arXiv subjects

Sriram Krishnamoorthy

Publications and source records attributed to Sriram Krishnamoorthy.

At least 19 recordsLinked to original sources

arXiv2026

4 MV/cm (010) $\beta$-Ga$_2$O$_3$ Heterojunction Diodes Realized by Low-Damage e-Beam NiO$_x$ Interlayers

We report on the utilization of a low-damage e-beam NiO$_x$ deposition process to realize field-plated heterojunction diodes (FP-HJDs) on (010) $\beta$-Ga$_2$O$_3$ films with high critical breakdown field strengths beyond 4 MV/cm and power figure of merits (PFOM) of >1 GW/cm$^2$. Diodes were fabricated on a 2.67 $\times$ 10$^{16}$ cm$^{-3}$ intentionally doped 6.2 $\mu$m thick epitaxial layer grown by metalorganic chemical vapor deposition (MOCVD) on a conductive Sn-doped $\beta$-Ga$_2$O$_3$ (010) substrate using TMGa, O$_2$, Ar carrier gas, and SiH$_4$ as the silicon dopant source. The mesa etched FP-HJD devices utilized a thin 7 nm e-beam NiO$_x$ interlayer before the sputtered NiO$_x$ layers to eliminate the effects of sputter-induced ion damage on the (010) epilayers. Current-Voltage measurements resulted in a forward current density of 700 A/cm$^2$ at 4 V, HJD ideality factor of 1.29, a V$_{bi}$ of 2 V, rectification ratio of 10$^{11}$, and a differential specific on resistance (R$_{on,sp}$) value of 2.36 m$\Omega$ $\times$ cm$^2$. Breakdown of the (010) FP-HJDs was 1.64 kV, leading to a parallel plane electric field at breakdown (E$_{||,max}$) of 4.02 MV/cm and a PFOM of 1.14 GW/cm$^2$, which is a state-of-the-art result for diodes on MOCVD-grown (010) drift layers.

cond-mat.mtrl-sci↗

arXiv2026

VBr >10 kV E-Beam/Sputtered Vertical NiOx/(011) \beta-Ga2O3 HJDs with PFOM >2.3 GW/cm2

Beta-gallium oxide (\beta-Ga2O3) holds enormous potential for medium voltage range power electronic applications. This work reports VBr > 10 kV/Ron,sp = 43 m\Omega*cm2 class edge terminated vertical heterojunction diodes (HJDs) with e-beam/sputtered nickel oxide (NiOx) stack on epitaxial (011) \beta-Ga2O3. The power figure of merit (PFOM) of the HJD exceeds 2.3 GW/cm2. The extracted parallel plane breakdown field is > 5.3 MV/cm, which is the highest reported electric field for thick (011) \beta-Ga2O3 epitaxial drift layer.

physics.app-ph↗

arXiv2026

Evidence of Micron-Scale Ion Damage in (010), (110), and (011) ${\beta}-Ga_2O_3$ Epitaxial Layers

We report on the experimental observation of up to 11.5 ${\mu}m$ deep charge depletion in (010), (110), and (011) ${\beta}-Ga_2O_3$ epitaxial layers due to ion damage from sputtering and inductively coupled plasma (ICP) etching processes whereas charge depletion in (001) ${\beta}-Ga_2O_3$ epitaxial layers was minimal. The orientation-dependent reduction in CV-measured charge density was first observed in $NiO_x$ reactively sputtered heterojunction p-n diodes (HJDs). When compared to reference low-damage Schottky barrier diodes (SBDs), the sputtered HJDs showed a $9.4{\times}$ increase in the specific on resistance $(R_{on,sp})$ and 85% reduction in net donor concentration $(N_D - N_A)$ at zero bias for sputter-damaged HJDs on (010) epitaxial layers whereas HJDs on (001) remained unchanged. Similarly, sputtered SiO2 caused a reduction of $N_D - N_A$ 11.5 ${\mu}m$ deep into the (010) material. Next, SBDs were fabricated on ${\beta}-Ga_2O_3$ surfaces previously etched via a BCl3 based ICP process and compared to SBDs on un-etched surfaces. The (010) SBDs on etched surfaces exhibited a $7.7{\times}$ increase in $R_{on,sp}$ and a 91% reduction in $N_D - N_A$ at zero bias where the (001) etched diodes exhibited little change. Additionally, (110) and (011) diodes fabricated on ICP damaged surfaces also saw a ~82% reduction in $N_D - N_A$ at zero bias, indicating (110) and (011) are also susceptible to ion damage. Damage in the (010), (110), and (011) diodes is potentially caused by energetic ions that travel into the open channels present along the [010] direction and create compensating point defects which could potentially diffuse further.

