arXiv subjects

A F M Anhar Uddin Bhuiyan

Publications and source records attributed to A F M Anhar Uddin Bhuiyan.

16 recordsLinked to original sources

arXiv2025

Neutron-Assisted Breakdown Enhancement in $β$-Ga$_2$O$_3$ Schottky Diodes

This study demonstrates a substantial enhancement of breakdown voltage in $β$-Ga$_2$O$_3$ Schottky diodes through an approach that combines fast neutron irradiation with controlled post-irradiation electro-thermal annealing. Devices irradiated with 1 MeV neutrons at a high fluence of 1E15 n/cm^2 exhibited substantial degradation, including a drastic reduction in on-current and an increase in on-resistance. Electrothermal testing, conducted through simultaneous current-voltage (J-V) measurements and thermal annealing, resulted in significant recovery. After four cycles of electro-thermal testing, the devices demonstrated significant improvements in performance, with a substantial recovery of on-current and a reduction in on-resistance compared to the post-radiation condition, approaching pre-radiation levels. Most recovery occurred during the first two cycles, with diminishing improvements in later cycles, indicating that most thermally recoverable traps were mitigated early. Capacitance-voltage (C-V) measurements revealed a substantial reduction in carrier concentration, decreasing from 3.2E16 cm^-3 pre-radiation to 5.5E15 cm^-3 after the first electro-thermal testing cycle, indicating an over 82% reduction. Following the third cycle, the carrier concentration partially recovered to 9.9E15 cm^-3, reflecting a carrier removal rate of ~22 cm^-1. The breakdown voltage exhibited a remarkable enhancement, increasing from approximately 300 V to 1.28 kV (a ~325% improvement) after the first electro-thermal testing, attributed to the reduction in carrier concentration by compensating radiation-induced traps. Subsequent testing reduced breakdown voltage slightly to 940 V due to partial recovery of carrier concentration, but it remained significantly higher than pre-radiation levels.

physics.app-ph↗

arXiv2025

Quasi-Vertical $β$-Ga$_2$O$_3$ Schottky Diodes on Sapphire Using All-LPCVD Growth and Plasma-Free Ga-Assisted Etching

This work demonstrates quasi-vertical beta-Ga2O3 Schottky barrier diodes (SBDs) fabricated on c-plane sapphire using an all-LPCVD, plasma-free process integrating epitaxial growth of high-quality beta-Ga2O3 and in-situ Ga-assisted etching. A 6.3 micron-thick (-201)-oriented beta-Ga2O3 layer was grown on c-sapphire with a 6-degree miscut, comprising a 3.15 micron moderately doped (2.1e17 cm^-3) drift layer and a heavily doped (1e19 cm^-3) contact layer on a UID buffer. Mesa isolation used Ga-assisted LPCVD etching, producing a 60° inclined mesa sidewalls with an etch depth of 3.6 micron. SBDs showed excellent forward J-V behavior: 1.22 V turn-on, 1.29 ideality factor, and 0.83 eV barrier height. Minimum differential specific on-resistance was 8.6 mOhm*cm^2 with high current density (252 A/cm^2 at 5 V). C-V profiling revealed uniform doping at 2.1e17 cm^-3. J-V-T from 25 C to 250 C confirmed thermionic emission. Barrier height increased from 0.80 to 1.16 eV, and ideality factor from 1.31 to 1.42. Reverse leakage current remained low, increasing from ~5e-6 A/cm^2 to ~1e-4 A/cm^2; Ion/Ioff decreased from ~1e7 to 5e5. Breakdown voltages with moderately doped (2.1e17 cm^-3) drift layer ranged between 73 and 100 V, with corresponding fields of 1.66 to 1.94 MV/cm. These results highlight the potential of LPCVD-grown and etched beta-Ga2O3 devices for high-performance power electronic applications.

physics.app-ph↗

arXiv2025

LPCVD based Plasma Damage Free in situ etching of $β$-Ga$_2$O$_3$ using Solid Source Gallium

