K.H.G. Duh

Microwave performance of a quarter-micrometer gate low-noise pseudomorphic InGaAs/AlGaAs modulation-doped field effect transistor

We report excellent dc and millimeter-wave performance in In0.15Ga0.85As/Al0.15Ga0.85As pseudomorphic modulation-doped field effect transistors (MODFETs) with 0.25-µm-length gates. Extrinsic transconductances as high as 495 mS/mm at 300 K and unprecedented power performance in the 60-GHz range were observed. Although not yet optimized, excellent low noise characteristics, 0.9 dB, with an associated gain of 10.4 dB at 18 GHz, and a noise figure of 2.4 dB with an associated gain of 4.4 dB at 62 GHz were obtained. This is the best noise performance ever reported for a MODFET in this frequency range. These results clearly demonstrate the superiority of pseudomorphic MODFET structures in high-frequency applications.

Ultra-low-noise cryogenic high-electron-mobility transistors

Quarter-micrometer gate-length high-electron-mobility transistors (HEMTs) for cryogenic low-noise application with very low light sensitivity have been developed. At room temperature, these exhibit a noise figure of 0.4 dB with associated gain of 15 dB at 8 GHz. At a temperature of 12.5 K the minimum noise temperature of 5.3+or-1.5 K has been measured at 8.5 GHz, which is the best noise performance observed to date for any microwave transistors. The results clearly demonstrate the potential for low-temperature low-noise applications. >

A theory of the Hooge parameters of solid-state devices

Handels theory of quantum 1/f noise is applied to the Hooge parameters of bipolar transistors and various types of FETs. Very low values for the Hooge parameters α Hn and α Hp for electrons and holes are obtained. For several cases the experimental data seem to agree with the predicted theoretical limit whereas in other cases the mobility 1/f noise is masked by other noise sources. In good GaAs devices the predicted quantum limit for α Hn is reached within a factor 5-10. The theory is also applied to the Hg 1-x Cd x Te materials and devices. Because of the very low effective masses involved, the theory predicts values as high as 2 × 10-4-2 × 10-5, depending on x . What remains presently unexplained are the high values of α H for semiconductor resistors and long p-n diodes.

Millimeter-wave low-noise high electron mobility transistors

High electron mobility transistors (HEMTs) have been fabricated which demonstrate excellent millimeter-wave performance. A maximum extrinsic transconductance as high as 430 mS/mm, corresponding to an intrinsic transconductance of 580 mS/mm, was observed in these transistors. A unity current gain cutoff frequency fTas high as 80 GHz and a maximum frequency of oscillationf_{\max}of 120 GHz were projected for these HEMTs. At 40 GHz, a minimum noise figure of 2.1 dB with an associated gain of 7.0 dB has also been measured. These are the highestf_{T}, f_{\max}, and the best noise performance reported to date. The results clearly demonstrate the potential of HEMTs for millimeter-wave low-noise applications.

Hooge parameters for various FET structures

We present here values for the Hooge parameters α<inf>H</inf>of various FET structures that are one or more orders of magnitude smaller than the value 2 × 10^-3that was first proposed. It cannot be said for certain which of these values are due to mobility-fluctuation noise and which represent number-fluctuation noise, but it seems reasonable to assume that the lowest values of α<inf>H</inf>are more likely due to mobility fluctuations.We present here values for the Hooge parameters α H of various FET structures that are one or more orders of magnitude smaller than the value 2 × 10-3that was first proposed. It cannot be said for certain which of these values are due to mobility-fluctuation noise and which represent number-fluctuation noise, but it seems reasonable to assume that the lowest values of α H are more likely due to mobility fluctuations.

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>>

Burst and low-frequency generation-recombination noise in double-heterojunction bipolar transistors

The low-frequency noise in a double-heterojunction bipolar transistor (DHBT) consisted of burst noise and generation-recombination g-r noise. The current dependence of the base burst noise with floating collector was of the form IB3and the current dependence of the collector g-r noise with HF short circuited base was as IC3/2. The centers involved in the noise generation had an activation energy of about 0.40 eV, with an indication of a second center of lower energy in the collector noise.

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>>

Power and noise performance of the pseudomorphic modulation doped field effect transistor at 60 GHz

Quarter micron gate length In0.15Ga0.85As/Al0.15Ga0.55As pseudomorphic modulation doped field effect transistors (MODFETs) were grown, fabricated, and characterized. These devices exhibit outstanding DC performance with excellent pinch-off characteristics, a relatively low output conductance for a quarter micron gate field effect transistor (FET), a high reverse breakdown voltage, and transconductances as high as 495 mS/mm at 300K. Furthermore, these devices show outstanding rf performance as well. At 18 GHz, a noise figure of 0.9 dB with an associated gain of 10.4 dB was observed, and at 62 GHz, the noise figure was 2.4 dB with an associated gain of 4.4 dB. Power measurements at 62.2 GHz indicate a maximum output power density of 0.43 W/mm (Vds= 6 V) with a power gain of 3 dB, and a maximum power added efficiency of 28%, an unprecedented value. When tuned a maximum available gain of 11.7 dB was obtained at 60 GHz implying a maximum frequency of oscillation near 250 GHz. From these results it is clear that the pseudomorphic MODFET represents a very attractive choice for operation near or above 60 GHz.