physics.app-ph↗

arXiv2025

Realization of Insulating Buffer Layers via MOCVD-Grown Nitrogen-Doped (010) \b{eta}-Ga2O3

We present MOCVD-grown, nitrogen-doped \b{eta}-Ga2O3 films as an insulating buffer layer on Fe-doped (010) \b{eta}-Ga2O3 substrates in lieu of 49% HF treatment to remove unintentional silicon at the substrate-epitaxial layer growth interface. N-doped layer thickness and NH3 flow were systematically varied to experimentally determine the lowest nitrogen concentration and thickness of the buffer layer needed to fully compensate the interfacial silicon peak. The NH3 molar flow rate was varied from 200 sccm to 1800 sccm. Results showed fully insulating N-doped layers for samples with NH3 flow rates greater than or equal to 1200 sccm and a thickness of 50 nm. This study demonstrates the efficacy of in-situ, controllably doped nitrogen buffer layers as a mitigation method for unintentional interfacial silicon at the substrate-epitaxial layer growth interface.

cond-mat.mtrl-sci↗

arXiv2025

Electrical Stability of Cr2O3/\b{eta}-Ga2O3 and NiOx/\b{eta}-Ga2O3 Heterojunction Diodes

This work reports the electrical characteristics comparison study between Cr2O3 and NiOx based heterojunction diodes (HJD) on halide vapor phase epitaxy (HVPE) grown \b{eta}-Ga2O3 epitaxial layers. Both as-fabricated Cr2O3 and NiOx HJDs exhibited forward current density in a range of 130-150 A/cm^2 at 5 V with rectifying ratios >10^10 and a reverse leakage current density at 10^-8 A/cm^2 at -5 V. The differential specific on-resistance of Cr2O3 and NiOx HJDs was 12.01 m{\Omega}*cm^2 and 12.05 m{\Omega}*cm^2, respectively. Breakdown voltages of Cr2O3 HJDs ranged from 1.4-1.9 kV and 1.5-2.3 kV for NiOx HJDs. Theoretical band alignment between Cr2O3 and \b{eta}-Ga2O3 was calculated from first principles. The ambient exposed NiOx/HVPE \b{eta}-Ga2O3 HJDs forward current density degraded after 10 days while that of Cr2O3/HVPE \b{eta}-Ga2O3 HJDs remained nearly unchanged after the same amount of time. It was later confirmed that the ambient exposed sputtered NiOx sheet resistance (Rsh) degradation gave rise to the reduction of the forward current density of the NiOx based HJDs, and water (H2O) was qualitatively determined to be the agent attributed to the forward conduction degradation by measuring the Rsh of NiOx-on-sapphire reference wafer after exposing it to different environments. The Cr2O3/HVPE \b{eta}-Ga2O3 HJD also exhibited enhanced thermal stability compared to the NiOx/\b{eta}-Ga2O3 heterostructures at elevated temperatures. Interfacial nickel gallate (Ga2NiO4) phase formation expected from phase diagrams can explain the reduced thermal stability of NiOx/\b{eta}-Ga2O3 HJDs. This study indicates that Cr2O3 is a stable p-type oxide for the realization of robust multi-kV \b{eta}-Ga2O3 HJDs.

physics.app-ph↗

arXiv2025

Cr2O3/\b{eta}-Ga2O3 Heterojunction Diodes with Orientation-Dependent Breakdown Electric Field up to 12.9 MV/cm

