The absence of large-size gallium nitride(GaN) substrates with low dislocation density remains a primary bottleneck for advancing GaN-based devices. Here, we demonstrate the achievement of 8-inch freestanding GaN subs...The absence of large-size gallium nitride(GaN) substrates with low dislocation density remains a primary bottleneck for advancing GaN-based devices. Here, we demonstrate the achievement of 8-inch freestanding GaN substrates grown by hydride vapor phase epitaxy. Critical to this achievement is the improvement in gas-flow uniformity, which ensures exceptional thickness homogeneity and enables the crack-free growth of GaN. After laser lift-off(LLO) separation, the freestanding GaN substrate exhibits superior crystal quality, evidenced by full width at half maximum values of 68 and 54 arcsec for X-ray diffraction rocking curves of(002) and(102) planes, alongside a low dislocation density of 1.6 × 10^(6) cm^(-2). This approach establishes a robust pathway for the production of large-size GaN substrates, which are essential for advancing next-generation power electronics and high-efficiency photonics.展开更多
β-Ga_(2)O_(3)is a promising candidate for solarblind ultraviolet photodetection owing to its suitable bandgap of approximately 4.9 eV,excellent photoresponse characteristics,and high stability.However,the lack of a s...β-Ga_(2)O_(3)is a promising candidate for solarblind ultraviolet photodetection owing to its suitable bandgap of approximately 4.9 eV,excellent photoresponse characteristics,and high stability.However,the lack of a sufficient driving force within the material leads to extensive bulk charge recombination,limiting its photocurrent and thus posing significant challenges in designing high-performance Ga_(2)O_(3)-based photodetection.In this study,we propose a gradient doping strategy to achieve a Sn-doping concentration gradient along theβ-Ga_(2)O_(3)film thickness.By combining sol-gel synthesis with rapid thermal annealing,a spatially graded band structure with a full-space built-in electric field is constructed,which increases the width of band bending over a large region and is crucial for significantly enhancing carrier separation and transport in the bulk.The resulting gradient Sn-dopedβ-Ga_(2)O_(3)enables exceptional photoelectric performance without an external bias under 254 nm irradiation,including a superior responsivity of 66.88 mA W^(-1),a high detectivity of 8.12×10^(11)Jones,and a fast rise/decay time of 79/65 ms,outstanding most existing similar reported photoelectrochemical(PEC)type optoelectronic devices.Additionally,the device exhibits excellent long-term stability and enables high-resolution underwater ultraviolet imaging.This study demonstrates that the gradient doping strategy provides a feasible approach for enhancing the PEC performance ofβ-Ga_(2)O_(3)photoelectrodes.展开更多
Gallium oxide(Ga_(2)O_(3))is a promising material for next-generation power devices due to its ultrawide bandgap and extremely high critical electric field strength;however,the strong anisotropy and cleavage tendency ...Gallium oxide(Ga_(2)O_(3))is a promising material for next-generation power devices due to its ultrawide bandgap and extremely high critical electric field strength;however,the strong anisotropy and cleavage tendency of Ga_(2)O_(3)pose significant challenges for high-precision surface processing.In this work,a systematic study was conducted through tribological analysis of monocrystalline(001)β-Ga_(2)O_(3).Initially,reciprocal sliding tests were conducted onβ-Ga_(2)O_(3)along different crystallographic directions,[100]and[010].The results revealed that the[100]direction was more wear resistant,while the[010]direction was more prone to failure.Indentation experiments on(001)β-Ga_(2)O_(3)showed extensive slip and cleavage cracking along different crystallographic orientations,indicating that mechanical wear might dominate the wear mode of this material.Subsequently,sliding tests under various environmental conditions revealed that the wear rate was correlated with humidity.Additionally,β-Ga_(2)O_(3)exhibited time-dependent frictional behavior,with its coefficient of friction stabilizing around 0.1,0.5,and 0.9 at different stages during the wear test.These findings indicate that the frictional behavior of Ga_(2)O_(3)is closely linked to the state of its surface.This study provides critical insights into the tribological behavior of Ga_(2)O_(3)and offers guidance for ultraprecision machining of this material.展开更多
基金supported by the National Key Research and Development Program of China (Nos. 2022YFB3605203 and 2022YFB3608100)the National Natural Science Foundation of China (Nos. 62321004, 62227817, and 62374001)。
文摘The absence of large-size gallium nitride(GaN) substrates with low dislocation density remains a primary bottleneck for advancing GaN-based devices. Here, we demonstrate the achievement of 8-inch freestanding GaN substrates grown by hydride vapor phase epitaxy. Critical to this achievement is the improvement in gas-flow uniformity, which ensures exceptional thickness homogeneity and enables the crack-free growth of GaN. After laser lift-off(LLO) separation, the freestanding GaN substrate exhibits superior crystal quality, evidenced by full width at half maximum values of 68 and 54 arcsec for X-ray diffraction rocking curves of(002) and(102) planes, alongside a low dislocation density of 1.6 × 10^(6) cm^(-2). This approach establishes a robust pathway for the production of large-size GaN substrates, which are essential for advancing next-generation power electronics and high-efficiency photonics.
