P. Chang

Achieving 1nm capacitive effective thickness in atomic layer deposited HfO2 on In0.53Ga0.47As

A capacitive effective thickness (CET) value of 1.0nm has been achieved in atomic layer deposited (ALD) high κ dielectrics HfO2 on In0.53Ga0.47As∕InP. The key is a short air exposure under 10min between removal of the freshly grown semiconductor epilayers and loading to the ALD reactor. This has led to minimal formation of the interfacial layer thickness, as confirmed using x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. The measured electrical characteristics of metal-oxide-semiconductor diodes of Au∕Ti∕HfO2(4.5nm)∕In0.53Ga0.47As showed a low leakage current density of 3.8×10−4A∕cm2 at VFB+1V, which is about eight orders of magnitudes lower than that of SiO2 with the same CET. The capacitance-voltage curves show an overall κ value of 17–18, a nearly zero flatband shift, and an interfacial density of states Dit of 2×1012cm−2eV−1.A capacitive effective thickness (CET) value of 1.0nm has been achieved in atomic layer deposited (ALD) high κ dielectrics HfO2 on In0.53Ga0.47As∕InP. The key is a short air exposure under 10min between removal of the freshly grown semiconductor epilayers and loading to the ALD reactor. This has led to minimal formation of the interfacial layer thickness, as confirmed using x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. The measured electrical characteristics of metal-oxide-semiconductor diodes of Au∕Ti∕HfO2(4.5nm)∕In0.53Ga0.47As showed a low leakage current density of 3.8×10−4A∕cm2 at VFB+1V, which is about eight orders of magnitudes lower than that of SiO2 with the same CET. The capacitance-voltage curves show an overall κ value of 17–18, a nearly zero flatband shift, and an interfacial density of states Dit of 2×1012cm−2eV−1.

A Compact 0.1–14-GHz Ultra-Wideband Low-Noise Amplifier in 0.13-

A compact ultra-wideband low-noise amplifier (LNA) with a 12.4-dB maximum gain, a 2.7-dB minimum noise figure (NF), and a bandwidth over 0.1-14 GHz is realized in a 0.13-μm CMOS technology. The circuit is basically an inductorless configuration using the resistive-feedback and current-reuse techniques for wideband and high-gain characteristics. It was found that a small inductor of only 0.4 nH can greatly improve the circuit performance, which enhances the bandwidth by 23%, and reduces the NF by 0.94 dB (at 10.6 GHz), while only consuming an additional area of 80 × 80 μm2. The LNA only occupies a core area of 0.031 mm , and consumes 14.4 mW from a 1.8-V supply.

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An ultra-low-power 60 GHz low-noise amplifier (LNA) with a 12.5 dB peak gain and a 5.4 dB minimum NF is demonstrated in a 90 nm CMOS technology. The LNA is composed of four cascaded common-source stages with the gate-source transformer feedback applied to the input stage for simultaneous noise and input matching. Also, the drain-source transformer feedback is used in the following stages for gain enhancement and interstage/output matching. This LNA consumes only 4.4 mW from a 1 V supply with a compact core area of 0.047 .

CMOS

Spin pumping transfers the spin momentum of the magnetization precession to the conduction electrons and forms pure spin currents, and was investigated in the ferromagnetic epitaxial Fe3Si films and polycrystalline Py films covered with normal metal (Pt, Au) overlayers, respectively. With the applied microwave applied from a cavity and an in-plane magnetic field, an electric voltage due to inverse spin-Hall effect is detected under the ferromagnetic resonance condition. A linear relationship between the measured voltage and microwave power has been obtained, consistent with a theoretical model. The spin Hall angles of Pt and Au as deduced from the present Py and Fe3Si data are in agreement with the published values. A very large voltage signal is observed for Fe3Si/Au film with in-situ capping of Au, suggesting the possibility of the future applications for the spintronic devices.

An Ultra-Low-Power Transformer-Feedback 60 GHz Low-Noise Amplifier in 90 nm CMOS

The scalability of molecular beam epitaxy grown Ga2O3(Gd2O3)∕In0.2Ga0.8As∕GaAs with in situ Al2O3 capping layers has been studied, in which the InGaAs surface Fermi level has been unpinned. The electrical and structural properties were improved with rapid thermal annealing to high temperatures of 800°C under N2 flow. As Ga2O3(Gd2O3) is scaled down to 8.5nm, the dielectric constant maintained at 14–15, similar to those of thicker oxides, resulting in an equivalent oxide thickness of 2.3nm. A low gate oxide leakage current density of 10−9A∕cm2 at ∣VG−Vfb∣=1, small flatband voltage shift (ΔVfb), low interfacial density of states (Dit) of (1–3)×1011cm−2eV−1 have been achieved.

Detection of inverse spin Hall effect in epitaxial ferromagnetic Fe3Si films with normal metals Au and Pt

Direct measurements of band profile and band offsets across the Gd2O3/GaAs(100) hetero-interface have been performed using cross-sectional scanning tunneling microscopy and spectroscopy. The spatial variation of the local density of states with atomic precision revealed the interfacial band alignment in this model high-κ/III-V system. In conjunction with the theoretical modeling, the band offsets for both conduction and valence states are identified, revealing critical information about the electrostatic potential landscape of the GaAs semiconductor transistor with a Gd2O3 gate dielectric.

