P. Ho

A 0.15 mu m gate-length pseudomorphic HEMT

A 0.15- mu m-gate-length double-heterojunction pseudomorphic HEMT (high electron mobility transistor) that exhibits state-of-the-art power and noise performance is reported. Power results include record power-added efficiencies of 51%, 41% and 23% at 35, 60 and 94 GHz, respectively, and output powers of 139 mW at 60 GHz and 57 mW at 94 GHz. Measured minimum noise figures of 0.55 dB at 18 GHz and 1.8 dB at 60 GHz are reported. It is suggested that because of its demonstrated performance and continued rapid rate of improvement, the pseudomorphic HEMT should be the preferred transistor for a number of millimeter-wave applications, used either as a discrete device in high-performance hybrid amplifiers or integrated into GaAs-based MMICs (monolithic microwave integrated circuits).<<ETX>>

Extremely high gain, low noise InAlAs/InGaAs HEMTs grown by molecular beam epitaxy

High-performance InAlAs/InGaAs planar-doped HEMTs (high-electron-mobility transistors) lattice-matched to InP have been fabricated with a 0.25- mu m T-gate. A maximum extrinsic transconductance g/sub m/ of 900 mS/mm, corresponding to an intrinsic g/sub m/ of 1640 mS/mm, was obtained at room temperature. RF measurements at 18 GHz yielded a minimum noise figure of 0.5 dB with an associated gain of 15.2 dB and a maximum stable gain of 20.9 dB. At 58 GHz, the devices exhibited a 1.2-dB minimum noise figure with an 8.5-dB associated gain. At 63 GHz, a maximum available gain of 15.4 dB was measured for a single-stage amplifier. This value, extrapolated to -6 dB/octave, yielded a maximum frequency of oscillation f/sub max/ of 380 GHz, which is the highest f/sub max/ ever reported for any transistor. A three-stage HEMT amplifier exhibited an average noise figure of 3.0 dB with a gain of 22.0+or-0.2 dB from 60-65 GHz.<<ETX>>

Very high performance 0.15 mu m gate-length InAlAs/InGaAs/InP lattice-matched HEMTs

State-of-the-art high-electron-mobility-transistor (HEMT) devices have been fabricated on InAlAs/InGaAs/InP. Devices with 30- mu m and 50- mu m gate widths and 0.15- mu m gate length were fabricated using an all-electron-beam lithography process. After mesa formation, ohmic contacts were formed using a standard NiAuGe metallization. The contacts were annealed using a rapid thermal annealer. Typical ohmic contact resistance was approximately 0.13 Omega -mm. This is the same as the typical contact for the GaAs-based pseudomorphic HEMT result. Gates were defined using a trilayer resist scheme and recessed using a wet chemical etch to reach the desired channel current. A TiPtAu metallization forms the gate. The devices exhibited performance superior to most other low noise HEMT devices. It is found that the gate leakage current increases as recess depth increases. This current increase seems to degrade noise performance.<<ETX>>

Millimeter wave power performance of InAlAs/InGaAs/InP HEMTs

The DC and microwave power performance of both lattice-matched and pseudomorphic InAlAs/InGaAs/InP high electron mobility transistors HEMT lattice-matched to an InP substrate yielded peak power-added efficiency of 52% with power gain of 10.5 db and power density of 0.41 W/mm. When the HEMT was biased and tuned for maximum output power, a power density of 0.78 W/mm and power-added efficiency of 44% with 10.2 dB power gain were measured. At 60 GHz, a 0.15- mu m-gate-length and 50- mu m-gate-width InP-based HEMT with a pseudomorphic channel demonstrated 41% peak power-added efficiency with 7.2 dB power gain and 0.35 W/mm power density. A similar device also exhibited peak power-added efficiency of 26% with power gain of 4.9 dB and output power density of 0.2 W/mm at 94 GHz.<<ETX>>

A novel low-temperature passivation of InAlAs/InGaAs HEMT devices by MBE

The authors report the first successful passivation of an InAlAs/InGaAs/InP high electron mobility transistor (HEMT) with an InAlAs layer grown at low temperature (LT) by molecular beam epitaxy (MBE). After passivation, extrinsic transconductance, gate-drain breakdown voltage, and channel breakdown voltage are increased, while the gate leakage is reduced. RF measurement of the devices shows no degradation of the noise figure measured at 58 GHz. The authors report the result of a thermal storage test performed on the device at 230 degrees C with DC parameters monitored as a function of time. The results demonstrate that the LT passivation by MBE under ultra-high vacuum ambient is an effective novel approach to solve the problem inherent to surface-sensitive III-V devices, such as the HEMT devices reported here.<<ETX>>