This work demonstrates a novel in situ etching technique for $β$-Ga$_2$O$_3$ using solid-source metallic Ga in a LPCVD system, enabling clean, anisotropic, plasma damage-free etching. Etching behavior was systematically studied on (-201) $β$-Ga$_2$O$_3$ films and patterned (010) $β$-Ga$_2$O$_3$ substrates as a function of temperature, Ar carrier gas flow, and Ga source-to-substrate distance. The process exhibits vapor transport- and surface-reaction-limited behavior, with etch rates reaching a maximum of $\sim$2.25~$μ$m/hr on (010) substrates at 1050~$^\circ$C and 2 cm spacing. Etch rates decrease sharply with increasing source-to-substrate distance due to reduced Ga vapor availability, while elevated temperatures enhance surface reaction kinetics through increased Ga reactivity and suboxide formation, leading to enhanced etch rates. In-plane anisotropy studies using radial trench patterns reveal that the (100) orientation produces the most stable etch front, characterized by smooth, vertical sidewalls and minimal lateral etching, consistent with its lowest surface free energy. In contrast, orientations such as (101), which possess higher surface energy, exhibit pronounced lateral etching and micro-faceting. As the trench orientation progressively deviates from (100), lateral etching increases. Facet evolution is observed between (100) and (-102), where stepped sidewalls composed of alternating (100) and (-102) segments progressively transition into a single inclined facet, which stabilizes along (100) or (-102) depending on the trench orientation. The (100)-aligned fins exhibit minimal bottom curvature, while (201)-aligned structures display increased under-etching and trench rounding.

physics.app-ph↗

arXiv2025

Thermal Annealing and Radiation Effects on Structural and Electrical Properties of NbN/GaN Superconductor/Semiconductor Junction

In the rapidly evolving field of quantum computing, niobium nitride (NbN) superconductors have emerged as integral components due to their unique structural properties, including a high superconducting transition temperature (Tc), exceptional electrical conductivity, and compatibility with advanced device architectures. This study investigates the impact of high-temperature annealing and high-dose gamma irradiation on the structural and superconducting properties of NbN films grown on GaN via reactive DC magnetron sputtering. The as-deposited cubic δ-NbN (111) films exhibited a high-intensity XRD peak, high Tc of 12.82K, and an atomically flat surface. Annealing at 500 and 950 °C for varying durations revealed notable structural and surface changes. High-resolution STEM indicated improved local ordering, while AFM showed reduced surface roughness after annealing. XPS revealed a gradual increase in the Nb/N ratio with higher annealing temperatures and durations. High-resolution XRD and STEM analyses showed lattice constant modifications in δ-NbN films, attributed to residual stress changes following annealing. Additionally, XRD phi-scans revealed sixfold symmetry in NbN films due to rotational domains relative to GaN. While Tc remained stable after annealing at 500 °C, increasing the annealing temperature to 950 °C degraded Tc to ~8K and reduced the residual resistivity ratio from 0.85 in as-deposited films to 0.29 after 30 minutes. The effects of gamma radiation (5 Mrad (Si)) were also studied, demonstrating minimal changes to crystallinity and superconducting performance, indicating excellent radiation resilience. These findings highlight the potential of NbN superconductors for integration into advanced quantum devices and their suitability for applications in radiation-intensive environments such as space, satellites, and nuclear power plants.

cond-mat.supr-con↗

arXiv2025

Electrical and Structural Properties of In-Situ MOCVD Grown Al$_2$O$_3$/$β$-Ga$_2$O$_3$ and Al$_2$O$_3$/$β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ MOSCAPs

This study investigates the electrical and structural properties of MOSCAPs with in-situ MOCVD-grown Al$_2$O$_3$ dielectrics on (010) $β$-Ga$_2$O$_3$ and $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ films. The Al$_2$O$_3$/$β$-Ga$_2$O$_3$ MOSCAPs showed a strong dependence on Al$_2$O$_3$ deposition temperature. At 900$^\circ$C, reduced voltage hysteresis ($\sim$0.3 V) and improved reverse breakdown voltage (74.5 V) were observed, with breakdown fields of 5.01 MV/cm in Al$_2$O$_3$ and 4.11 MV/cm in $β$-Ga$_2$O$_3$. At 650$^\circ$C, higher hysteresis ($\sim$3.44 V) and lower reverse breakdown voltage (38.8 V) were observed, with breakdown fields of 3.69 MV/cm in Al$_2$O$_3$ and 2.87 MV/cm in $β$-Ga$_2$O$_3$. However, forward breakdown fields improved from 5.62 MV/cm (900$^\circ$C) to 7.25 MV/cm (650$^\circ$C). STEM revealed improved crystallinity and sharper interfaces at 900$^\circ$C, enhancing reverse breakdown performance. For Al$_2$O$_3$/$β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ MOSCAPs, increasing Al composition ($x$ = 5.5\% to 9.2\%) reduced carrier concentration and improved reverse breakdown fields from 2.55 to 2.90 MV/cm in $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ and 2.41 to 3.13 MV/cm in Al$_2$O$_3$. Forward breakdown fields in Al$_2$O$_3$ improved from 5.0 to 5.4 MV/cm as Al composition increased. STEM confirmed compositional homogeneity and excellent stoichiometry of Al$_2$O$_3$ and $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ layers. These findings highlight the robust electrical performance, high breakdown fields, and structural quality of Al$_2$O$_3$/$β$-Ga$_2$O$_3$ and Al$_2$O$_3$/$β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ MOSCAPs for high-power applications.

