Rocio Contreras-Guerrero

Properties of epitaxial BaTiO3 deposited on GaAs

Single crystal BaTiO3 (BTO) has been grown epitaxially on GaAs using molecular beam epitaxy with a 2 unit cell SrTiO3 nucleation layer. The oxide film is lattice-matched to GaAs through an in-plane rotation of 45° relative to the (100) surface leading to c-axis orientation of the BaTiO3. X-ray diffraction confirmed the crystallinity and orientation of the oxide film with a full width half maximum of 0.58° for a 7.5 nm thick layer. Piezoresponse force microscopy was used to characterize the ferroelectric domains in the BaTiO3 layer, and a coercive voltage of 1–2 V and piezoresponse amplitude ∼5 pm/V was measured.

InAs hole inversion and bandgap interface state density of 2 x 10(11) cm(-2) eV(-1) at HfO2/InAs interfaces

High-k/InAs interfaces have been manufactured using InAs surface oxygen termination and low temperature atomic layer deposition of HfO2. Capacitance–voltage (C–V) curves revert to essentially classical shape revealing mobile carrier response in accumulation and depletion, hole inversion is observed, and predicted minority carrier response frequency in the hundred kHz range is experimentally confirmed; reference samples using conventional techniques show a trap dominated capacitance response. C–V curves have been fitted using advanced models including nonparabolicity and Fermi-Dirac distribution. For an equivalent oxide thickness of 1.3 nm, an interface state density Dit = 2.2 × 1011 cm−2 eV−1 has been obtained throughout the InAs bandgap.

Field-Effect Mobility of InAs Surface Channel nMOSFET With Low

Frequency (100 Hz ≤ f ≤ 1 MHz) and temperature (-50 ≤ T 20 °C) characteristics of low interface state density D_it high-κ gate-stacks on n-InAs have been investigated. Capacitance-voltage (C-V) curves exhibit typical accumulation/depletion/inversion behavior with midgap D_it of 2 × 10¹¹ and 4 × 10¹¹ cm^-2 eV^-1 at -50 °C and 20 °C, respectively. Asymmetry of low-frequency C-V curves and C-T dependence for negative voltage showing a sharp transition of ≅-20 dB/decade between low- and high-frequency behavior indicate surface inversion. An inversion carrier activation energy and an InAs hole lifetime of 0.32 eV and 2 ns have been extracted, respectively. Surface channel nMOSFETs with gate length L_g = 1 μm, channel thickness = 10 nm, and equivalent oxide thickness (EOT) 1 ≤ EOT ≤ 1.6 nm have been fabricated. For EOT = 1 nm, a subthreshold swing S = 65 mV/decade, transconductance g_m = 1.6 mS/μm, and ON-current I_ON = 426 μA/μm at an OFF-current I_OFF = 100 nA/μm (supply voltage V_dd = 0.5 V) have been measured. Peak electron field-effect mobilities of 6000-7000 cm²/Vs at sheet electron densities of 2-3 × 10¹² cm^-2 were obtained for EOT as small as 1 nm.

D_{\rm it}

We report the first demonstration of InAs FinFETs with fin width W_fin in the range 25-35 nm, formed by inductively coupled plasma etching. The channel comprises defect-free, lattice-matched InAs with fin height H_fin = 20 nm controlled by the use of an etch stop layer incorporated into the device heterostructure. For a gate length L_g = 1 μm, peak transconductance gm,peak = 1430 μS/μm is measured at V_d = 0.5 V demonstrating that electron transport in InAs fins can match planar devices.

Scaled Gate-Stack

One of the major challenges of high mobility complementary metal-oxide-semiconductor (CMOS) circuits is to meet off-current requirements of <100 pA/μm for low stand-by power (LSTP) operation due to the small bandgap (≤0.5 eV) of the channel material (bandgap limit). In this work, we present experimental proof that the bandgap limit can be overcome at nanometer dimensions leveraging the phenomenon of steady state deep depletion (SSDD). The occurrence of SSDD is investigated using high-k capacitors with 5 and 10 nm InAs channel on a n- or p-type doped lattice matched wide bandgap AlAsSb layer. Absence of charge carriers at the off-state band edge is observed for 5 nm InAs channel layers demonstrating occurrence of SSDD and lifting of the off-state bandgap limit providing a path to meet LSTP requirements for future high mobility CMOS.

