arXiv subjects

Carl Peterson

Publications and source records attributed to Carl Peterson.

18 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

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 $\beta-Ga_2O_3$ 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 $\beta-Ga_2O_3$ drift layers up to 10 $\mu m$ 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 $\mu m$/hr., thicknesses of up to 10 $\mu m$, 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 $\mu m$ 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$\Omega$.$cm^2$ 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↗

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↗

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↗

arXiv2023

Enhancing the Electron Mobility in Si-doped (010) $β$-Ga$_2$O$_3$ films with Low-Temperature Buffer Layers

We demonstrate a new substrate cleaning and buffer growth scheme in $β$-Ga$_2$O$_3$ epitaxial thin films using metalorganic vapor phase epitaxy (MOVPE). For the channel structure, a low-temperature (LT, 600 $^\circ$C) undoped Ga$_2$O$_3$ buffer is grown followed by transition layers to a high-temperature (HT, 810 $^\circ$C) Si-doped Ga$_2$O$_3$ channel layers without growth interruption. The (010) Ga$_2$O$_3$ Fe-doped substrate cleaning uses solvent cleaning followed by an additional HF (49% in water) treatment for 30 mins before the epilayer growth. This step is shown to compensate the parasitic Si channel at the epilayer-substrate interface that originates from the substrate polishing process or contamination from the ambient. SIMS analysis shows the Si peak atomic density at the substrate interface is several times lower than the Fe atomic density in the substrate - indicating full compensation. The elimination of the parasitic electron channel at the epi-substrate interface was also verified by electrical (capacitance-voltage profiling) measurements. In the LT-grown buffer layers, it is seen that the Fe forward decay tail from the substrate is very sharp with a decay rate of $\sim$ 9 nm$/$dec. These channels show record high electron mobility in the range of 196 - 85 cm$^2$/Vs in unintentionally doped and Si-doped films in the doping range of 2$\times$10$^{16}$ to 1$\times$10$^{20}$ cm$^{-3}$. Si delta-doped channels were also grown utilizing this substrate cleaning and the hybrid LT-buffers. Record high electron Hall mobility of 110 cm$^2$/Vs was measured for sheet charge density of 9.2$\times$10$^{12}$ cm$^{-2}$. This substrate cleaning combined with the LT-buffer scheme shows the potential of designing Si-doped $β$-Ga$_2$O$_3$ channels with exceptional transport properties for high performance gallium oxide-based electron devices.

cond-mat.mtrl-sci↗

arXiv2022

Low Resistance Ohmic Contact On Epitaxial MOVPE-grown $β$-Ga$_2$O$_3$ and $β$-(Al$_x$Ga$_1-x$)$_2$ O$_3$ Films

We report on the realization of record low resistance Ohmic contacts to MOVPE-grown heavily Si-doped $β$-Ga$_2$O$_3$ and $β$-(Al$_x$Ga$_1-x$)$_2$ O$_3$ epitaxial films. Transfer length measurement (TLM) patterns were fabricated on the heavily Si-doped homoepitaxial $β$-Ga$_2$O$_3$ films with electron concentration (n) ranging from 1.77 to 3.23e20 cm^-3. Record low specific contact resistance and total contact resistance (Rc) of 1.62e-7 Ohm.cm^2 and 0.023 Ohm.mm were realized for $β$-Ga$_2$O$_3$: Si films with n > 3e20 cm^-3. TLM structures were also fabricated on heavily Si doped coherently strained $β$-(Al$_x$Ga$_1-x$)$_2$ O$_3$ (x=12%, 17% and 22%) films. The film with 12% Al composition (n=1.23e20 cm^-3) showed \r{ho}c of 5.85e-6 Ohm.cm^2, but it increased to 2.19e-4 Ohm.cm^2 for a layer with a 22% Al composition. Annealing the samples post metal deposition has generally led to a decrease in contact resistance, but for high Al content $β$-(Al$_x$Ga$_1-x$)$_2$ O$_3$, the contact resistance did not change significantly after the annealing process. The low contact resistance values measured in this work are very promising for the fabrication of high frequency power devices.

cond-mat.mtrl-sci↗

arXiv2022

High-Mobility Tri-Gate $β$-Ga$_2$O$_3$ MESFETs with a Power Figure of Merit over 0.9 GW/cm$^2$

In this letter, fin-shape tri-gate $β$-Ga$_{2}$O$_{3}$ lateral MESFETs are demonstrated with a high power figure of merit of 0.95 GW/cm$^{2}$ - a record high for any $β$-Ga$_{2}$O$_{3}$ transistor to date. A low-temperature undoped buffer-channel stack design is developed which demonstrates record high Hall and drift electron mobilities in doped $β$-Ga$_{2}$O$_{3}$ channels allowing for low ON resistances R$_{ON}$ in $β$-Ga$_{2}$O$_{3}$ MESFETs. Fin-widths (W$_{fin}$) were 1.2-1.5 $μ$m and there were 25 fins (N$_{fin}$) per device with a trench depth of $\sim$1$μ$m. A $β$-Ga$_2$O$_3$ MESFET with a source-drain length of 6.4 $μ$m exhibits a high ON current (187 mA/mm), low R$_{ON}$ (20.5 $Ω$.mm) and a high average breakdown field (4.2 MV/cm). All devices show very low reverse leakage until catastrophic breakdown for breakdown voltages scaled from 1.1kV to $\sim$3kV. This work demonstrates the potential of channel engineering in improving $β$-Ga$_{2}$O$_{3}$ device performance toward lower conduction losses for low-to-medium voltage applications.

