The p-n junction is the foundation building structure for manufacturing various electronic and optoelec-tronic devices.Ultrawide bandgap semiconductors are expected to overcome the limited power capability of Si-based...The p-n junction is the foundation building structure for manufacturing various electronic and optoelec-tronic devices.Ultrawide bandgap semiconductors are expected to overcome the limited power capability of Si-based electronic device,however,it is very difficult to achieve efficient bipolar doping due to the asymmetric doping effect,thereby impeding the development of p-n homojunction and related bipolar devices,especially for the Ga_(2)O_(3)-based materials and devices.Here,we demonstrate a unique one-step integrated growth of p-type N-doped(201)β-Ga_(2)O_(3)/n-type Si-doped(¯201)β-Ga_(2)O_(3)films by phase tran-sition and in-situ pre-doping of dopants,and fabrication of fullβ-Ga_(2)O_(3)linearly-graded p-n homojunc-tion diode from them.The fullβ-Ga_(2)O_(3)p-n homojunction diode possesses a large built-in potential of 4.52 eV,a high operation electric field>2.90 MV/cm in the reverse-bias regime,good longtime-stable rectifying behaviors with a rectification ratio of 104,and a high-speed switching and good surge robust-ness with a weak minority-carrier charge storage.Our work opens the way to the fabrication of Ga_(2)O_(3)-based p-n homojunction,lays the foundation for fullβ-Ga_(2)O_(3)-based bipolar devices,and paves the way for the novel fabrication of p-n homojunction for wide-bandgap oxides.展开更多
AlGaN-based solid state UV emitters have many advantages over conventional UV sources. However, UV-LEDs still suffer from numerous challenges, including low quantum efficiency compared to their blue LED counterparts. ...AlGaN-based solid state UV emitters have many advantages over conventional UV sources. However, UV-LEDs still suffer from numerous challenges, including low quantum efficiency compared to their blue LED counterparts. One of the inherent reasons is a lack of carrier localization effect inside fully miscible AlGaN alloys. In the pursuit of phase separation and carrier localization inside the active region of AlGaN UV-LED, utilization of highly misoriented substrates proves to be useful, yet the carrier distribution and recombination mechanism in such structures has seldom been reported. In this paper, a UV-LED with step-bunched surface morphology was designed and fabricated, and the internal mechanism of high internal quantum efficiency was studied in detail. The correlation between microscale current distribution and surface morphology was provided, directly demonstrating that current prefers to flow through the step edges of the epitaxial layers. Experimental results were further supported by numerical simulation. It was found that efficient radiative recombination centers were formed in the inclined quantum well regions. A schematic three-dimensional energy band structure of the multiple quantum wells(MQWs) across the step was proposed and helps in further understanding the luminescence behavior of LEDs grown on misoriented substrates. Finally, a general principle to achieve carrier localization was proposed, which is valid for most ternary Ⅲ-Ⅴ semiconductors exhibiting phase separation.展开更多
We report on the carrier dynamic and electronic structure investigations on AlGaN-based deep-ultraviolet multiple quantum wells (MQWs)with lateral polarity domains.The localized potential maximum is predicted near the...We report on the carrier dynamic and electronic structure investigations on AlGaN-based deep-ultraviolet multiple quantum wells (MQWs)with lateral polarity domains.The localized potential maximum is predicted near the domain boundaries by first-principle calculation,suggesting carrier localization and efficient radiative recombination.More importantly,lateral band diagrams of the MQWs are proposed based on electron affinities and valance band levels calculated from ultraviolet(UV)photoelectron spectroscopy.The proposed lateral band diagram is further demonstrated by surface potential distribution collected by Kelvin probe microscopy and the density-of-state calculation of energy bands.This work illustrates that lateral polarity structures are playing essential roles in the electronic properties of II nitride photonic devices and may provide novel perspective in the realization of high-efficiency UV emitters.展开更多
SemipolarⅢ-nitrides have attracted increasing attention in applications of optoelectronic devices due to the much reduced polarization field.A high-quality semipolar AlN template is the building block of semipolar Al...SemipolarⅢ-nitrides have attracted increasing attention in applications of optoelectronic devices due to the much reduced polarization field.A high-quality semipolar AlN template is the building block of semipolar AlGaN-based deep-ultraviolet light emitting diodes(DUV LEDs),and thus deserves special attention.In this work,a multi-step in situ interface modification technique is developed for the first time,to our knowledge,to achieve high-quality semipolar AlN templates.The stacking faults were efficiently blocked due to the modification of atomic configurations at the related interfaces.Coherently regrown AlGaN layers were obtained on the in situ treated AlN template,and stacking faults were eliminated in the post-grown AlGaN layers.The strains between AlGaN layers were relaxed through a dislocation glide in the basal plane and misfit dislocations at the heterointerfaces.In contrast,high-temperature ex situ annealing shows great improvement in defect annihilation,yet suffers from severe lattice distortion with strong compressive strain in the AlN template,which is unfavorable to the post-grown AlGaN layers.The strong enhancement of luminous intensity is achieved in in situ treated AlGaN DUV LEDs.The in situ interface modification technique proposed in this work is proven to be an efficient method for the preparation of high-quality semipolar Al N,showing great potential towards the realization of high-efficiency optoelectronic devices.展开更多
基金supported by the National Key R&D Program of China(Grant Nos.2022YFB3605500 and 2022YFB3605503).
