• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.30 no.4
• /
• pp.282-285
• /
• 2019

A 100-nm gate-length metamorphic high electron mobility transistor(mHEMT) with a T-shaped gate was fabricated using a two-step gate recess and characterized for DC and microwave performance. The mHEMT device exhibited DC output characteristics having drain current($I_{dss}$), an extrinsic transconductance($g_m$) of 1,090 mS/mm and a threshold voltage($V_{th}$) of -0.65 V. The $f_T$ and $f_{max}$ obtained for the 100-nm mHEMT device were 190 and 260 GHz, respectively. The developed mHEMT will be applied in fabricating W-band monolithic microwave integrated circuits(MMICs).

• Journal of the Korea Institute of Military Science and Technology
• /
• v.12 no.4
• /
• pp.483-490
• /
• 2009

In this paper, a novel low-damage silicon nitride passivation for 100nm InAlAs/InGaAs MHEMTs has been developed using remote ICPCVD. The silicon nitride deposited by ICPCVD showed higher quality, higher density, and lower hydrogen concentration than those of silicon nitride deposited by PECVD. In particular, we successfully minimized the plasma damage by separating the silicon nitride deposition region remotely from ICP generation region, typically with distance of 34cm. The silicon nitride passivation with remote ICPCVD has been successfully demonstrated on GaAs MHEMTs with minimized damage. The passivated devices showed considerable improvement in DC characteristics and also exhibited excellent RF characteristics($f_T$of 200GHz).The devices with remote ICPCVD passivation of 50nm silicon nitride exhibited 22% improvement(535mS/mm to 654mS/mm) of a maximum extrinsic transconductance($g_{m.max}$) and 20% improvement(551mA/mm to 662mA/mm) of a maximum saturation drain current ($I_{DS.max}$) compared to those of unpassivated ones, respectively. The results achieved in this work demonstrate that remote ICPCVD is a suitable candidate for the next-generation MHEMT passivation technique.

• Proceedings of the IEEK Conference
• /
• 2006.06a
• /
• pp.553-554
• /
• 2006

In this paper, 77 GHz CPW power amplifier MMIC, which are consisted of a 2 stage driver stage and a power stage employing $8{\times}50um$ gate width, have been successfully developed by using 120nm $In_{0.4}AlAs/In_{0.35}GaAs$ Metamorphic high electron mobility transistors (MHEMTs). The devices show an extrinsic transconductance $g_m$ of 660 mS/mm, a maximum drain current of 700 mA/mm, and a gate drain breakdown voltage of -8.5 V. A cut-off frequency ($f_T$) of 172 GHz and a maximum oscillation frequency ($f_{max}$) of over 300 GHz are achieved. The fabricated PA exhibited high power gain of 20dB only with 3 stages. The output power is measured to be 12.5 dBm.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.12
• /
• pp.7-12
• /
• 2004

In this paper, CPW wideband distributed amplifier was designed and fabricated using 0.1 $\mum$ InGaAs/InAlAs/GaAs Metamorphic HEMT(High Electron Mobility Transistor). The DC characteristics of MHEMT are 442 mA/mm of drain current density, 409 mS/mm of maximum transconductance. The current gain cut-off frequency(fT) is 140 GHz and the maximum oscillation frequency(fmax) is 447 GHz. The distributed amplifier was designed using 0.1 $\mum$ MHEMT and CPW technology. We designed the structure of CPW curve, tee and cross to analyze the discontinuity characteristics of the CPW line. The MIMIC circuit patterns were optimized electromagnetic field through momentum. The designed distributed amplifier was fabricated using our MIMIC standard process. The measured results show S21 gain of above 6 dB from DC to 45 GHz. Input reflection coefficient S11 of -10 dB, and output reflection coefficient S22 of -7 dB at 45 GHz, respectively. The chip size of the fabricated CPW distributed amplifier is 2.0 mm$\times$l.2 mm.

• Journal of the Semiconductor & Display Technology
• /
• v.10 no.1
• /
• pp.63-73
• /
• 2011

Metamorphic HEMTs (MHEMTs) have emerged as excellent challenges for the design and fabrication of high-speed HEMTs for millimeter-wave applications. Some of improvements result from improved mobility and larger conduction band discontinuity in the channel, leading to more efficient modulation doping, better confinement, and better device performance compared with conventional pseudomorphic HEMTs (PHEMTs). For the optimized device design and development, we have performed the calibration on the DC characteristics of our fabricated 0.1 ${\mu}m$ ${\Gamma}$-gate MHEMT device having the modulation-doped $In_{0.52}Al_{0.48}As/In_{0.53}Ga_{0.47}$As heterostructure on the GaAs wafer using the hydrodynamic transport model of a commercial 2D ISE-DESSIS device simulator. The well-calibrated device simulation shows very good agreement with the DC characteristic of the 0.1 ${\mu}m$ ${\Gamma}$-gate MHEMT device. We expect that our calibration result can help design over-100-GHz MHEMT devices for better device performance.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.48 no.11
• /
• pp.1-8
• /
• 2011

