We demonstrate over 3 kV gate-pad-connected field plated (GPFP) <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga 2 O 3 lateral MESFETs with high lateral figures 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 <inline-formula> <tex-math notation="LaTeX">1.4~\Omega </tex-math></inline-formula>.mm can be achieved. The GPFP design adopted here using plasma-enhanced chemical vapor deposited (PECVD) SiN x dielectric and SiN x /SiO 2 wrap-around passivation exhibits up to ~14% improved <inline-formula> <tex-math notation="LaTeX">\text{R}_{{\text {ON}}} </tex-math></inline-formula>, up to ~70% improved breakdown voltage (<inline-formula> <tex-math notation="LaTeX">\text{V}_{{\text {BR}}}= \text {V}_{{\text {DS}}}-\text {V}_{{\text {GS}}} </tex-math></inline-formula>) resulting in up to <inline-formula> <tex-math notation="LaTeX">3\times </tex-math></inline-formula> higher LFOM compared to the non-FP <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga 2 O 3 lateral MESFETs. The <inline-formula> <tex-math notation="LaTeX">\text{V}_{{\text {BR}}} </tex-math></inline-formula> (~2.5 kV) and LFOM (355 MW/cm 2 ) measured simultaneously in our GPFP <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga 2 O 3 lateral MESFET (with <inline-formula> <tex-math notation="LaTeX">\text{L}_{{\text {GD}}} = {10}\mu \text{m} </tex-math></inline-formula>) is the highest value achieved in any depletion-mode <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga 2 O 3 lateral device to date.
In this work, a systematic photoluminescence (PL) study on three series of gallium oxide/aluminum gallium oxide films and bulk single crystals is performed including comparing doping, epitaxial ...substrates, and aluminum concentration. It is observed that blue/green emission intensity strongly correlates with extended structural defects rather than the point defects frequently assumed. Bulk crystals or Si-doped films homoepitaxially grown on (010) β-Ga
O
yield an intense dominant UV emission, while samples with extended structural defects, such as gallium oxide films grown on either (-201) β-Ga
O
or sapphire, as well as thick aluminum gallium oxide films grown on either (010) β-Ga
O
or sapphire, all show a very broad PL spectrum with intense dominant blue/green emission. PL differences between samples and the possible causes of these differences are analyzed. This work expands previous reports that have so far attributed blue and green emissions to point defects and shows that in the case of thin films, extended defects might have a prominent role in emission properties.
In this letter, fin-shape tri-gate <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga2O3 lateral MESFETs are demonstrated with a high power figure of merit (PFOM) of ...0.95 GW/cm2 - a record high for any <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga2O3 transistor to date. A low-temperature un-doped buffer-channel stack design is developed which demonstrates record high Hall and drift electron mobilities in doped <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga2O3 channels allowing for low ON resistances (RON) in <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga2O3 MESFETs. Fin-widths (Wfin) were 1.2-<inline-formula> <tex-math notation="LaTeX">1.5~\mu \text{m} </tex-math></inline-formula> and there were 25 fins (Nfin) per device with a trench depth of <inline-formula> <tex-math notation="LaTeX">\sim ~1~\mu \text{m} </tex-math></inline-formula>. A <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga2O3 MESFET with a source-drain length of 6.4 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> exhibits a high ON current (187 mA/mm), low RON (<inline-formula> <tex-math notation="LaTeX">20.5~\Omega </tex-math></inline-formula>.mm) and a high average breakdown field (4.2 MV/cm). All devices show very low reverse leakage until catastrophic breakdown for breakdown voltages (VBR) scaling from 1.1kV to ~3kV. This work demonstrates the potential of channel engineering in improving <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga2O3 device performance towards lower conduction losses for low-to-medium voltage applications.
We report a vertical (001) <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>-Ga 2 O 3 field-plated (FP) Schottky barrier diode (SBD) with a novel extreme permittivity ...dielectric field oxide. A thin drift layer of <inline-formula> <tex-math notation="LaTeX">1.7~\mu {m} </tex-math></inline-formula> was used to enable a punch-through (PT) field profile and very low differential specific on-resistance (<inline-formula> <tex-math notation="LaTeX">\text{R}_{\text {on-sp}} </tex-math></inline-formula>) of 0.32 <inline-formula> <tex-math notation="LaTeX">\text{m}\Omega </tex-math></inline-formula>-cm 2 . The extreme permittivity field plate oxide facilitated the lateral spread of the electric field profile beyond the field plate edge and enabled a breakdown voltage (<inline-formula> <tex-math notation="LaTeX">{V}_{\textit {br}} </tex-math></inline-formula>) of 687 V. The edge termination efficiency increases from 13.2% for non-field plated structure to 61% for high permittivity field plate structure. The surface breakdown electric field was extracted to be 5.45 MV/cm at the center of the anode region using TCAD simulations. The high permittivity field plated SBD demonstrated a record high Baliga's figure of merit (BFOM) of 1.47 GW/cm 2 showing the potential of Ga 2 O 3 power devices for multi-kilovolt class applications.
We demonstrate a new substrate cleaning and buffer growth scheme in β-Ga2O3 epitaxial thin films using metal–organic vapor phase epitaxy (MOVPE). For the channel structure, a low-temperature (LT, 600 ...°C) un-doped Ga2O3 buffer was grown, followed by a transition layer to a high-temperature (HT, 810 °C) Si-doped Ga2O3 channel layers without growth interruption. The (010) Ga2O3 Fe-doped substrate cleaning uses solvent cleaning, followed by additional hydrofluoric acid (49% in water) treatment for 30 min 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. From secondary ion mass spectroscopy (SIMS) analysis, the Si peak atomic density at the substrate interface is found to be 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 (600 °C) buffer layers, it is seen that the Fe forward decay tail from the substrate is very sharp, with a decay rate of ∼9 nm/dec. X-ray off-axis rocking curve ω-scans show very narrow full width at half maximum (FWHM) values, similar to the as-received substrates. These channels show record high electron mobility in the range of 196–85 cm2/V⋅s in unintentionally doped and Si-doped films in the doping range of 2 × 1016–1 × 1020 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 cm2/V⋅s was measured for sheet charge density of 9.2 × 1012 cm−2. This substrate cleaning, combined with the LT buffer scheme, shows the potential of designing Si-doped β-Ga2O3 channels with exceptional transport properties for high-performance Ga2O3-based electron devices.
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