Composite Channel High Electron Mobility Transistors Research Articles

Composite channel 100 nm InP HEMT with ultrathin barrier for millimetre wave applications

This study introduces a High Electron Mobility Transistor (HEMT) designed for millimeter-wave applications, utilizing a composite channel structure based on InP and InGaAs-InAs-InGaAs. The proposed device incorporates an ultra-thin 2 nm barsrier layer, a distinctive composite channel topology, and a judicious selection of III-V materials. These features collectively contribute to an improved confinement of electrons within the channel, thereby improving the concentration of two-dimensional electron gas (2DEG), and consequently, enhancing the mobility and speed of the device. The proposed device exhibits a unity current gain frequency (f T) of 249 GHz and a maximum oscillation frequency (f MAX) of 523.9 GHz, accompanied by a current gain of 67.7 dB at 0.1 GHz. The off-state leakage current is maintained within the nanoampere range, and the minimum noise figure (NF MIN) is merely 0.76 dB at 10 GHz. A comparative analysis of DC and RF performance, along with an examination of associated parasitic elements, is conducted among various composite channel HEMTs proposed in recent literature. A quantitative justification is provided for the superiority of InGaAs-InAs-InGaAs channel HEMTs, establishing their heightened f T and f MAX. The proposed InGaAs-InAs-InGaAs channel HEMTs exhibit 1.4 times improved f T and f MAX, coupled with only half the NF MIN in comparison to their InGaAs-InP-InGaAs channel counterparts. To further comprehend the device’s behavior under varying RF conditions, a frequency-dependent intrinsic Field-Effect Transistor (FET) model is presented. This model facilitates the analysis of the device’s performance and allows the identification of the impact of individual parameters on the overall system.

Investigation on Effect of Doped InP Subchannel Thickness and Delta-Doped InP Layer of Composite Channel HEMT

DC performances of a depletion-mode 100-nm In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As/InP composite channel InP-based high-electron-mobility transistor (HEMT) is investigated by using numerical simulation. The transfer, output, and breakdown characteristics of different doped InP subchannel thickness In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As/InP composite channel HEMT are compared. Decreasing the thickness of the doped InP subchannel from 10 to 5 nm results in a decline of the output current. However, the threshold voltage is increased from −0.77 to −0.6 V and the breakdown voltage is improved from 1.99 to 5.69 V at bias of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{{\mathrm {gs}}}-{V}_{{\mathrm {t}}} = -0.5$ </tex-math></inline-formula> V. To enhance the breakdown characteristic of In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As/InP composite channel HEMT, we minimize the thickness of the doped InP layer and replace the doped InP layer with the delta-doped layer. The structure is compared with the conventional double delta-doped structure in the performance of transfer, output, and breakdown characteristics. At ON-state, the electrons of two kinds of structure concentrate in the InGaAs channel. The output current and the threshold voltage of the composite channel structure are at the same level compared with the conventional double delta-doped structure. However, at OFF-state, because of the transfer of electrons into the InP subchannel, part of electric potential will not be concentrated at the drain side of the gate region but distributed in other area of the channel. A higher drain voltage is required to achieve electric field strength enough to breakdown and the breakdown voltage is improved obviously.

Comparative assessment of InGaAs sub-channel and InAs composite channel double gate (DG)-HEMT for sub-millimeter wave applications

This work analyses the impact of channel material, channel thickness (TCH) and gate length (Lg) on the various performance device metrics of Double-gate (DG) High Electron Mobility Transistor (HEMT) by using 2D Sentaurus TCAD simulation. A comparison between In0.53Ga0.47As/In0.7Ga0.3As/In0.53Ga0.47As sub-channel and In0.7Ga0.3As/InAs/In0.7Ga0.3As composite channel DG-HEMT along with SG-HEMT is made by characterizing the device with structural and geometrical parameters suitable for applications requiring high frequency operations. The DG-In0.53Ga0.7As/In0.7Ga0.3As/In0.53Ga0.7As sub-channel/DG-In0.7Ga0.3As/InAs/In0.7Ga0.3As composite channel HEMT with channel thickness of 13 nm and barrier thickness (TB) of 2 nm with Lg = 30 nm are seen offering a positive threshold voltage (VT) of 0.298/0.21 V, transconductance (gm) of 3.09/3.3 mS/µm, with cut-off frequency (fT) and maximum oscillation frequency (fmax) of 776/788 GHz and 905/978 GHz, respectively at Vds = 0.5 V is obtained. If the channel thickness of the DG-InAs composite channel device is scaled and reduced to 10 nm, the RF performances are further enhanced to 809 GHz (fT) and 1030 GHz (fmax). Compared to DG-InGaAs sub-channel device, the device with thin DG-InAs composite channel device shows a better performance in terms of drain current (Ids), analog/RF performance thereby making it preferable for future THz applications.