One of the most important parameters that limit maximum output power of transistor is breakdown. InAlAs/InGaAs/GaAs Metamorphic HEMTs (MHEMTs) have some advantages, especially for cost, compared with InP-based ones. However, GaAs-based MHEMTs and InP-based HEMTs are limited by lower breakdown voltage for output power even though they have good microwave and millimeter-wave frequency performance with lower minimum noise figure. In this paper, InAlAs/$In_xGa_{1-x}As$/GaAs MHEMTs are simulated and analyzed for breakdown. The parameters affecting breakdown are investigated in the fabricated 0.1-${\mu}m$ ${\Gamma}$-gate MHEMT device having the modulation-doped $In_{0.52}Al_{0.48}As/In_{0.53}Ga_{0.47}As$ heterostructure on the GaAs wafer using the hydrodynamic transport model of a 2D commercial device simulator. The impact ionization and gate field effect in the fabricated device including deep-level traps are analyzed for breakdown. In addition, Indium mole-fraction-dependent impact ionization rates are proposed empirically for $In_{0.52}Al_{0.48}As/In_xGa_{1-x}As$/GaAs MHEMTs.

• Proceedings of the IEEK Conference
• /
• 2006.06a
• /
• pp.471-472
• /
• 2006

The passivation technology is very important, because this technology can protect a device against the influence of ambient environment, and prevent the performance reduction. In this paper, we fabricated the $0.1{\mu}m\;{\Gamma}$-gate InAlAs/InGaAs metamorphic high electron mobility transistors (MHEMTs) on GaAs substrates using the low-k benzocyclobutene (BCB) and $Si_3N_4$ as a passivation and we performed the comparisons of characteristics of the MHEMTs. After passivation, the DC and RF measurement results were decreased either the conventional Si3N4 or BCB layers. The decrement of the BCB passivation was smaller than the $Si_3N_4$ passivation.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.44 no.4
• /
• pp.80-85
• /
• 2007

The passivation is one of the important technologies for protection of the devies from damage. In this paper, we fabricated $0.1{\mu}m\;{\Gamma}$--gate InAIAs/InGaAs metamorphic high electron mobility transistors (MHEMTs) on a GaAs substrate. And then the wafer with MHEMTs was divided into two pieces; one for passivation and another for without passivation experiments. The passivations were done by using both low-k BCB and Si3N4 thin films. DC and RF performances were measured and the results are compared. The MHEMTs with BCB passivation show lower degradation than ones with Si3N4 passivation.

• Journal of the Semiconductor & Display Technology
• /
• v.10 no.4
• /
• pp.107-112
• /
• 2011

This paper is for improving the RF frequency performance of a fabricated 100nm ${\Gamma}$-gate MHEMT, scaling down vertically for the epitaxy-structure layers of the device. Hydrodynamic simulation parameters are calibrated for the fabricated MHEMT with the modulation-doped $In_{0.52}Al_{0.48}As/In_{0.53}Ga_{0.47}$As heterostructure grown on the GaAs substrate. With these calibrated parameters, simulations for the vertically-scaled epitaxial layers of the device are performed and analyzed for DC/RF characteristics, including the quantization effect due to the thickness reduction of InGaAs channel layer. A newly designed epitaxy-structure device shows higher extrinsic transconductance, $g_m$ of 1.556 S/mm, and higher frequency performance, $f_T$ of 222.5 GHz and $f_{max}$ of 849.6 GHz.

• Journal of the Korean Vacuum Society
• /
• v.22 no.6
• /
• pp.335-340
• /
• 2013

This paper is for the simulation design to enhance the breakdown voltage of MHEMTs with an InP-etchstop layer. Gate-recess and channel structures has been simulated and analyzed for the breakdown of the MHEMT devices. The fully removed recess structure at the drain side of MHEMT shows that the breakdown voltage enhances from 2 V to almost 4 V as the saturation current at gate voltage of 0 V is reduced from 90 mA to 60 mA at drain voltage of 2 V. This is because the electron-captured negatively fixed charges at the drain-side interface between the InAlAs barrier and the $Si_3N_4$ passivation layers deplete the InGaAs channel layer more and thus decreases the electron current passing the channel layer and thus the impact ionization in the channel become smaller. In addition, the replaced InGaAs/InP composite channel with the same thickness in the same asymmetrically recessed structure increases the breakdown voltage to 5 V due to the smaller impact ionization and mobility of the InP layer at high drain voltage.