μm transistor made on AlGaN(20 nm)/GaN structure gave a saturated output power of 10.7 W/mm (40% power added efficiency) at 10 GHz after passivation. This represents the state of the art microwave power density for AlGaN/GaN HEMTs. Heating of the transistors during high-power operation of these devices becomes the important factor in limiting their performance after passivation     

InGaAs field-effect transistors with submicron gates forK-band applications

Depletion mode InGaAs microwave power MISFETs with 0.7 μm gate lengths and 0.2 mm gate widths have been fabricated using an epitaxial process. The devices employed a plasma deposited silicon dioxide gate insulator. The RF power performance at 18 GHz, 20 GHz, and 23 GHz is presented. An output power density of 1.04 W/mm with a corresponding power gain and power-added efficiency of 3.7 dB and 40%, respectively, was obtained at 18 GHz. This is the highest output power density obtained for an InGaAs based transistor on InP at K-band. Record output power densities for an InGaAs MISFET were also demonstrated to the stable within 3% over 17 hours of continuous operation at 18 GHz