Fabrication of 45 nm high In component metamorphic In 0.7 Ga 0.3 As/In 0.6 Ga 0.4 As composite‐channel high electron‐mobility transistors on GaAs substrates

A 45 nm high In component metamorphic In0.7Ga0.3As/In0.6Ga0.4As composite-channel high electron-mobility transistor (mHEMT) on GaAs substrate with good DC and RF performance has been developed. The structure was grown by molecular beam epitaxy and exhibits a superior electron mobility of 10200 cm2/(V.s) and a sheet density of 3.5 × 1012 cm−2 at a room temperature. A combined optical and e-beam lithography technology was used to achieve the nanometre mHEMT device. The mHEMT device shows an extrinsic transconductance of up to 990 mS/mm and a maximum current density of 910 mA/mm. The unity current gain cutoff frequency fT and the maximum oscillation frequency f max are 187.94 and 258.62 GHz, respectively. These performances make the device well suited for millimetre-wave applications.

Al Ga As ∕ Ga As high-electron mobility transistor with In0.1Ga0.9As∕In0.22Ga0.78As∕In0.1Ga0.9As channel grown by metal-organic chemical vapor deposition

A composite-channel high-electron mobility transistor (HEMT) on GaAs substrate is designed and fabricated, using the following methodology to improve device performance: (1) an AlGaAs buffer layer, (2) an AlGaAs∕GaAs superlattice layer, and (3) an In0.1Ga0.9As∕In0.22Ga0.78As∕In0.1Ga0.9As composite channel. For comparison, a control HEMT without the composite channel is fabricated in parallel (whose channel comprises only a 125-Å-thick In0.22Ga0.78As layer). These two devices are grown by metal-organic chemical vapor deposition. The peak extrinsic transconductance (gm,ext) of the control HEMT with a gate length of 1μm is 160mS∕mm, while the peak gm,ext of the composite-channel HEMT of the identical gate length is measured to be 186mS∕mm. The on-state breakdown voltage of the composite-channel HEMT is as great as 9.7V, which represents an improvement of 1.4V over the control HEMT. The control HEMT exhibits a current gain cutoff frequency (fT) of 12.5GHz and a maximum frequency of oscillation (fmax) of 31.5GHz, while the composite-channel HEMT exhibits an fT of 16.9GHz and an fmax of 37.4GHz. Experimental data reveal that the composite-channel structure provides improved gate-to-source voltage swing, improved saturation current density, enhanced fT, enhanced fmax, and enhanced breakdown voltage without compromising electron mobility. The composite-channel HEMT is thus far superior to the control HEMT and is highly promising for use in high-frequency applications.

High-Performance InGaAs/InP Composite-Channel High Electron Mobility Transistors Grown by Metal–Organic Vapor-Phase Epitaxy

This paper reports InGaAs/InP composite-channel (CC) high electron mobility transistors (HEMTs) grown by metal–organic vapor-phase epitaxy (MOVPE) with excellent breakdown and high-speed characteristics. Atomic force microscopy (AFM) reveals high-quality heterointerfaces between In(Ga,Al)As and In(Al)P. Fabricated 80-nm-gate CC HEMTs exhibit on- and off-state breakdown (burnout) voltages estimated at higher than 3 and 8 V. An excellent current-gain cutoff frequency ( fT) of 186 GHz is also obtained in the CC HEMTs. The on-wafer uniformity of CC-HEMT characteristics is comparable to those of our mature 100-nm-gate InGaAs single-channel HEMTs. Bias-stress aging tests reveals that the lifetime of CC HEMTs is expected to be comparable to that of our conventional InGaAs single-channel HEMTs.