We report the fabrication of Cr2O3/\b{eta}-Ga2O3 heterojunction diodes using reactive magnetron sputtering of Cr2O3 on highly doped \b{eta}-Ga2O3 bulk substrates along (100), (010), (001), (110), and (011) orientation dependence of high electric field handling capability in \b{eta}-Ga2O3. Additional relative permittivity values in (110) and (011) orientations of \b{eta}-Ga2O3 were computed by using first-principles calculation methods for accurate apparent charge density (ND-NA) extraction and breakdown electric field analysis from capacitance-voltage measurements. The HJDs fabricated on n+ (110) exhibited breakdown electric fields >10 MV/cm up to 12.9 MV/cm, showing the highest experimentally observed parallel-plane junction electric field among \b{eta}-Ga2O3-based junctions. Breakdown electric fields among (100), (010), (001), and (011) orientations showed distinct distribution in the range of 5.13-5.26 MV/cm, 5.10-7.05 MV/cm, 2.70-3.33 MV/cm, and 3.88-4.38 MV/cm, respectively, validating the orientational dependence of parallel-plane junction electric field at breakdown in low-symmetry monoclinic \b{eta}-Ga2O3. The parallel-plane breakdown electric fields (EBr,||) reported in this work were extracted when the device experienced catastrophic breakdown at 100 mA/cm^2 current density compliance, and should not be confused with critical electric field (Ec) as a function of drift layer doping concentration, which accounts for electric-field dependent impact ionization coefficients in Si, SiC and GaN. This study can guide the choice of crystal orientation for high performance gallium oxide-based devices that require high electric field handling capability.

cond-mat.mtrl-sci↗

arXiv2025

Control of Extraordinary Optical Transmission in Resonant Terahertz Gratings via Lateral Depletion in an AlGaN-GaN Heterostructure

Periodic metallic gratings on substrates can support a range of electromagnetic modes, such as leaky waveguide, guided-resonant, and Fabry-Perot (FP) cavity modes, which can strongly modulate optical transmission under resonant excitation. Here, we investigate how this coupling can be dynamically manipulated through charge-density control in a laterally patterned AlGaN/GaN heterostructure. The structure comprises metallic stripes separated by regions containing a two-dimensional electron gas (2DEG), forming a periodically modulated interface whose electromagnetic response is governed by the charge density between the stripes. In the unbiased state, the conductive 2DEG screens the incident terahertz field and suppresses excitation of guided modes. When the 2DEG is depleted, the change in boundary conditions allows efficient coupling into substrate resonances, producing a strong modulation at particular frequencies where extraordinary optical transmission (EOT) through the structure takes place. The results highlight the sensitive dependence of guided-mode-resonance (GMR) mediated EOT on inter-stripe charge distribution and demonstrate a direct interplay between carrier dynamics and resonant electromagnetic phenomena in the terahertz regime.

cond-mat.mtrl-sci↗

arXiv2025

kV-Class Lateral NiOx/GaN Super-Heterojunction Diode via Ammonia Molecular Beam Epitaxy (NH3-MBE)

This work reports the demonstration of lateral p-NiOx/p-GaN/n-GaN-based super-heterojunction (SHJ) diodes using p-GaN with additional sputtered p-type nickel oxide (NiOx) layers to realize charge-balanced structures. The heterojunction diode capacitance-voltage (C-V) model is applied to extract effective the acceptor concentration from the p-NiOx. Net donor and acceptor concentration in n-GaN and p-GaN are extracted by using metal-oxide-semiconductor (MOS) test structures. The fabricated p-NiOx/p-GaN/n-GaN SHJ diodes with charge-balanced region between anode and cathode exhibit a forward on-state current density of 10-30 mA/mm across an anode-to-cathode distance (LAC) from 16 μm to 80 μm. The SHJ diodes show rectifying behavior with a maximum on/off ratio of 10^9 and a low reverse leakage density. The highest breakdown voltage achieved for the SHJ diodes is ~2.8 kV with reverse leakage density of 10^-4 mA/mm at ~80% of devices catastrophic breakdown voltage. The SHJ diodes across all types of dimensions exhibit significant breakdown voltage improvements (~6X on average) with ultra-low reverse leakage current compared to corresponding reference structures without a charge-balanced extension, clearly demonstrating the superjunction effect for devices fabricated on GaN epitaxial layer with ~10^17 cm^-3 electron density.

physics.app-ph↗

arXiv2025

2.34 kV \b{eta}-Ga2O3 Vertical Trench RESURF Schottky Barrier Diode with sub-micron fin width