physics.app-ph↗

arXiv2025

MOCVD growth and band offsets of \k{appa}-phase Ga2O3 on sapphire, GaN, AlN and YSZ substrates

Epitaxial growth of \k{appa}-phase Ga2O3 thin films are investigated on c-plane sapphire, GaN- and AlNon-sapphire, and (100) oriented yttria stabilized zirconia (YSZ) substrates via metalorganic chemical vapor deposition (MOCVD). The structural and surface morphological properties are investigated by comprehensive material characterization. Phase pure \k{appa}-Ga2O3 films are successfully grown on GaN-, AlN-on sapphire, and YSZ substrates through a systematical tuning of the growth parameters including the precursor molar flow rates, chamber pressure and growth temperature, whereas the growth on c-sapphire substrates leads to a mixture of \b{eta}- and \k{appa}polymorphs of Ga2O3 under the investigated growth conditions. The influence of the crystalline structure, surface morphology and roughness of \k{appa}-Ga2O3 films grown on different substrates are investigated as a function of precursor flow rate. High resolution scanning transmission electron microscopy (HR-STEM) imaging of \k{appa}-Ga2O3 films reveals abrupt interfaces between the epitaxial film and the sapphire, GaN and YSZ substrates. The growth of single crystal orthorhombic \k{appa}Ga2O3 films is confirmed by analyzing the STEM nano-diffraction pattern. The chemical composition, surface stoichiometry, and the bandgap energies of \k{appa}-Ga2O3 thin films grown on different substrates are studied by high resolution x-ray photoelectron spectroscopy (XPS) measurements. The type-II (staggered) band alignments at three interfaces between \k{appa}-Ga2O3 and c-sapphire, AlN, and YSZ substrates are determined by XPS, with the exception of \k{appa}-Ga2O3/GaN interface, which shows type I (straddling) band alignment.

cond-mat.mtrl-sci↗

arXiv2025

In-situ MOCVD Growth and Band Offsets of Al$_2$O$_3$ Dielectric on $β$-Ga$_2$O$_3$ and $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ thin films

The in-situ metalorganic chemical vapor deposition (MOCVD) growth of Al$_2$O$_3$ dielectrics on $β$-Ga$_2$O$_3$ and $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ films is investigated as a function of crystal orientations and Al compositions of $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ films. The interface and film qualities of Al$_2$O$_3$ dielectrics are evaluated by high resolution X-ray diffraction (HR-XRD) and scanning transmission electron microscopy (HR-STEM) imaging, which indicate the growth of high quality amorphous Al$_2$O$_3$ dielectrics with abrupt interfaces on (010), (100) and (-201) oriented $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ films. The surface stoichiometries of Al$_2$O$_3$ deposited on all orientations of $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ are found to be well maintained with a bandgap energy of 6.91 eV as evaluated by high resolution x-ray photoelectron spectroscopy, which is consistent with the atomic layer deposited (ALD) Al$_2$O$_3$ dielectrics. The evolution of band offsets at both in-situ MOCVD and ex-situ ALD deposited Al$_2$O$_3$/$β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ are determined as a function of Al composition, indicating the influence of the deposition method, orientation, and Al composition of $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ films on resulting band alignments. Type II band alignments are determined at the MOCVD grown Al$_2$O$_3$/$β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ interfaces for (010) and (100) orientations, whereas type I band alignments with relatively lower conduction band offsets are observed along (-201) orientation. Results from this work revealed that the in-situ MOCVD deposited high quality Al$_2$O$_3$ dielectrics with sharp interfaces can be considered as a viable alternative of commonly used ex-situ deposited (ALD) Al$_2$O$_3$ for developing high performance $β$-Ga$_2$O$_3$ and $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ based devices.

