Metamorphic InAlAs/InGaAs HEMTs on GaAs substrates with a novelcomposite channels design

We report on fabrication and performance of novel 0.13 μm T-gate metamorphic InAlAs/InGaAs HEMTs on GaAs substrates with composite InGaAs channels, combining the superior transport properties of In_0.52Ga_0.48As with low-impact ionization in the In_0.32Ga_0.68As subchannel. These devices exhibit excellent DC characteristics, high drain currents of 750 mA/mm, extrinsic transconductances of 600 mS/mm, combined with still very low output conductance values of 20 mS/mm, and high channel and gate breakdown voltages. The use of a composite InGaAs channels leads to excellent cut-off frequencies: f_max of 350 GHz and an f_T 160 GHz at V_DS=1.5 V. These are the best microwave frequency results ever reported for any FET on GaAs substrate     

Metamorphic modulation-doped InAlAs/InGaAs/InAlAs heterostructures with high electron mobility grown on gaas substrates

Metamorphic modulation-doped InGaAs/InAlAs heterostructures have been MBE-grown on GaAs substrates. The optimization of low-temperature growth conditions for a graded-composition buffer layer made it possible to reduce the amount of structural defects in the active layers of the structure. The electron mobility in the 2D channel of metamorphic structures grown under optimum conditions (8100 cm²/V s at 300 K) noticeably exceeds the values achievable in strained InGaAs/AlGaAs heterostructures on GaAs substrates.     

High-performance InAlAs/InGaAs HEMTs and MESFETs

The fabrication and microwave performance of heterostructure InAlAs/InGaAs HEMTs (high-electron-mobility transistors) and MESFETs are described. Maximum stable gains of 14.3 dB for a HEMT and 12 dB for a MESFET at 26.5 GHz have been achieved. These are believed to be record gains for FETs having gates as long as 0.7 μm     

Striped-channel InAlAs/InGaAs HEMTs with shallow-grating structures

Striped-channel (SC) InAlAs/InGaAs HEMTs have been demonstrated with shallow gratings. The shallow grating structure keeps the gate from touching the channel layer and thus solves the gate leakage problem observed in the deep grating devices on InP substrates. Various channel widths have been realized to study the impact of the channel width on the dc and microwave performance. Due to the enhanced charge control in the SC HEMTs, enhanced transconductance/source-drain current (G_m /I_ds) and transconductance/output conductance (G_m /G_ds) were observed. Compared with conventional HEMTs, the SC HEMTs showed degraded f_T due to additional parasitic capacitances and improved f_max due to better carrier confinement     

50-nm T-Gate InAlAs/InGaAs Metamorphic HEMTs With Low Noise and High fT Characteristics

We report 50-nm T-gate metamorphic high-electron mobility transistors (MHEMTs) with low noise figure and high characteristics. The 30 mumtimes2 MHEMT shows a drain current density of 690 mA/mm, a g_m,max of 1270 mS/mm, an f_T of 489 GHz, and an of 422 GHz. In the frequency range of 59-61 GHz, the noise figure is less than 0.7 dB, and the associated gain was greater than 9 dB at a drain voltage of 1.3 V and a gate voltage of -0.8 V. To our knowledge, the MHEMT shows the best performance in terms of and noise figure among GaAs-based HEMTs.     

Electroluminescence of InAlAs/InGaAs HEMTs lattice-matched to InPsubstrates

Electroluminescence (EL) due to the electron-hole recombination in the channel of InAlAs/InGaAs HEMTs lattice-matched to InP substrates has been measured at room temperature. The carrier temperature extracted from the obtained spectra has been found to be approximately 300 K. It has also been found that the EL comes from a region between the source and the gate by measuring its spatial distribution. These two features imply that holes generated at the drain edge in the channel due to the impact ionization pile up and recombine with the majority electrons between the source and the gate, and agree with results of theoretical analysis     

栅长90nm的晶格匹配InAlAs／InGaAs／InP HEMT

文章报道了90nm栅长的晶格匹配InP基HEMT器件。栅图形是通过80kV的电子束直写的,并采用了优化的三层胶工艺。器件做在匹配的InAlAs／InGaAs／InP HEMT材料上。当Vds=1．0V时,两指75μm栅宽器件的本征峰值跨导达到720ms／mm,最大电流密度为500mA／mm,器件的阂值电压为．0．8V,截止频率达到127GHz,最大振荡频率达到152GHz。     

