J. P. Mannaerts

Properties of high κ gate dielectrics Gd2O3 and Y2O3 for Si

We present the materials growth and properties of both epitaxial and amorphous films of Gd2O3 (κ=14) and Y2O3 (κ=18) as the alternative gate dielectrics for Si. The rare earth oxide films were prepared by ultrahigh vacuum vapor deposition from an oxide source. The use of vicinal Si (100) substrates is key to the growth of (110) oriented, single domain films in the Mn2O3 structure. Compared to SiO2 gate oxide, the crystalline Gd2O3 and Y2O3 oxide films show a reduction of electrical leakage at 1 V by four orders of magnitude over an equivalent oxide thickness range of 10–20 A. The leakage of amorphous Y2O3 films is about six orders of magnitude better than SiO2 due to a smooth morphology and abrupt interface with Si. The absence of SiO2 segregation at the dielectric/Si interface is established from infrared absorption spectroscopy and scanning transmission electron microscopy. The amorphous Gd2O3 and Y2O3 films withstand the high temperature anneals to 850 °C and remain electrically and chemically intact.

Ga2O3 films for electronic and optoelectronic applications

Properties of Ga2O3 thin films deposited by electron‐beam evaporation from a high‐purity single‐crystal Gd3Ga5O12 source are reported. As‐deposited Ga2O3 films are amorphous, stoichiometric, and homogeneous. Excellent uniformity in thickness and refractive index was obtained over a 2 in. wafer. The films maintain their integrity during annealing up to 800 and 1200 °C on GaAs and Si substrates, respectively. Optical properties including refractive index (n=1.84–1.88 at 980 nm wavelength) and band gap (4.4 eV) are close or identical, respectively, to Ga2O3 bulk properties. Reflectivities as low as 10−5 for Ga2O3/GaAs structures and a small absorption coefficient (≊100 cm−1 at 980 nm) were measured. Dielectric properties include a static dielectric constant between 9.9 and 10.2, which is identical to bulk Ga2O3, and electric breakdown fields up to 3.6 MV/cm. The Ga2O3/GaAs interface demonstrated a significantly higher photoluminescence intensity and thus a lower surface recombination velocity as compared to ...

GaAs metal-oxide-semiconductor field-effect transistor with nanometer-thin dielectric grown by atomic layer deposition

A GaAs metal–oxide–semiconductor field-effect transistor (MOSFET) with thin Al2O3 gate dielectric in nanometer (nm) range grown by atomic layer deposition is demonstrated. The nm-thin oxide layer with significant gate leakage current suppression is one of the key factors in downsizing field-effect transistors. A 1 μm gate-length depletion-mode n-channel GaAs MOSFET with an Al2O3 gate oxide thickness of 8 nm, an equivalent SiO2 thickness of ∼3 nm, shows a broad maximum transconductance of 120 mS/mm and a drain current of more than 400 mA/mm. The device shows a good linearity, low gate leakage current, and negligible hysteresis in drain current in a wide range of bias voltage.

High ε gate dielectrics Gd2O3 and Y2O3 for silicon

We report on growth and characterization of both epitaxial and amorphous films Gd2O3 of (e=14) and Y2O3(e=18) as the gate dielectrics for Si prepared by ultrahigh vacuum vapor deposition. The use of vicinal Si (100) substrates is key to the growth of (110) oriented, single-domain films in the Mn2O3 structure. Typical electrical leakage results are 10−3 A/cm2 at 1 V for single domain epitaxial Gd2O3 and Y2O3 films with an equivalent SiO2 thickness, teq of 15 A, and 10−6 A/cm2 at 1 V for smooth amorphous Y2O3 films (e=18) with a teq of only 10 A. For all the Gd2O3 films, the absence of SiO2 segregation at the interface is established from infrared absorption measurements.

GaAs MOSFET with oxide gate dielectric grown by atomic layer deposition

For the first time, a III-V compound semiconductor MOSFET with the gate dielectric grown by atomic layer deposition (ALD) is demonstrated. The novel application of the ALD process on III-V compound semiconductors affords tremendous functionality and opportunity by enabling the formation of high-quality gate oxides and passivation layers on III-V compound semiconductor devices. A 0.65-/spl mu/m gate-length depletion-mode n-channel GaAs MOSFET with an Al/sub 2/O/sub 3/ gate oxide thickness of 160 /spl Aring/ shows a gate leakage current density less than 10/sup -4/ A/cm/sup 2/ and a maximum transconductance of 130 mS/mm, with negligible drain current drift and hysteresis. A short-circuit current-gain cut-off frequency f/sub T/ of 14.0 GHz and a maximum oscillation frequency f/sub max/ of 25.2 GHz have been achieved from a 0.65-/spl mu/m gate-length device.

QUASISTATIC AND HIGH FREQUENCY CAPACITANCE-VOLTAGE CHARACTERIZATION OF GA2O3-GAAS STRUCTURES FABRICATED BY IN SITU MOLECULAR BEAM EPITAXY

Interface properties of Ga2O3–GaAs structures fabricated using in situ multiple‐chamber molecular beam epitaxy have been investigated. The oxide films were deposited on clean, atomically ordered (100) GaAs surfaces at ≂600 °C by electron‐beam evaporation using a Gd3Ga5O12 single‐crystal source. Metal–insulator–semiconductor structures have been fabricated in order to characterize the Ga2O3–GaAs interface by capacitance–voltage measurements in quasistatic mode and at frequencies between 100 Hz and 1 MHz. The formation of inversion layers in both n and p‐type GaAs has been clearly established. Using the quasistatic/high frequency technique, the interface state density has been derived as a function of band gap energy and a midgap interface state density in the mid 1010 cm−2 eV−1 range has been inferred. Charge trapping in the oxide has been revealed as the dominant trapping mechanism.