cond-mat.mtrl-sci↗

arXiv2025

Radiation Resilience of $β$-Ga$_2$O$_3$ Schottky Barrier Diodes Under High Dose Gamma Radiation

A systematic investigation of the electrical characteristics of \b{eta}-Ga2O3 Schottky barrier diodes (SBDs) has been conducted under high-dose 60Co gamma radiation, with total cumulative doses reaching up to 5 Mrad (Si). Initial exposure of the diodes to 1 Mrad resulted in a significant decrease in on-current and an increase in on-resistance compared to the pre-radiation condition, likely due to the generation of radiation-induced deep-level acceptor traps. However, upon exposure to higher gamma radiation doses of 3 and 5 Mrad, partial recovery of the device performance occurred, attributed to a radiation annealing effect. The capacitance-voltage (C-V) characterization revealed that the net carrier concentration in the $β$-Ga$_2$O$_3$ drift layer reduced from $\sim$3.19 $\times$ 10$^{16}$ cm$^{-3}$ to $\sim$3.05 $\times$ 10$^{16}$ cm$^{-3}$ after 5 Mrad (Si) irradiation. Temperature-dependent I-V characteristics showed that irradiation leads to a reduction in both forward and reverse current across all investigated temperatures ranging from 25 to 250$^\circ$C, accompanied by slight increases in on-resistance, ideality factors, and Schottky barrier heights. The reverse breakdown characteristics of the $β$-Ga$_2$O$_3$ SBDs showed a slight increase of the breakdown voltage after radiation. Overall, $β$-Ga$_2$O$_3$ Schottky diode exhibits high resilience to gamma irradiation, with performance degradation mitigated by radiation-induced self-recovery, highlighting its potential for radiation-hardened electronic applications in extreme environments.

physics.app-ph↗

arXiv2025

LPCVD Grown Si-Doped $β$-Ga$_2$O$_3$ Films with Promising Electron Mobilities

We systematically investigated the growth of Si-doped $β$-Ga$_2$O$_3$ films using LPCVD system, achieving high electron mobilities of 162 cm$^2$/V.s and 149 cm$^2$/V.s at carrier concentrations of $1.51 \times 10^{17}$ cm$^{-3}$ and $1.15 \times 10^{17}$ cm$^{-3}$, respectively, for homoepitaxial (010) $β$-Ga$_2$O$_3$ films grown on $β$-Ga$_2$O$_3$ substrates and heteroepitaxial (-201) $β$-Ga$_2$O$_3$ films grown on off-axis c-sapphire substrates with 6° miscut, representing the highest mobilities reported for LPCVD-grown $β$-Ga$_2$O$_3$ materials. Carrier concentrations were precisely tuned by varying SiCl$_4$ flow rates at a growth temperature of 1000°C, resulting in concentrations ranging from $1.15 \times 10^{17}$ to $1.19 \times 10^{19}$ cm$^{-3}$, as confirmed by both Hall and C-V measurements. The films exhibited high crystalline quality, confirmed by high-resolution XRD and Raman spectroscopy, indicating phase purity and structural integrity. Surface morphologies characterized by FESEM and AFM imaging showed a strong correlation between carrier concentrations and surface smoothness, with lower concentrations resulting in reduced RMS roughness. SIMS analysis revealed uniform Si incorporation, with low carbon, hydrogen, and chlorine impurities below detection limits, indicating high purity of the films. A high low-temperature peak mobility exceeding 843 cm$^2$/V$\cdot$s was achieved for (-201) $β$-Ga$_2$O$_3$ films at 80 K, highlighting the high purity and low compensation of these films. These findings emphasize the potential of LPCVD growth system for producing high-purity $β$-Ga$_2$O$_3$ films with thickness ranging between ~2.3-11.7 $μ$m and faster growth rates (~4.7-17 $μ$m/hr), promising transport properties, controllable doping, and scalability for developing high power vertical devices.

