NOTFET: a high-frequency InP nonlinear transistor

A device called the nonlinearly optimized transconductance field-effect transistor (NOTFET) has been developed for nonlinear circuit applications. An InP NOTFET with two g_m peaks based on InGaAs and InAlAs channels was designed fabricated, and tested for harmonic generation up to 12 GHz, demonstrating the device concept and its advantages compared to conventional FETs and HEMTs. Multipeak g_m/V_GS characteristics also can be obtained by using a multiheterojunction material structure with uncoupled quantum wells, a possibility which is under investigation     

Impact of surface layer on In0.52Al0.48As/In0.53Ga0.47As/InP high electron mobilitytransistors

The surface potential of FETs has shown a strong effect on the channel potential and charge control in the channel. A study of the role of undoped versus doped cap layers in In_0.52Al_0.48As-In_0.53Ga_0.47 As-InP high-electron-mobility transistors (HEMT) is discussed. As the result of surface potential effect, direct comparison of 0.3×150-μm² gate devices yielded improved gate breakdown characteristics and a DC output conductance of less than 15 mS/mm for the surface undoped structure compared to 50 mS/mm for the doped structure. The surface undoped MEMT achieved a very high maximum stable gain of 19.2 dB compared to 16.0 dB for the surface doped HEMT at 18 GHz, largely due to the improved g_m/g ₀ ratio. This study demonstrates that control of the surface potential in In_0.52Al_0.48As-In_0.53Ga _0.47As-InP HEMTs is consistent with the effect of a gate recess in MESFETs. This study also shows that, in achieving high-gain applications of HEMTs, the surface potential near the gate edge should be optimized through unconventional surface layer design     

Electro-optic sampling measurement of coplanar waveguide (coupled slot line) modes

The application of the electro-optic sampling technique for the characterisation of propagating modes of planar guiding structures on GaAs is described. The characteristics of even and odd modes of coplanar waveguide on semi-insulating GaAs substrate are investigated. The guide wavelength for each mode is directly obtained from standing wave measurements by electro-optic sampling, and compared to the theoretical values.     

Characterization of surface-undoped In0.52Al0.48As/In0.53Ga0.47As/InP high electron mobilitytransistors

High-performance 0.3-μm-gate-length surface-undoped In_0.52 Al_0.48As/In_0.53Ga_0.47As/InP high-electron-mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) have been characterized and compared with a surface-doped structure. At 18 GHz, the surface-undoped HEMT has achieved a maximum stable gain (MSG) of 19.2 dB compared to 16.0 dB for the surface-doped structure. The higher MSG value of the surface-undoped HEMTs is obtained due to the improved g_m/g₀ ratio associated with the surface-induced electric field spreading effect. Comparison of identical 0.3-×150-μm-gate devices fabricated on surface-undoped and -doped structures has shown greatly improved gate leakage characteristics and much lower output conductance for the surface-undoped structure. It is demonstrated that the surface potential, modulated by different surface layer designs, affects the charge control in the conducting channel, especially the carrier injection into the buffer, resulting in excess output conductance. Several millimeter-wave coplanar waveguide (CPW) monolithic distributed amplifiers have been successfully fabricated by using the surface-undoped HEMT structure. A high gain per stage distributed amplifier with 170-dB±1-dB small-signal gain across a frequency band of 24-40 GHz, a W-band monolithic integrated circuit with 6.4-dB gain at 94 GHz, and a broad bandwidth distributed amplifier with 5-dB gain across a frequency band of 5 to 100 GHz have been demonstrated by using the surface-undoped structures     

Triple-channel InP-based HEMT with highly nonlinear transconductance for nonlinear circuit applications

The authors report the development of a triple-channel HEMT with two undoped In/sub 0.53/Ga/sub 0.47/As layers and a spike-doped In/sub 0.52/Al/sub 0.48/As layer on InP, designed to have a strongly nonlinear transconductance. The effective electron velocity and the electron density in the InGaAs layers are higher than in the thick InAlAs layer resulting in a highly nonlinear transconductance device with the potential for improved performance in nonlinear microwave circuit applications, as compared with conventional MESFETs and HEMTs.<>     

Millimetre-wave active probe frequency-multiplier for on-wafer characterisation of GaAs devices and ICs

A millimetre-wave active probe quintupler with an output frequency range of 60 to 100 GHz has been developed. The frequency multiplier circuit was implemented in a coplanar waveguide. Using this probe along with the electro-optic sampling technique, on-wafer millimetre-wave vector measurement up to 100 GHz and time-waveform measurement at 77 GHz of test structures on a GaAs substrate have been demonstrated.<>     

94 GHz InP MMIC five-section distributed amplifier

A single-stage 94 GHz InP MMIC amplifier with 6.4 dB gain at 94 GHz has been developed, which is the highest-frequency MMIC amplifier reported to date. Lattice-matched GaInAs/AlInAs HEMTs with 0.1 mu m mushroom gates were the active devices. The CPW MMIC chip dimensions are 500 mu m*670 mu m.<>     

100-GHz high-gain InP MMIC cascode amplifier

A high-gain InP monolithic millimeter-wave integrated circuit (MMIC) cascode amplifier has been developed which has 8.0 dB of average gain from 75 to 100 GHz when biased for maximum bandwidth, and more than 12 dB of gain at 80 GHz at the maximum-gain bias point, representing the highest gains reported to date, obtained from MMICs at W band (75-100 GHz). Lattice-matched InGaAs-InAlAs high-electron-mobility-transistors (HEMTs) with 0.1-μm gates were the active devices. A coplanar waveguide (CPW) was the transmission medium for this MMIC with an overall chip dimension of 600×500 μm     

100 GHz active electronic probe for on-wafer S-parameter measurements

Reports the development of an active electronic probe for 100 GHz on-wafer S-parameter measurements. Integrated on the substrate of this wafer probe were a quintupler for 100 GHz stimulus signal generation, two directional couplers for incident and reflected signals sampling, and two newly developed harmonic mixers to down-convert these 100 GHz signals to 20 MHz. The authors also demonstrate all-electronic on-wafer 75-100 GHz two-port S-parameter measurements using these probes.<>     

Single-mode operation of coplanar waveguides

A grounded coplanar waveguide structure with finite-size ground planes is analysed as three coupled microstrip lines. The three normal propagation modes of this structure are examined for various geometries, and some physical layout guidelines are established.