Ultrahigh-speed pseudomorphic InGaAs/InAlAs HEMTs with 400-GHzcutoff frequency

An excellent cutoff frequency (f_t) as high as 400 GHz was successfully realized in 45-nm-gate pseudomorphic InGaAs/InAlAs high electron mobility transistors (HEMTs). An additional vertical gate-recess suppressed short-channel effects, while keeping good pinchoff characteristics. Gate length (L_g) dependence of electron transit time (τ_transit) implied an increased saturation velocity (υ_s) of 3.6×10⁷ cm/s in the developed pseudomorphic HEMTs. This f_t is the highest value ever reported for any transistors to date     

30-nm two-step recess gate InP-Based InAlAs/InGaAs HEMTs

Two-step recess gate technology has been developed for sub-100-nm gate InP-based InAlAs/InGaAs high-electron mobility transistors (HEMTs). This gate structure is found to be advantageous for the preciseness of the metallurgical gate length as well as a comparable stability to the conventional gate structure with an InP etch stop layer. The two-step recess gate is optimized focusing on the lateral width of the gate recess. Due to the stability of the gate recess with an InP surface, a laterally wide gate recess gives the maximum cutoff frequency, lower gate leakage current, smaller output conductance and higher maximum frequency of oscillation. Finally, the uniformity of the device characteristics evaluated for sub-100-nm HEMTs with the optimized recess width. The result reveals the significant role of the short channel effects on the device uniformity.     

0.3-μm gate-length enhancement mode InAlAs/InGaAs/InPhigh-electron mobility transistor

The fabrication and performance of ultra-high-speed 0.3-μm gate-length enhancement-mode high-electron-mobility transistors (E-HEMT's) are reported. By using a buried platinum-gate technology and incorporating an etch-stop layer in the heterostructure design, submicron E-HEMT devices exhibiting both high-threshold voltages and excellent threshold voltage uniformity have been achieved. The devices demonstrate a threshold voltage of +171 mV with a standard deviation of only 9 mV. In addition, a maximum DC extrinsic transconductance of 697 mS/mm is measured at room temperature. The output conductance is 22 mS/mm, which results in a maximum voltage gain (g_m/g₀ ) of 32. The devices show excellent RF performance, with a unity current-gain cutoff frequency (f_t) of 116 GHz and a maximum frequency of oscillation (f_max) of 229 GHz. To the best of the authors' knowledge, these are the highest reported frequencies for lattice-matched E-HEMT's on InP     

Bias-stress-induced increase in parasitic resistance of InP-based InAlAs/InGaAs HEMTs

The reliability of InP-based HEMTs is studied, focussing on how it is affected by the doped layer material and gate recess structure. Bias-and-temperature stress tests reveal that fluorine-induced donor passivation in the recess region, formed adjacent to the gate electrode, causes the source resistance (R_s) to increase at large drain bias voltages. The increase in R_s can be prevented by using InP or InAlP as the carrier supply layer material instead of InAlAs. On the other hand, the increase in the drain resistance (R_d) does not depend on the material of the carrier supply layer, which suggests that a mechanism different from that in the case of R_s should be considered. It is also found that a deep gate recess suppresses the increase in R_d after long-term stressing.     

Very high gain millimeter-wave InAlAs/InGaAs/GaAs metamorphicHEMT's

We report the first demonstration of W-band metamorphic HEMTs/LNA MMICs using an AlGaAsSb lattice strain relief buffer layer on a GaAs substrate. 0.1×50 μm low-noise devices have shown typical extrinsic transconductance of 850 mS/mm with high maximum drain current of 700 mA/mm and gate-drain breakdown voltage of 4.5 V. Small-signal S-parameter measurements performed on the 0.1-μm devices exhibited an excellent f_T of 225 GHz and maximum stable gain (MSG) of 12.9 dB at 60 GHz and 10.4 dB at 110 GHz. The three-stage W-band LNA MMIC exhibits 4.2 dB noise figure with 18 dB gain at 82 GHz and 4.8 dB noise figure with 14 dB gain at 89 GHz, The gain and noise performance of the metamorphic HEMT technology is very close to that of the InP-based HEMT     