cond-mat.mtrl-sci↗

arXiv2023

Sub-100 nm β-Ga2O3 MOSFET with 55 GHz fMAX and >100 V breakdown

This letter reports a highly scaled 90 nm gate length beta-Ga2O3 T-gate MOSFET with no current collapse and record power gain cut off frequency (fMAX). The epitaxial stack of 60 nm thin channel MOSFET was grown by Molecular Beam Epitaxy (MBE) and highly doped (n++) contact regrowth was carried out by Metal Organic Chemical Vapour Deposition (MOCVD) in the source/drain region. Maximum on current (IDS, MAX) of 160 mA/mm and transconductance (gm) around 36 mS/mm was measured at VDS= 10 V for LSD= 1.5 micrometer channel length. Transconductance is limited by higher channel sheet resistance (Rsheet). We observed no current collapse for both drain and gate lag measurement even at higher VDG,Q quiescent bias points. This is the first report of Ga2O3 FET showing no current collapse without any external passivation. Breakdown voltage around 125 V was reported for LGD= 1.2 micrometer. We extracted 27 GHz current gain cut off frequency (fT) and 55 GHz fMAX for 20 V drain bias. fMAX value mentioned here is the highest for Ga2O3 and the first demonstration of 55 GHz operation. fT. VBR product of 3.375 THz.V has been calculated which is comparable with state-of-art GaN HEMT. This letter suggests that Ga2O3 can be a suitable candidate for X-band application.

cond-mat.mtrl-sci↗

arXiv2023

Electrical Characteristics of in situ Mg-doped beta-Ga2O3 Current-Blocking Layer for Vertical Devices

The lack of p-type doping has impeded the development of vertical gallium oxide (Ga2O3) devices. Current blocking layers (CBL) using implanted deep acceptors has been used to demonstrate vertical devices. This paper presents the first demonstration of in situ Mg-doped beta-Ga2O3 CBLs grown using metalorganic chemical vapor deposition. Device structures were designed with in-situ Mg doped layers with varied targeted Mg doping concentrations, which were calibrated by quantitative secondary ion mass spectroscopy (SIMS). The effectiveness of the CBL is characterized using temperature dependent current-voltage measurements using n-Mg-doped-n structures, providing crucial insight into the underlying mechanisms. To further validate the experimental results, a TCAD simulation is performed and the electrically active effective doping is found to be dependent on the Mg-doping density, offering a new perspective on the optimization of CBL performance. Breakdown measurements show a 3.4 MV/cm field strength. This study represents a significant step forward in the development of Ga2O3-based devices and paves the way for future advancements in this exciting field.

cond-mat.mtrl-sci↗

arXiv2022

Beta-Ga2O3 MOSFETs with near 50 GHz fMAX and 5.4 MV/cm average breakdown field

This letter reports high-performance $\mathrmβ Ga2O3 thin channel MOSFETs with T-gate and degenerately doped source/drain contacts regrown by MOCVD. Gate length scaling (LG= 160-200 nm) leads to a peak drain current (ID,MAX) of 285 mA/mm and peak trans-conductance (gm) of 52 mS/mm at 10 V drain bias with 23.5 Ohm mm on resistance (Ron). A low metal/n+ contact resistance of 0.078 Ohm mm was extracted from TLM measurement. Ron is dominated by interface resistance between channel and regrown layer. A gate-to-drain breakdown voltage of 192 V is measured for LGD = 355 nm resulting in average breakdown field (E_AVG) of 5.4 MV/cm. This E_AVG is the highest reported among all sub-micron gate length lateral FETs. RF measurements on 200 nm Silicon Nitride (Si3N4) passivated device shows a current gain cut off frequency (f_T) of 11 GHz and record power gain cut off frequency (f_MAX) of 48 GHz. The f_T.V_Br product is 2.11 THz.V for 192 V breakdown voltage. The switching figure of merit exceeds that of silicon and is comparable to mature wide-band gap devices.

cond-mat.mtrl-sci↗

arXiv2021

Large-Size Free-Standing Single-crystal b-Ga2O3 Membranes Fabricated by Hydrogen Implantation and Lift-Off