In this letter, we present a kilovolt-class \b{eta}-Ga2O3 vertical trench Schottky barrier diode with a field plate incorporating narrow fin width (Wfin) structures of sub-micron dimensions. We used a nanolaminate dielectric comprising a stack of multiple thin TiO2 and Al2O3 layers as RESURF dielectric and for field plate edge termination. Both Wfin of 200 nm and 500 nm demonstrate excellent on-state performance with specific on-resistance (Ron,sp) of 9.8-12 mohmcm2, and 10^10 rectification ratio. A self-aligned photoresist planarization and etch-back process was employed to expose the top of the fins for Schottky contact formation, eliminating critical lithographic alignment challenges in sub-micron scale processing. We achieved a breakdown of 2.34 kV with very low leakage currents before catastrophic breakdown. The measured breakdown voltage is limited by dielectric breakdown at the trench bottom corner as verified by metal-oxide-semiconductor (MOS) test structure. TCAD simulation shows a reduced electric field at the surface of the metal-semiconductor junction due to the RESURF effect, resulting in very low reverse leakage before breakdown. The parallel plane electric field in the \b{eta} -Ga2O3 is extracted to be 3.8 MV/cm from TCAD simulations using accurately extracted drift layer doping profile from high voltage CV measurements. A power figure of merit of 0.867 GW/cm2(0.56 GW/cm2 with current spreading) was calculated. Enhanced RESURF by integration of high-k dielectrics with self-aligned photoresist planarization, offers a promising pathway towards high figure of merit, low leakage high-performance vertical devices.

physics.app-ph↗

arXiv2025

Kilovolt-Class $β-Ga_2O_3$ Field-Plated Schottky Barrier Diodes with MOCVD-Grown Intentionally $10^{15}$ $cm^{-3}$ Doped Drift Layers

We report on the growth optimization of intentionally low-doped ($10^{15}$ $cm^{-3}$) high-quality $β-Ga_2O_3$ drift layers up to 10 $μm$ thick via MOCVD and the fabrication of kilovolt-class field plated Schottky barrier diodes on these thick drift layers. Homoepitaxial growth was performed on (010) $10^{15}$ $cm^{-3}$ substrates using TMGa as the Ga precursor. Growth parameters were systematically optimized to determine the best conditions for high quality thick growths with the given reactor geometry. Chamber pressure was found to improve the growth rate, mobility, and roughness of the samples. Growth rates of up to 7.2 $μm$/hr., thicknesses of up to 10 $μm$, Hall mobilities of up to 176 $cm^2$/Vs, RMS roughness down to 5.45 nm, UID concentrations as low as $2 \times$ $10^{15}$ $cm^{-3}$, and controllable intentional doping down to $3 \times$ $10^{15}$ $cm^{-3}$ were achieved. Field plated Schottky barrier diodes (FP-SBDs) were fabricated on a $6.5 \times$ $10^{15}$ $cm^{-3}$ intentionally doped 10 $μm$ thick film to determine the electrical performance of the MOCVD-grown material. The FP-SBD was found to have current density $>$100 A/$cm^2$ at 3 V forward bias with a specific differential on resistance ($R_{on,sp}$) of 16.22 m$Ω$.$cm^2$ and a turn on voltage of 1 V. The diodes were found to have high quality anode metal/semiconductor interfaces with an ideality factor of 1.04, close to unity. Diodes had a maximum breakdown voltage of 1.50 kV, leading to a punch-through maximum field of 2.04 MV/cm under the anode metal, which is a state-of-the-art result for SBDs on MOCVD-grown (010) drift layers.

physics.app-ph↗

arXiv2025

Orientation-Dependent \b{eta}-Ga2O3 Heterojunction Diode with Atomic Layer Deposition (ALD) Grown NiO