V- and W-band low-noise InAlAs/InGaAs/InP HEMTs and amplifiers

Extremely low-noise O.15jim gate-length V- and W-band InGaAs I InAlAs I InP lattice-matched and pseudomorphic HEMTs have been successfully fabricated. A maximum extrinsic transconductance of 1,500mS/mm and a gate breakdown voltage of more than 1OV have been obtained for the devices. Minimum noise figures of 0.3, 0.9 and and 1.4dB have been measured for the devices at 18, 60 and 94GHz, respectively. We have also measured a maximum available gain of 13.6dB at 95GHz, corresponding to a maximum frequency of oscillation, m of 455GHz (-6dB/octave extrapolation) with the device. Based on these high performance O.l5Rm devices, a 3-stage hybrid amplifier with a minimum noise figure of 3.3dB and gain of 17.3±0.5dB from 88 to 96GHz has been built. We have also successfully demonstrated for the first time a two-stage InP-based HEMT monolithic microwave integrated circuit (MMIC) with 3.0dB noise figure and 21.0dB gain at 58GHz. These are the best device and amplifier results ever reported. The results are far superior to those obtained from the GaAs-based MESFET and HEMT technology, and clearly demonstrate the potential of the InP-based HEMT technology for very low-noise applications well into the millimeter-wave regime.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

High performance Q-band 0.15 mu m InGaAs HEMT MMIC LNA

A monolithic three-stage pseudomorphic InGaAs high-electron-mobility-transistor (HEMT) low-noise amplifier is discussed. The amplifier exhibits state-of-the-art low noise and gain performance at Q-band frequencies. It exhibits 22 dB of gain with 3-dB noise figure from 41 to 45 GHz. From 35 to 50 GHz, it has a flat gain response of over 22 dB gain across the Q-band range. The amplifier uses 0.15- mu m-gate-length GaAs-based pseudomorphic HEMTs with on-chip matching circuits and bias circuits. The chip size is 2.3 mm*1.0 mm.<<ETX>>

0.25 mu m PHEMT X-band multifunction LNA MMIC with T/R switch and attenuator achieves 1.85 dB noise figure

The performance of a 7-11-GHz LNA (low-noise amplifier) MIC (monolithic microwave integrated circuit) which advances performance and integration standards is presented. A 1.8-dB noise figure (NF), 19-dB-gain LNA is coupled with a 0.5-dB insertion loss T/R (transmit/receive) switch and switched attenuator for a MMIC with 1.85-dB NF, 18-dB gain at 10 GHz. The X-band multifunction LNA MMIC was fabricated on the GE 0.25- mu m pseudomorphic high-electron-mobility transistor (PHEMT) process. The noise figure for the MMIC is below 2.2 dB (minimum 1.85 dB), the gain is above 20 dB, and the input return loss is better than 13 dB from 7 GHz to 11 GHz. The T/R switch and 8-dB attenuator function as designed. This excellent performance can be attributed to careful measurement, accurate modeling of a large number of devices, thorough design, and careful, repeatable fabrication.<<ETX>>

Very low-noise Al0.3Ga0.7As/In0.35Ga0.65As/GaAs single quantum-well pseudomorphic HEMTs

AlGaAs/InGaAs/GaAs pseudomorphic HEMTs with an InAs mole fraction as high as 35% in the channel has been successfully fabricated. The device exhibits a maximum extrinsic transconductance of 700mS/mm. At 18GHz, a minimum noise figure of 0.55dB with 15.0dB associated gain was measured. At 94GHz, a minimum noise figure as low as 2.4dB with 5.4dB associated gain was also obtained. This is the best noise performance ever reported for GaAs-based HEMTs.

High-efficiency 0.25- mu m gate-length pseudomorphic power heterostructure FETs at millimeter-wave frequencies

Summary form only given. The authors compare the 35-GHz power performance of four different 0.25- mu m gate-length pseudomorphic AlGaAs/InGaAs/GaAs heterostructure FET (HFET) devices. The devices that are examined include the HEMT (high-electron-mobility transistor), double-heterojunction HEMT (DHHEMT), doped-channel HFET (DCHFET), and the doped-channel MODFET (DCHMODFET). A maximum 35-GHz power-added-efficiency and a power density of 49% and 0.94 W/mm were measured, for the DCHMODFET; 43% and 0.97 W/mm for the DHHEMT, 32% and 0.75 W/mm for the HEMT, and 31% and 0.77 W/mm for the DCHFET. The DC parameters that influence RF power performance were analyzed, and it was found that the I-V linearities of the DCHMODFET, DCHFET, and DHHEMT are much better than that of the HEMT and that the pinchoff characteristics of the DCHMODFET are superior to those of the DHHEMT. The first point explains why the efficiencies of the DCHMODFET and DHHEMT are significantly better than that of the HEMT. It is believed that the second point is responsible for the better efficiency in the DCHMODFET compared to the DHHEMT. >