physics.app-ph↗

arXiv2022

Alloyed B-(AlxGa1-x)2O3 bulk Czochralski single B-(Al0.1Ga0.9)2O3 and polycrystals B-(Al0.33Ga0.66)2O3, B-(Al0.5Ga0.5)2O3), and property trends

In this work, bulk Czochralski-grown single crystals of 10 mol. % Al2O3 alloyed B-Ga2O3 - monoclinic 10% AGO or B-(Al0.1Ga0.9)2O3 - are obtained, which show +0.20 eV increase in the bandgap compared with unintentionally doped B-Ga2O3. Further, growths of 33% AGO - B-(Al0.33Ga0.67)2O3 - and 50% AGO - B-(Al0.5Ga0.5)2O3 or B-AlGaO3 - produce polycrystalline single-phase monoclinic material (B-AGO). All three compositions are investigated by x-ray diffraction, Raman spectroscopy, optical absorption, and 27Al nuclear magnetic resonance (NMR). By investigating single phase B-AGO over a large range of Al2O3 concentrations (10 - 50 mol. %), broad trends in the lattice parameter, vibrational modes, optical bandgap, and crystallographic site preference are determined. All lattice parameters show a linear trend with Al incorporation. According to NMR, aluminum incorporates on both crystallographic sites of B-Ga2O3, with a slight preference for the octahedral (GaII) site, which becomes more disordered with increasing Al. Single crystals of 10% AGO were also characterized by x-ray rocking curve, transmission electron microscopy, purity (glow discharge mass spectroscopy and x-ray fluorescence), optical transmission (200 nm - 20 um wavelengths), and resistivity. These measurements suggest that electrical compensation by impurity acceptor doping is not the likely explanation for high resistivity, but rather the shift of a hydrogen level from a shallow donor to a deep acceptor due to Al alloying. .. Cont. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Journal of Applied Physics 131 155702.

cond-mat.mtrl-sci↗

arXiv2022

4.4 kV $β$-Ga$_2$O$_3$ Power MESFETs with Lateral Figure of Merit exceeding 100 MW/cm$^2$

Field-plated (FP) depletion-mode MOVPE-grown $β$-Ga$_2$O$_3$ lateral MESFETs are realized with superior reverse breakdown voltages and ON currents. A sandwiched SiN$_x$ dielectric field plate design was utilized that prevents etching-related damage in the active region and a deep mesa-etching was used to reduce reverse leakage. The device with L$_{GD}$ = 34.5 $μ$m exhibits an ON current (I$_{DMAX}$) of 56 mA/mm, a high I$_{ON}$/I$_{OFF}$ ratio $>$ 10$^8$ and a very low reverse leakage until catastrophic breakdown at $\sim$ 4.4kV. The highest measurable V$_{BR}$ recorded was 4.57 kV (L$_{GD}$ = 44.5 $μ$m). An LFOM of 132 MW/cm$^2$ was calculated for a V$_{BR}$ of $\sim$ 4.4 kV. The reported results are the first $>$ 4kV-class Ga$_2$O$_3$ transistors to surpass the theoretical FOM of Silicon. These are also the highest I$_{DMAX}$ and lowest R$_{ON}$ values achieved simultaneously for any $β$-Ga$_2$O$_3$ device with V$_{BR}$ $>$ 4kV to date. This work highlights that high breakdown voltages (V$_{BR}$), high lateral figure of merit (LFOM) and high ON currents can be achieved simultaneously in $β$-Ga$_2$O$_3$ lateral transistors.

physics.app-ph↗

arXiv2021

Multi-kV class $β$-Ga$_2$O$_3$ MESFETs with a Lateral Figure of Merit up to 355 MW/cm$^2$

We demonstrate over 3 kV gate-pad-connected field plated (GPFP) $β$-Ga$_2$O$_3$ lateral MESFETs with high lateral figure of merit (LFOM) using metalorganic vapor phase epitaxy (MOVPE) grown channel layers and regrown ohmic contact layers. Using an improved low-temperature MOVPE selective area epitaxy process, we show that a total contact resistance to the channel as low as 1.4 $Ω$.mm can be achieved.The GPFP design adopted here using PECVD (plasma-enhanced chemical vapor deposition) deposited SiN$_x$ dielectric and SiN$_x$/SiO$_2$ wrap-around passivation exhibits up to ~14% improved R$_{ON}$, up to ~70% improved breakdown voltage (V$_{BR}$ = V$_{DS}$ - V$_{GS}$) resulting in up to $\sim$3$\times$ higher LFOM compared to non-FP $β$-Ga$_2$O$_3$ lateral MESFETs. The V$_{BR}$ (~2.5 kV) and LFOM (355 MW/cm$^2$) measured simultaneously in our GPFP $β$-Ga$_2$O$_3$ lateral MESFET (with L$_{GD}$ = 10 $μ$m) is the highest value achieved in any depletion-mode $β$-Ga$_2$O$_3$ lateral device.

physics.app-ph↗