This work reports the demonstration of ALD-deposited NiO/\b{eta}-Ga2O3 heterojunction diodes (HJDs) on low doped drift layer and highly doped (001) & (100) n+ substrates with experimental observation of a parallel-plane junction electric field as high as 7.5 MV/cm, revealing a crystal orientation dependence in \b{eta}-Ga2O3. We use a novel metalorganic precursor bis(1,4-di-tert-butyl-1,3-diazadienyl) (nickel Ni(tBu2DAD)2) with ozone (O3) to deposit NiO. The NiO/\b{eta}-Ga2O3 HJD on 7.7 μm-thick HVPE-grown drift region exhibited an on-state current density of ~20 A/cm2 at 5 V, ~10-8 A/cm2 reverse leakage at low reverse bias(-5 V), and a rectifying ratio(Jon/Joff) of ~109. The HJD broke down at ~2.2 kV reverse bias, corresponding to a ~3.4 MV/cm parallel-plane junction electric field, with a noise floor reverse leakage (10-8~10-6 A/cm2, nA) at 80% of the device catastrophic breakdown voltage. The NiO/\b{eta}-Ga2O3 HJDs on n+ (001) & (100) highly-doped substrates exhibited breakdown voltages at 12.5-16.0 V and 28.5-70.5 V, respectively, with extracted critical electric field (EC) at 2.30-2.76 MV/cm, and 4.33-7.50 MV/cm, revealing a substrate crystal orientation dependence on breakdown electric field for \b{eta}-Ga2O3. The 7.5 MV/cm EC reported here is one of the highest parallel-plane junction electric fields reported in literature.

cond-mat.mtrl-sci↗

arXiv2024

NiOx/\b{eta}-Ga2O3 Heterojunction Diode Achieving Breakdown Voltage >3 kV with Plasma Etch Field-Termination

This work reports the fabrication and characterization of a NiOx/\b{eta}-Ga2O3 heterojunction diode (HJD) that uses a metallic nickel (Ni) target to deposit NiOx layers via reactive RF magnetron sputtering and lift-off processing with >3 kV breakdown voltage, record-low reverse current leakage under high reverse bias, and high junction electric fields (>3.34 MV/cm). The heterojunction diodes are fabricated via bilayer NiOx sputtering followed by self-aligned mesa-etching for field-termination on both large (1-mm2) and small area (100-μm diameter) devices. The HJD exhibits a ~135 A/cm2 forward current density at 5 V with a rectifying ratio of ~1010. The minimum differential specific on-resistance is measured to be 17.26 mΩ cm2. The breakdown voltage on 100-μm diameter pads was measured to be greater than 3 kV with a noise floor-level reverse leakage current density (10-8~10-6 A/cm2) until 3 kV, accomplishing a parallel-plane junction electric field to be at least 3.34 MV/cm at 3 kV with a power figure of merit (PFOM) >0.52 GW/cm2. Temperature-dependent forward current density-voltage (J-V) measurements are performed from room temperature (25 C) to 200 C which showed a temperature coefficient of resistance (α) equaling 1.56, higher than that of \b{eta}-Ga2O3 Schottky barrier diodes (SBDs), indicating potential conductivity degradation within NiOx at elevated temperatures.

physics.app-ph↗

arXiv2024

Dielectric Reliability and Interface Trap Characterization in MOCVD grown In-situ Al$_2$O$_3$ on $β$-Ga$_2$O$_3$

In this article, we investigate the in-situ growth of Al$_2$O$_3$ on $β$-Ga$_2$O$_3$ using metal-organic chemical vapor deposition (MOCVD) at a high temperature of 800°C. The Al$_2$O$_3$ is grown within the same reactor as the $β$-Ga$_2$O$_3$, employing trimethylaluminum (TMAl) and O$_2$ as precursors without breaking the vacuum. We characterize the shallow and deep-level traps through stressed capacitance-voltage (C-V) and photo-assisted C-V methods. The high-temperature deposited dielectric demonstrates an impressive breakdown field of approximately 10 MV/cm. Furthermore, we evaluate the reliability and lifetime of the dielectrics using time-dependent dielectric breakdown (TDDB) measurements. By modifying the dielectric deposition process to include a high-temperature (800°C) thin interfacial layer and a low-temperature (600°C) bulk layer, we report a 10-year lifetime under a stress field of 3.5 MV/cm along a breakdown field of 7.8 MV/cm.

cond-mat.mtrl-sci↗

arXiv2024

Record-High Electron Mobility and Controlled Low 10$^{15}$ cm$^{-3}$ Si-doping in (010) $β$-Ga$_2$O$_3$ Epitaxial Drift Layers