InAs FinFETs With

In_0.53Ga_0.47As Esaki tunnel diodes grown by molecular beam epitaxy on an Si substrate via a graded buffer and control In_0.53Ga_0.47As Esaki tunnel diodes grown on an InP substrate are compared in this paper. Statistics are used as a tool to show peak-to-valley ratio for the III-V on Si sample and the control that perform similarly below 8.6 × 10^-10 cm^-2. The existence of a critical device area suggests the potential to utilize III-V on Si for other deeply scaled tunnel devices.

\textrm {H}_{\mathrm {fin}}=20

In this work, the impact of ammonium sulfide ((NH4)2S) surface treatment on the electrical passivation of the Al2O3/p-GaSb interface is studied for varying sulfide concentrations. Prior to atomic layer deposition of Al2O3, GaSb surfaces were treated in 1%, 5%, 10%, and 22% (NH4)2S solutions for 10 min at 295 K. The smallest stretch-out and flatband voltage shifts coupled with the largest capacitance swing, as indicated by capacitance-voltage (CV) measurements, were obtained for the 1% treatment. The resulting interface defect trap density (Dit) distribution showed a minimum value of 4 × 1012 cm−2eV−1 at Ev + 0.27 eV. Transmission electron microscopy and atomic force microscopy examination revealed the formation of interfacial layers and increased roughness at the Al2O3/p-GaSb interface of samples treated with 10% and 22% (NH4)2S. In combination, these effects degrade the interface quality as reflected in the CV characteristics.

nm Fabricated Using a Top–Down Etch Process

The integration of functional oxide thin-films on compound semiconductors can lead to a class of reconfigurable spin-based optoelectronic devices if defect-free, fully reversible active layers are stabilized. However, previous first-principles calculations predicted that SrTiO3 thin films grown on Si exhibit pinned ferroelectric behavior that is not switchable, due to the presence of interfacial vacancies. Meanwhile, piezoresponse force microscopy measurements have demonstrated ferroelectricity in BaTiO3 grown on semiconductor substrates. The presence of interfacial oxygen vacancies in such complex-oxide/semiconductor systems remains unexplored, and their effect on ferroelectricity is controversial. Here, we use a combination of aberration-corrected scanning transmission electron microscopy and first-principles density functional theory modeling to examine the role of interfacial oxygen vacancies on the ferroelectric polarization of a BaTiO3 thin film grown on GaAs. We demonstrate that interfacial oxygen ...

Lifting the off-state bandgap limit in InAs channel metal-oxide-semiconductor heterostructures of nanometer dimensions

Record setting III-V MOSFETs are reported. For the first time performance better than state-of-the-art HEMTs is demonstrated. For a MOSFET with 10 nm unstrained InAs surface channel and L_g = 130 nm operating at 0.5 V, on-current as high as I_on = 601 μA/μm (at fixed I_off = 100 nA/μm) is achieved. This record performance is enabled by g_{m, ext} = 2.72 mS/μm and S = 85 mV/dec, DIBL = 40 mV/V, resulting from breakthroughs in epitaxy and III-V/dielectric interface engineering. Measured mobility is 7100 cm²/V.s at n_s = 6.7×10¹² cm^-2. Device simulations further elucidate the performance potential of III-V N-MOSFETs.

Performance Evaluation of In 0.53 Ga 0.47 As Esaki Tunnel Diodes on Silicon and InP Substrates

Electrical interface quality of various high- k dielectrics on GaSb, including Al₂O₃, HfO₂, LaAlO₃, GdScO₃, and HfO₂/Ga₂O₃ bilayer has been studied and compared with reference low (AlGaSb) and high D_it (native oxide) interfaces using photoluminescence intensity measurements for the first time. Al₂O₃ and HfO₂/Ga₂O₃ bilayer dielectrics are identified with the lowest interface recombination velocity (S=7×10⁴ cm/s) and consequently D_it integrated across essentially the entire bandgap. However, S for even the best identified high- k dielectrics is elevated by 140× over the low D_it AlGaSb reference indicating the need of further improvements for envisioned use in Sb based MOSFETs.