基金supported by the National Natural Science Foundation of China(12304102,62574029)Natural Science Foundation of Chongqing(CSTB2023NSCQ-MSX0479)+1 种基金Science and Technology Research Project of Chongqing Education Committee(KJQN202400558)Doctoral Scientific Research Fund of Chongqing Normal University(23XLB029)。
文摘β-Ga_(2)O_(3)is a promising candidate for solarblind ultraviolet photodetection owing to its suitable bandgap of approximately 4.9 eV,excellent photoresponse characteristics,and high stability.However,the lack of a sufficient driving force within the material leads to extensive bulk charge recombination,limiting its photocurrent and thus posing significant challenges in designing high-performance Ga_(2)O_(3)-based photodetection.In this study,we propose a gradient doping strategy to achieve a Sn-doping concentration gradient along theβ-Ga_(2)O_(3)film thickness.By combining sol-gel synthesis with rapid thermal annealing,a spatially graded band structure with a full-space built-in electric field is constructed,which increases the width of band bending over a large region and is crucial for significantly enhancing carrier separation and transport in the bulk.The resulting gradient Sn-dopedβ-Ga_(2)O_(3)enables exceptional photoelectric performance without an external bias under 254 nm irradiation,including a superior responsivity of 66.88 mA W^(-1),a high detectivity of 8.12×10^(11)Jones,and a fast rise/decay time of 79/65 ms,outstanding most existing similar reported photoelectrochemical(PEC)type optoelectronic devices.Additionally,the device exhibits excellent long-term stability and enables high-resolution underwater ultraviolet imaging.This study demonstrates that the gradient doping strategy provides a feasible approach for enhancing the PEC performance ofβ-Ga_(2)O_(3)photoelectrodes.
基金financial support from the Shenzhen Key Laboratory of Intelligent Robotics Flexible and Manufacturing Systems(Grant No.ZDSYS20220527171403009)the Shenzhen Science and Technology Innovation Commission(Grant No.20231115111658002).
文摘Gallium oxide(Ga_(2)O_(3))is a promising material for next-generation power devices due to its ultrawide bandgap and extremely high critical electric field strength;however,the strong anisotropy and cleavage tendency of Ga_(2)O_(3)pose significant challenges for high-precision surface processing.In this work,a systematic study was conducted through tribological analysis of monocrystalline(001)β-Ga_(2)O_(3).Initially,reciprocal sliding tests were conducted onβ-Ga_(2)O_(3)along different crystallographic directions,[100]and[010].The results revealed that the[100]direction was more wear resistant,while the[010]direction was more prone to failure.Indentation experiments on(001)β-Ga_(2)O_(3)showed extensive slip and cleavage cracking along different crystallographic orientations,indicating that mechanical wear might dominate the wear mode of this material.Subsequently,sliding tests under various environmental conditions revealed that the wear rate was correlated with humidity.Additionally,β-Ga_(2)O_(3)exhibited time-dependent frictional behavior,with its coefficient of friction stabilizing around 0.1,0.5,and 0.9 at different stages during the wear test.These findings indicate that the frictional behavior of Ga_(2)O_(3)is closely linked to the state of its surface.This study provides critical insights into the tribological behavior of Ga_(2)O_(3)and offers guidance for ultraprecision machining of this material.