We report on metalorganic chemical vapor deposition (MOCVD) growth of controllably Si-doped 4.5 $μ$m thick $β$-Ga$_2$O$_3$ films with electron concentrations in the 10$^{15}$ cm$^{-3}$ range and record-high room temperature Hall electron mobilities of up to 200 cm$^2$/V.s, reaching the predicted theoretical maximum room temperature mobility value for $β$-Ga$_2$O$_3$. Growth of the homoepitaxial films was performed on Fe-doped (010) $β$-Ga$_2$O$_3$ substrates at a growth rate of 1.9 $μ$m/hr using TEGa as the Gallium precursor. To probe the background electron concentration, an unintentionally doped film was grown with a Hall concentration of 3.43 x 10$^{15}$ cm$^{-3}$ and Hall mobility of 196 cm$^2$/V.s. Growth of intentionally Si-Doped films was accomplished by fixing all growth conditions and varying only the silane flow, with controllable Hall electron concentrations ranging from 4.38 x 10$^{15}$ cm$^{-3}$ to 8.30 x 10$^{15}$ cm$^{-3}$ and exceptional Hall mobilities ranging from 194 - 200 cm$^2$/V.s demonstrated. C-V measurements showed a flat charge profile with the N$_D^+$ - N$_A^-$ values correlating well with the Hall-measured electron concentration in the films. SIMS measurements showed the silicon atomic concentration matched the Hall electron concentration with Carbon and Hydrogen below detection limit in the films. The Hall, C-V, and SIMS data indicate the growth of high-quality 4.5 $μ$m thick $β$-Ga$_2$O$_3$ films and controllable doping into the mid 10$^{15}$ cm$^{-3}$ range. These results demonstrate MOCVD growth of electronics grade record-high mobility, low carrier density, and thick $β$-Ga$_2$O$_3$ drift layers for next generation vertical $β$-Ga$_2$O$_3$ power devices.

physics.app-ph↗

arXiv2024

Effective uniaxial dielectric function tensor and optical phonons in ($\bar{2}01$)-plane oriented $β$-Ga$_2$O$_3$ films with equally-distributed six-fold rotation domains

Monoclinic $β$-Ga$_2$O$_3$ films grown on $c$-plane sapphire have been shown to exhibit six $(\bar{2}01)$-plane oriented domains, which are equally-spaced-by-rotation around the surface normal and equally-sized-by-volume that render the film optical response effectively uniaxial. We derive and discuss an optical model suitable for ellipsometry data analysis of such films. We model mid- and far-infrared ellipsometry data from undoped and electrically insulating films with an effective uniaxial dielectric tensor based on projections of all phonon modes within the rotation domains parallel and perpendicular to the sample normal, i.e., to the reciprocal lattice vector $\mathbf{g}_{\bar{2}01}$. Two effective response functions are described by model, and found sufficient to calculate ellipsometry data that best-match measured ellipsometry data from a representative film. We propose to render either effective dielectric functions, or inverse effective dielectric functions, each separately for electric field directions parallel and perpendicular to $\mathbf{g}_{\bar{2}01}$, by sums of Lorentz oscillators, which permit to determine either sets of transverse optical phonon mode parameters, or sets of longitudinal optical phonon mode parameters, respectively. Transverse optical modes common to both dielectric functions can be traced back to single crystal modes with $B_{\mathrm{u}}$ character, while modes with $A_{\mathrm{u}}$ character only appear within the dielectric function for polarization perpendicular to the sample surface. The thereby obtained parameter sets reveal all phonon modes anticipated from averaging over the six-fold rotation domains of single crystal $β$-Ga$_2$O$_3$, but with slightly shifted transverse optical, and completely different longitudinal optical phonon modes.

cond-mat.mtrl-sci↗

arXiv2024

Utilizing (Al, Ga)2O3/Ga2O3 superlattices to measure cation vacancy diffusion and vacancy-concentration-dependent diffusion of Al, Sn, and Fe in \b{eta} -Ga2O3