W-band low-noise InAlAs/InGaAs lattice-matched HEMTs

Very low-noise 0.15-μm gate-length W-band In_0.52 Al_0.48As/In_0.53Ga_0.47As/In _0.52Al_0.48As/InP lattice-matched HEMTs are discussed. A maximum extrinsic transconductance of 1300 mS/mm has been measured for the device. At 18 GHz, a noise figure of 0.3 dB with an associated gain of 17.2 dB was measured. The device also exhibited a minimum noise figure of 1.4 dB with 6.6-dB associated gain at 93 GHz. A maximum available gain of 12.6 dB at 95 GHz, corresponding to a maximum frequency of oscillation, f_max, of 405 GHz (-6-dB/octave extrapolation) in the device was measured. These are the best device results yet reported. These results clearly demonstrate the potential of the InP-based HEMTs for low-noise applications, at least up to 100 GHz     

Metamorphic AlInAs/GaInAs HEMTs on GaAs Substrates by MOCVD

Metamorphic AlInAs/GaInAs high-electron mobility transistors with very good device performance have been grown by metal-organic chemical vapor deposition (MOCVD), with the introduction of an effective multistage buffering scheme. Measured room-temperature Hall mobilities of the 2-DEG were over 8000 cm²/V ldr s with sheet carrier densities larger than 4 times 10¹² cm^-2. Transistors with 1-mum gate length exhibited transconductance up to 626 mS/mm. The unity current gain cutoff frequency f_T and the maximum oscillation frequency f_max were 39.1 and 71 GHz, respectively. These results are very encouraging toward the manufacturing of metamorphic devices on GaAs substrates by MOCVD.     

Extremely high gain 0.15 mu m gate-length InAlAs/InGaAs/InP HEMTs

High electron mobility transistors (HEMTs) based on the InAlAs/InGaAs heterojunction grown lattice matched to InP were fabricated with 0.15 mu m T-shaped gates. The use of an undoped InGaAs cap layer in the epitaxial structure leads to excellent gate characteristics and very high transistor gain. At 95 GHz, a maximum available gain of 13.6 dB was measured. A maximum frequency of oscillation f/sub max/ of 455 GHz was obtained by extrapolating from 95 GHz at -6 dB/octave. This is the best reported gain performance for any transistor.<>     

An 80-Gbit/s multiplexer IC using InAlAs/InGaAs/InP HEMTs

This paper describes the design and performance of an 80-Gbit/s 2:1 selector-type multiplexer IC fabricated with InAlAs/InGaAs/InP HEMTs. By using a double-layer interconnection process with a low-dielectric insulator, microstrip lines were designed to make impedance-matched, high-speed intercell connection of critical signal paths. The record operating data rate was measured on a 3-in wafer. In spite of the bandwidth limitation on the measurement setup, clear eye patterns were successfully observed for the first time. The obtained circuit speed improvement from the previous result of 64 Gbit/s owes much to this high-speed interconnection design     

A physical model for the kink effect in InAlAs/InGaAs HEMTs

We present a new model for the the kink effect in InAlAs/InGaAs HEMTs. The model suggests that the kink is due to a threshold voltage shift which arises from a hole pile-up in the extrinsic source and an ensuing charging of the surface and/or the buffer-substrate interface. The model captures many of the observed behaviors of the kink, including the kink's dependence on bias, time, temperature, illumination, and device structure. Using the model, we have developed a simple equivalent circuit, which reproduced well the kink's dc characteristics, its time evolution in the nanosecond range, and its dependence on illumination     

InAlAs/InGaAs/InP HEMTs with high breakdown voltages using double-recess gate process

The DC and RF performance of InAlAs/InGaAs/InP HEMTs fabricated using a double-recess gate process are reported. A gate-drain breakdown voltage as high as 16 V was observed. The HEMTs also exhibited a high source-drain breakdown voltage near pinchoff of 16 V and a low RF output conductance of 6 mS/mm. For a 1.4 mu m gate length, an intrinsic transconductance of 560 mS/mm and f/sub T/ and f/sub max/ values of 16 and 40 GHz, respectively, were achieved.<>     

11 GHz ultrawide-bandwidth monolithic photoreceiver using InGaAspin PD and InAlAs/InGaAs HEMTs

A very-wide-bandwidth long-wavelength monolithically integrated photoreceiver is presented which comprises an InGaAs pin PD and a transimpedance amplifier. The receiver uses epilayers grown by one-step MOVPE. The InGaAs channel high-electron-mobility field effect transistor (HEMT) employs an Si planar-doped carrier supplying layer to obtain larger transconductance and uniform threshold voltage. The 0.5 μm gate length is used for HEMTs to enhance the speed of operation. This receiver shows a very wide bandwidth of 11 GHz, and opened eye for a 15 Gbit/s NRZ signal. This is the first demonstration of a long-wavelength monolithic photoreceiver receiving a 15 Gbit/s light signal