RF and Logic Performance Improvement of $ \hbox{In}_{0.7}\hbox{Ga}_{0.3}\hbox{As}/\hbox{InAs}/\hbox{In}_{0.7}\hbox{Ga}_{0.3}\hbox{As}$ Composite-Channel HEMT Using Gate-Sinking Technology

Eighty-nanometer-gate In0.7Ga0.3As/InAs/In0.7Ga0.3As composite-channel high-electron mobility transistors (HEMTs), which are fabricated using platinum buried gate as the Schottky contact metal, were evaluated for RF and logic application. After gate sinking at 250degC for 3 min, the device exhibited a high gm value of 1590 mS/mm at Vd = 0.5 V, the current-gain cutoff frequency fT was increased from 390 to 494 GHz, and the gate-delay time was decreased from 0.83 to 0.78 ps at supply voltage of 0.6 V. This is the highest fT achieved for 80-nm-gate-length HEMT devices. These superior performances are attributed to the reduction of distance between gate and channel and the reduction of parasitic gate capacitances during the gate-sinking process. Moreover, such superior performances were achieved through a very simple and straightforward fabrication process with optimal epistructure of the device.

Research of breakdown characteristic of InP composite channel HEMT

Density gradient quantum model has been used to analyse the breakdown characteristic of InP-based composite channel HEMT(high electron mobility transistor). The collision ionization in composite channel and quantum effect has been taken into consideration. We payed great attention to the relationship of on-state breakdown voltage with respect to the thickness of In0.7Ga0.3As channel, and promoted a method to enhance the on-state breakdown voltage. A commercial 2D-device simulation program. Sentaurus has been used to simulate the on-state breakdown voltage of the device. A comparison has been made between the result of simulated and measured data. The result shows that with the reduction of the thickness of In0.7Ga0.3As channel, on-state breakdown voltage of the device will be enhanced greatly without reducing saturation current, which has a significant meaning for promoting the power performance of InP-based HEMT.

In 0.53 Ga 0.47 As/InAs 0.3 P 0.7 composite channel high electron mobility transistors

An In0.53Ga0.47As/InAs0.3P0.7 composite channel high electron mobility transistor (HEMT) structure was grown by molecular beam epitaxy. Room-temperature Hall measurement showed that the device wafer had an electron mobility of 7300 cm2/V s and a sheet electron density of 3×1012 cm−2. The fabricated HEMT devices with a gate length of 0.25 µm exhibited excellent DC and microwave performance with a peak extrinsic transconductance of 888.3 mS/mm, a cutoff frequency (fT) of 115 GHz, and a maximum frequency of oscillation of 137 GHz. This is believed to be the first report of InGaAs/InAsP composite channel HEMTs. The fT is the highest ever reported for any composite channel HEMTs with the same gate length.

On-state and off-state breakdown in GaInAs/InP composite-channel HEMT's with variable GaInAs channel thickness

Short-channel Ga/sub 0.47/In/sub 0.53/As high electron mobility transistors (HEMTs) suffer from low breakdown voltages due to enhanced impact-ionization effects in the narrow bandgap channel. This could limit the application of single-channel devices to medium power millimeter-wave systems. A composite Ga/sub 0.47/In/sub 0.53/As/InP channel, which exploits the high electron mobility of Ga/sub 0.47/In/sub 0.53/As at low electric fields, and the low impact-ionization and high electron saturation velocity of InP at high electric fields can overcome this limitation. In this paper we study on-state and off-state breakdown of Ga/sub 0.47/In/sub 0.53/As/InP composite-channel HEMT's with a variable GaInAs channel thickness of 30, 50, and 100 /spl Aring/. Reduction of channel thickness leads to the improvement of both on-state and off-state breakdown voltages. In on-state conditions, the enhancement in the effective Ga/sub 0.47/In/sub 0.53/As channel bandgap that takes place when the channel thickness is reduced to the order of the de Broglie wavelength (channel quantization) effectively enhances the threshold energy for impact-ionization, which is further reduced by real space transfer of electrons from the Ga/sub 0.47/In/sub 0.53/As into the wider bandgap InP. Channel thickness reduction also causes a decrease in the sheet carrier concentration in the extrinsic gate-drain region and therefore, a reduction of the electric field beneath the gate. This, together with the adoption of an Al/sub 0.6/In/sub 0.4/As Schottky layer (increasing the gate Schottky barrier height), leads to excellent values of the gate-drain breakdown voltage. In conclusion, composite channel InAlAs/GaInAs/InP HEMTs, thanks to the combined effect of effective band-gap increase, enhanced real space transfer into InP, and sheet carrier density reduction, allow a good trade-off between current driving capability and both on-state and off-state breakdown voltage.