Diffusion of native defects such as vacancies and their interactions with impurities are fundamental in semiconductor crystal growth, device processing, and long-term aging of equilibration and transient diffusion of vacancies are rarely investigated. We used aluminum-gallium oxide/gallium oxide superlattices (SLs) to detect and analyze transient diffusion of cation vacancies during annealing in O2 at 1000-1100 C. Using a novel finite difference scheme for the diffusion equation with time- and space-varying diffusion constant, we extract diffusion constants for Al, Fe, and cation vacancies under the given conditions, including the vacancy concentration dependence for Al. indicate that vacancies present in the substrate transiently diffuse through the SLs, interacting with Sn as it also diffuses. In the case of SLs grown on Sn-doped beta-gallium oxide substrates, gradients observed in the extent of Al diffusion indicate that vacancies present in the substrate transiently diffuse through the SLs, interacting with Sn as it also diffuses. In the case of SLs grown on (010) Fe-doped substrates, the Al diffusion is uniform through the SLs, indicating a depth-uniform concentration of vacancies. We find no evidence in either case for the introduction of gallium vacancies from the free surface at rates sufficient to affect Al diffusion down to ppm concentrations, which has important bearing on the validity of typically-made assumptions of vacancy equilibration. Additionally, we show that unintentional impurities in Sn-doped gallium oxide such as Fe, Ni, Mn, Cu, and Li also diffuse towards the surface and accumulate. Many of these likely have fast interstitial diffusion modes capable of destabilizing devices over time, thus highlighting the importance of controlling unintentional impurities in beta-gallium oxide wafers.

cond-mat.mtrl-sci↗

arXiv2023

The Impact of Logical Errors on Quantum Algorithms

In this work, we explore the impact of logical stochastic Pauli and coherent Z-rotation errors on quantum algorithms. We evaluate six canonical quantum algorithms' intrinsic resilience to the logical qubit and gate errors by performing the Monte Carlo simulations guided by the quantum jump formalism. The results suggest that the resilience of the studied quantum algorithms decreases as the number of qubits and the depth of the algorithms' circuits increase for both Pauli and Z-rotation errors. Our results also suggest that the algorithms split into two different groups in terms of algorithmic resilience. The evolution of Hamiltonian, Simon and the quantum phase estimation algorithms are less resilient to logical errors than Grover's search, Deutsch-Jozsa and Bernstein-Vazirani algorithms.

quant-ph↗

arXiv2023

Over 6 $μ$m thick MOCVD-grown Low-Background Carrier Density (10$^{15}$ cm$^{-3}$) High-Mobility (010) $β$-Ga$_2$O$_3$ Drift Layers

This work reports high carrier mobilities and growth rates, simultaneously in low unintentionally-doped UID (10$^{15}$ cm$^{-3}$) MOCVD-grown thick $β$-Ga$_2$O$_3$ epitaxial drift layers, with thicknesses reaching up to 6.3 $μ$m, using triethylgallium (TEGa) as a precursor. Record high room temperature Hall mobilities of 187-190 cm$^2$/Vs were measured for background carrier density values of 2.4 - 3.5$\times$10$^{15}$ cm$^{-3}$ grown at a rate of 2.2 $μ$m/hr. A controlled background carrier density scaling from 3.3$\times$10$^{16}$ cm$^{-3}$ to 2.4$\times$10$^{15}$ cm$^{-3}$ is demonstrated, without the use of intentional dopant gases such as silane, by controlling the growth rate and O$_2$/TEGa ratio. Films show smooth surface morphologies of 0.8-3.8 nm RMS roughness for film thicknesses of 1.24 - 6.3$μ$m. Vertical Ni Schottky barrier diodes (SBDs) fabricated on UID MOCVD material were compared with those fabricated on hydride vapor phase epitaxy (HVPE) material, revealing superior material and device characteristics. MOCVD SBDs on a 6.3 $μ$m thick epitaxial layer show a uniform charge vs. depth profile of $\sim$2.4$\times$10$^{15}$ cm$^{-3}$, an estimated $μ$$_{drift}$ of 132 cm$^2$/Vs, a breakdown voltage (V$_{BR}$) close to 1.2 kV and a surface parallel plane field of 2.05MV/cm without any electric field management - setting record-high parameters for any MOCVD-grown $β$-Ga$_2$O$_3$ vertical diode to date.

physics.app-ph↗