Xiuju Zhou

High-Performance Inverted

We report inverted-type In_0.51Al_0.49As/In_0.53Ga_0.47As MOSHEMTs heteroepitaxially grown on GaAs substrates by metal-organic chemical vapor deposition. High 2-D electron gas Hall mobility values of 8200 cm²/V · s at 300 K and 33 900 cm²/V · s at 77 K have been achieved. The buried quantum-well channel design is combined with selectively regrown source/drain (S/D) using a gate-last process. A 120-nm-channel-length MOSHEMT exhibited a maximum drain current of 1884 mA/mm, peak transconductance of 1126 mS/mm at <i>V</i>_ds = 0.5 V, and a subthreshold slope of 135 mV/dec at <i>V</i>_ds = 0.05 V. With the regrown S/D, an ultralow on-state resistance of 156 Ω·μm was obtained.

\hbox{In}_{0.53} \hbox{Ga}_{0.47}\hbox{As}

We report a comparison of material and device characteristics of metamorphic In0.53Ga0.47As channel metal-oxide-semiconductor high-electron mobility transistors (MOSHEMTs) grown on GaAs and Si substrates by metal-organic chemical vapor deposition. A gate-last process was developed to simplify the fabrication of nanoscale channel length devices. Selective source/drain regrowth was incorporated to reduce parasitic resistances. Post-metallization annealing (PMA) was utilized to mitigate the weakened gate electrostatic control in the buried channel. The effect of PMA on the Ti/Al2O3 gate-stack was investigated in detail. Record-low ON-state resistance of 132 and 129 Ω·μm has been achieved in enhancement-mode InGaAs MOSHEMT on GaAs and on Si substrate, respectively. A 120-nm channel length device on GaAs exhibited a figure of merit Q(gm/SS) of 12, whereas a 60-nm channel length In0.53Ga0.47As MOSHEMT on Si demonstrated Q up to 14.

MOSHEMTs on a GaAs Substrate With Regrown Source/Drain by MOCVD

We report inverted-type In_0.51Al_0.49As/In_0.53Ga_0.47As MOSHEMTs grown by MOCVD on a Si substrate. n⁺⁺ InGaAs with an electron density of 4.5 × 10¹⁹ cm^-3 was selectively regrown in the source/drain regions to reduce parasitic resistance while eliminating the conventional gate recess etching. A 30-nm-channel-length device was successfully demonstrated with a maximum drain current of 1698 mA/mm, a peak transconductance of 1074 mS/mm at V_ds = 0.5 V, a subthreshold slope of 172 mV/dec at V_ds = 0.05 V, and a record-low on-resistance of 133 Ω·μm. An effective mobility of 4805 cm²/V· s was also extracted, indicating the high-quality metamorphic growth by MOCVD. In addition, the scalability of the inverted MOSHEMT on a Si substrate from 1 μm down to 30 nm was investigated.

Material and Device Characteristics of Metamorphic

Inverted-type In0.51Al0.49As/In0.53Ga0.47As metal–oxide–semiconductor high-electron-mobility transistor grown by metal organic chemical vapor deposition on a Si substrate was demonstrated. 8 nm atomic-layer-deposited Al2O3 was used as gate dielectric. N++ InGaAs with an electron density of 4.5×1019 cm-3 was selectively regrown in the source/drain regions to reduce parasitic resistance while eliminating the conventional gate recess etching. 130-nm channel-length devices have exhibited a drain current up to 2.03 A/mm at Vds=0.6 V and an ultralow on-resistance of 163 Ω µm. An effective mobility of 2975 cm2 V-1 s-1 was also extracted, indicating the high-quality epitaxial growth by metal organic chemical vapor deposition.

{\rm In}_{0.53}{\rm Ga}_{0.47}{\rm As}

This paper describes the development of 30nm enhancement-mode In_0.53Ga_0.47As MOSFETs grown on Si substrates featuring Al₂O₃/InAlAs composite gate stack with extrinsic transconductance of 1700mS/mm at V_ds=0.5V and on-resistance of 157 Ω·μm. A low-temperature process of post metallization annealing has been developed to achieve enhancement-mode operation. Capacitance-Voltage measurements and TEM observation were carried out to investigate the mechanisms of threshold voltage shift. Furthermore, device scalability down to 30nm is reported.

MOSHEMTs Grown on GaAs and Si Substrates by MOCVD

As scaling technologies are being stretched harder and harder in the roadmap of Si based CMOS, III–V compounds have become competitive alternative channel materials for the next generation high speed and low power transistors. Among various device structures, InGaAs HEMT has been intensively researched in the past few years because of its excellent carrier transport properties [1–3]. However, conventional HEMT structures requiring recessed gate technology may be difficult for digital VLSI applications due to their large footprint and higher parasitic capacitances [4]. Moreover, the gate recess process raises serious concerns in threshold voltage uniformity caused by variations in recess etching depth [5]. Selective Source/Drain (S/D) regrowth, which has been implemented in advanced Si pMOSFET, is an easier and scalable approach to facilitate ohmic contact in HEMT structures, with the benefits of eliminating reliability issues related to gate recess and parasitic reduction. In this paper, we describe the process and preliminary device results of metamorphic HEMTs (mHEMTs) and MOS-HEMTs on GaAs substrates with highly doped In0.53Ga0.47As S/D by selective regrowth using MOCVD.

30-nm Inverted

High-performance implant-free In<inf>0.53</inf>Ga<inf>0.47</inf>As-channel MOSFETs grown on GaAs substrates by Metalorganic Chemical Vapor Deposition (MOCVD) are demonstrated. Atomic-layer-deposited (ALD) Al<inf>2</inf>O<inf>3</inf> was used as gate dielectric on top of a δ-doped In<inf>0.53</inf>Ga<inf>0.47</inf>As/In<inf>0.51</inf>Al<inf>0.49</inf>As metamorphic heterojunction structures grown on GaAs substrates. A 1-µm gate-length MOSFET with 15nm Al<inf>2</inf>O<inf>3</inf> shows a maximum drain current of 590 mA/mm and peak Gm of 501 mS/mm. To the best of our knowledge, these are the highest reported values to date for III–V MOSFETs on GaAs substrates. The maximum gate leakage is 7.2nA/mm at the forward gate bias of 4V and the on resistance is 1491 Ω·µm