Oxide scalability in Al2O3∕Ga2O3(Gd2O3)∕In0.20Ga0.80As∕GaAs heterostructures

In0.2Ga0.8As was effectively passivated using in situ molecular beam epitaxy deposited Al2O3/HfO2 and HfO2–Al2O3(HfAlO)/HfO2. HfO2 3 ML (monolayer) thick was epitaxially grown on InGaAs, as monitored by reflection high-energy electron diffraction. Al2O3 3 nm thick and HfAlO 4 nm thick were used to cap 3 ML epitaxial HfO2 due to their superior thermal stability up to 800 °C. Well-behaved capacitance-voltage characteristics with small capacitance dispersion between 10 and 500 kHz were obtained in both Al2O3/HfO2/InGaAs/GaAs and HfAlO/HfO2/InGaAs/GaAs, with the capacitance effective thickness values of the dielectrics being 1.46 and 1.18 nm, respectively. Particularly, HfAlO/HfO2/InGaAs/GaAs exhibited low leakage current density (2.9×10−4 A/cm2) at |VG-VFB|=1, good thermal stability up to 800 °C, and an equivalent oxide thickness of 1 nm.

Atomic-scale determination of band offsets at the Gd2O3/GaAs (100) hetero-interface using scanning tunneling spectroscopy

Self-aligned inversion-channel In<inf>0.53</inf>Ga<inf>0.47</inf>As n-MOSFETs with ex-situ atomic-layer-deposited Al<inf>2</inf>O<inf>3</inf> and in-situ ultra-high-vacuum deposited Al<inf>2</inf>O<inf>3</inf>/Ga<inf>2</inf>O<inf>3</inf>(Gd<inf>2</inf>O<inf>3</inf>) as gate dielectrics have been demonstrated. Both devices exhibit excellent DC characteristics, including high drain currents and transconductances. In addition, RF characteristics of both devices were analyzed; without using any isolation, non de-embedded current gain cutoff frequency (fT) and maximum oscillation frequency (f<inf>max</inf>) of ∼ 3.1 and 1.1 GHz (ALD-Al<inf>2</inf>O<inf>3</inf>) and of ∼ 17.9 and 11.2 GHz (MBE-Al<inf>2</inf>O<inf>3</inf>/Ga<inf>2</inf>O<inf>3</inf>(Gd<inf>2</inf>O<inf>3</inf>)), respectively, have been obtained.

Passivation of InGaAs using in situ molecular beam epitaxy Al2O3/HfO2 and HfAlO/HfO2

We report magneto-optical Kerr microscopy study of the magnetic reversal behavior of Fe3Si/GaAs(100) epitaxial thin films grown by molecular beam epitaxy. Results are described in the context of superconducting quantum interference device and Kerr effect vector magnetometry to study the magnetic switching behavior. By tuning the Fe concentration of the samples from 75% to 83%, we found that the ratio of uniaxial to cubic anisotropy constants γ (= |Ku/K1|) would tremendously vary from 0.06 to 0.3. When the field was applied along the easy axis of Fe3Si samples, a step feature was observed in the M-H loops. This feature has been resolved in the domain image by Kerr microscopy, in which we observed a two-switching behavior at the field where the step feature occurred. These can be qualitatively understood by considering the ratio γ.

Self-aligned inversion channel In 0.53 Ga 0.47 As N-MOSFETs with ALD-Al 2 O 3 and MBE-Al 2 O 3 /Ga 2 O 3 (Gd 2 O 3 ) as gate dielectrics

An overview is given on advances of science and devices of InGaAs, Ge, and GaN MOS capacitors and inversion-channel and depletion-mode MOSFET’s, with emphasis on the results using ultra-high vacuum (UHV) deposited Ga2O3(Gd2O3) [GGO] and atomic layer deposited (ALD) oxides as high-k dielectrics. Very importantly, no interfacial layers are employed in these MOS devices. Low interfacial densities of states (D it ) as well as low electrical leakage currents have been obtained. Moreover, thermodynamic stability was attained with GGO/InGaAs, as the hetero-structures were rapid thermal annealed to 800–900 °C. The oxide remains amorphous and the interface retains its atomic smoothness and sharpness. The oxide scalability with capacitance equivalent thickness (CET) of £1 nm has been achieved in GGO and ALD-HfO2 on InGaAs. Interfacial chemical properties and band parameters of valence band offsets, conduction band offsets, and oxide band gaps in the high-k’s/InGaAs are determined using x-ray photoelectron spectroscopy and electrical leakage transport. Inversion-channel and/or depletion mode InGaAs, GaN, and Ge MOSFET’s were fabricated; in particular, a self-aligned inversion-channel In0.53Ga0.47As MOSFET, made of Al2O3 (2 nm)/GGO (5 nm) gate oxide and TiN metal gate at 1 mm gate length, has reached a world - record drain current and transconductance.