In this paper, we have demonstrated the large-size free-standing single-crystal b-Ga2O3 NMs fabricated by the hydrogen implantation and lift-off process directly from MOCVD grown b-Ga2O3 epifilms on native substrates. The optimum implantation conditions were simulated with a Monte-Carlo simulation to obtain the high hydrogen concentration with a narrow ion distribution at the desired depth. Two as grown b-Ga2O3 samples with different orientation ([100] and [001]) were used and successfully create 1.2 um thick b-Ga2O3 NMs without any physical damages. These b-Ga2O3 NMs were then transfer-printed onto rigid and flexible substrates such as SiC substrate and polyimide substrate. Various material characterizations were performed to investigate the crystal quality, surface morphology, optical property, mechanical property, and bandgap before and after the lift-off and revealed that good material quality is maintained. This result offers several benefits in that the thickness, doping, and size of b-Ga2O3 NMs can be fully controlled. Moreover, more advanced b-Ga2O3-based NM structures such as (AlxGa1-x)2O3/Ga2O3 heterostructure NMs can be directly created from their bulk epitaxy substrates thus this result provides a viable route for the realization of high performance b-Ga2O3 NM-based electronics and optoelectronics that can be built on various substrates and platforms.

cond-mat.mtrl-sci↗

arXiv2020

Direct observation of site-specific dopant substitution in Si doped (AlxGa1-x)2O3 via Atom Probe Tomography

In this work, the interaction of n-type dopants in Si doped (AlxGa1-x)2O3 films with varying Al content over the entire composition range (x = 0-100%) was analyzed using atom probe tomography. An almost uniform dopant distribution with dopant density in the range of 1018 cm-3 was obtained in all (AlxGa1-x)2O3 layers containing different Al contents. We have demonstrated that for the single phase \b{eta}-(AlxGa1-x)2O3 films with Al content of x<0.30, dopants prefer to occupy on Ga sites while Al site is preferred for high Al content (x>0.50) (AlxGa1-x)2O3 layers. It was also observed for Al content, x = 0.30-0.50, no specific cationic site occupancy was observed, Si occupies either Al or Ga sites. This can be attributed to highly inhomogeneous layers within this composition range due to which dopant Si atoms are either in the Al-rich or Al-depleted regions.

physics.app-ph↗

arXiv2020

Electrostatic Engineering using Extreme Permittivity Materials for Ultra-wide Bandgap Semiconductor Transistors

The performance of ultra-wide band gap materials like $β$-Ga$_\mathrm{2}$O$_\mathrm{3}$ is critically dependent on achieving high average electric fields within the active region of the device. In this report, we show that high-k gate dielectrics like BaTiO$_\mathrm{3}$ can provide an efficient field management strategy by improving the uniformity of electric field profile in the gate-drain region of lateral field effect transistors. Using this strategy, we were able to achieve high average breakdown fields of 1.5 MV/cm and 4 MV/cm at gate-drain spacing (L$_\mathrm{gd}$) of 6 um and 0.6 um respectively in $β$-Ga$_\mathrm{2}$O$_\mathrm{3}$, at a high channel sheet charge density of 1.8x10$^\mathrm{13}$cm$^\mathrm{-2}$. The high sheet charge density together with high breakdown field enabled a record power figure of merit (V$^\mathrm{2}$$_\mathrm{br}$/R$_\mathrm{on}$) of 376 MW/cm$^\mathrm{2}$ at a gate-drain spacing of 3 um.

physics.app-ph↗

arXiv2020

Probing charge transport and background doping in MOCVD grown (010) $β$-Ga$_{2}$O$_{3}$

A new record-high room temperature electron Hall mobility ($μ_{RT} = 194\space cm^{2}/V\space s$ at $n\sim 8\times 10^{15}\space cm^{-3}$) for $β$-Ga2O3 is demonstrated in the unintentionally doped thin film grown on (010) semi-insulating substrate via metalorganic chemical vapor deposition (MOCVD). A peak electron mobility of $\sim 9500\space cm^{2}/V\space s$ is achieved at 45 K. Further investigation on the transport properties indicate the existence of sheet charges near the epi-layer/substrate interface. Si is identified as the primary contributor to the background carrier in both the epi-layer and the interface, originated from both surface contamination as well as growth environment. Pre-growth hydrofluoric acid cleaning of the substrate lead to an obvious decrease of Si impurity both at interface and in epi-layer. In addition, the effect of MOCVD growth condition, particularly the chamber pressure, on the Si impurity incorporation is studied. A positive correlation between the background charge concentration and the MOCVD growth pressure is confirmed. It is noteworthy that in a $β$-Ga2O3 film with very low bulk charge concentration, even a reduced sheet charge density can play an important role in the charge transport properties.

physics.app-ph↗