Low interface state density oxide‐GaAs structures fabricated by in situ molecular beam epitaxy

Several oxide‐GaAs heterostructures were fabricated using in situ multiple‐chamber molecular beam epitaxy. The oxides include SiO2, MgO, and Ga2O3(Gd2O3), all evaporated by an electron beam method. The SiO2 and Ga2O3(Gd2O3) films are amorphous while the MgO films are crystalline and part of the films are epitaxially grown on GaAs(100). Among these heterostructures, the Ga2O3(Gd2O3)–GaAs shows a photoluminescence intensity comparable to that of Al0.45Ga0.55As–GaAs, and forms accumulation and inversion layers as measured from capacitance voltage measurement in quasistatic and high frequency modes.

Low D/sub it/, thermodynamically stable Ga/sub 2/O/sub 3/-GaAs interfaces: fabrication, characterization, and modeling

Thermodynamically stable, low D/sub it/ amorphous Ga/sub 2/O/sub 3/-(100) GaAs interfaces have been fabricated by extending molecular beam epitaxy (MBE) related techniques. We have investigated both in situ and ex situ Ga/sub 2/O/sub 3/ deposition schemes utilizing molecular beams of gallium oxide. The in situ technique employs Ga/sub 2/O/sub 3/ deposition on freshly grown, atomically ordered (100) GaAs epitaxial films in ultrahigh vacuum (UHV); the ex situ approach is based on thermal desorption of native GaAs oxides in UHV prior to Ga/sub 2/O/sub 3/ deposition. Unique electronic interface properties have been demonstrated for in situ fabricated Ga/sub 2/O/sub 3/-GaAs interfaces including a midgap interface state density D/sub it/ in the low 10/sup 10/ cm/sup -2/ eV/sup -1/ range and an interface recombination velocity S of 4000 cm/s. The existence of strong inversion in both n- and p-type GaAs has been clearly established. We will also discuss the excellent thermodynamic and photochemical interface stability. Ex situ fabricated Ga/sub 2/O/sub 3/-GaAs interfaces are inferior but still of a high quality with S=9000 cm/s and a corresponding D/sub it/ in the upper 10/sup 10/ cm/sup -2/ eV/sup -1/ range. We also developed a new numerical heterostructure model for the evaluation of capacitance-voltage (C-V), conductance-voltage (G-V), and photoluminescence (PL) data. The model involves selfconsistent interface analysis of electrical and optoelectronic measurement data and is tailored to the specifics of GaAs such as band-to-band luminescence and long minority carrier response time /spl tau//sub R/. We will further discuss equivalent circuits in strong inversion considering minority carrier generation using low-intensity light illumination.

Demonstration of enhancement-mode p- and n-channel GaAs MOSFETS with Ga2O3(Gd2O3) As gate oxide

Abstract We report the demonstration of both enhancement-mode p - and n -channel GaAs metal oxide semiconductor field effect transistors (MOSFETs) on GaAs semi-insulating substrates using high quality Ga 2 O 3 (Gd 2 O 3 ) as the gate dielectric and the conventional ion-implant technology. The source and drain regions were selectively implanted with Zn or Si for low resistance ohmic contacts for p - or n -MOSFETs, respectively. AuBe/Pt/Au, Ge/Mo/Au-Ge/Mo/Au, and Ti/Pt/Au were deposited for p - and n -ohmic contacts and gate electrode, respectively. The devices, with a 4 × 50 μ m 2 gate geometry, exhibit an extrinsic transconductance of 0.18 and 0.1 mS/mm for p - and n -MOSFETs, respectively, and an excellent gate breakdown field greater than 3 MV cm −1 .

Ga 2 O 3 (Gd 2 O 3 )/InGaAs enhancement-mode n-channel MOSFETs

We have demonstrated the first Ga/sub 2/O/sub 3/(Gd/sub 2/O/sub 3/) insulated gate n-channel enhancement-mode In/sub 0.53/Ga/sub 0.47/As MOSFETs on InP semi-insulating substrate. Ga/sub 2/O/sub 3/(Gd/sub 2/O/sub 3/) was electron beam deposited from a high purity single crystal Ga/sub 5/Gd/sub 3/O/sub 12/ source. The source and drain regions of the device were selectively implanted with Si to produce low resistance ohmic contacts. A 0.75-/spl mu/m gate length device exhibits an extrinsic transconductance of 190 mS/mm, which is an order of magnitude improvement over previously reported enhancement-mode InGaAs MISFETs. The current gain cutoff frequency, f/sub t/, and the maximum frequency of oscillation, f/sub max/, of 7 and 10 GHz were obtained, respectively, for a 0.75/spl times/100 /spl mu/m/sup 2/ gate dimension device at a gate voltage of 3 V and drain voltage of 2 V.