文摘The p-n junction is the foundation building structure for manufacturing various electronic and optoelec-tronic devices.Ultrawide bandgap semiconductors are expected to overcome the limited power capability of Si-based electronic device,however,it is very difficult to achieve efficient bipolar doping due to the asymmetric doping effect,thereby impeding the development of p-n homojunction and related bipolar devices,especially for the Ga_(2)O_(3)-based materials and devices.Here,we demonstrate a unique one-step integrated growth of p-type N-doped(201)β-Ga_(2)O_(3)/n-type Si-doped(¯201)β-Ga_(2)O_(3)films by phase tran-sition and in-situ pre-doping of dopants,and fabrication of fullβ-Ga_(2)O_(3)linearly-graded p-n homojunc-tion diode from them.The fullβ-Ga_(2)O_(3)p-n homojunction diode possesses a large built-in potential of 4.52 eV,a high operation electric field>2.90 MV/cm in the reverse-bias regime,good longtime-stable rectifying behaviors with a rectification ratio of 104,and a high-speed switching and good surge robust-ness with a weak minority-carrier charge storage.Our work opens the way to the fabrication of Ga_(2)O_(3)-based p-n homojunction,lays the foundation for fullβ-Ga_(2)O_(3)-based bipolar devices,and paves the way for the novel fabrication of p-n homojunction for wide-bandgap oxides.
基金National Key Research and Development Program of China(2016YFB0400802)National Natural Science Foundation of China(61974149)+2 种基金Key Research and Development Program of Zhejiang Province(2019C01080,2020C01145)Science and Technology Innovation 2025 Major Project of Ningbo(2018B10088,2019B10121)Instrument Developing Project of the Chinese Academy of Sciences(YJKYYQ20190074)。
文摘AlGaN-based solid state UV emitters have many advantages over conventional UV sources. However, UV-LEDs still suffer from numerous challenges, including low quantum efficiency compared to their blue LED counterparts. One of the inherent reasons is a lack of carrier localization effect inside fully miscible AlGaN alloys. In the pursuit of phase separation and carrier localization inside the active region of AlGaN UV-LED, utilization of highly misoriented substrates proves to be useful, yet the carrier distribution and recombination mechanism in such structures has seldom been reported. In this paper, a UV-LED with step-bunched surface morphology was designed and fabricated, and the internal mechanism of high internal quantum efficiency was studied in detail. The correlation between microscale current distribution and surface morphology was provided, directly demonstrating that current prefers to flow through the step edges of the epitaxial layers. Experimental results were further supported by numerical simulation. It was found that efficient radiative recombination centers were formed in the inclined quantum well regions. A schematic three-dimensional energy band structure of the multiple quantum wells(MQWs) across the step was proposed and helps in further understanding the luminescence behavior of LEDs grown on misoriented substrates. Finally, a general principle to achieve carrier localization was proposed, which is valid for most ternary Ⅲ-Ⅴ semiconductors exhibiting phase separation.
基金supported by the National Key Research and Development Program of China(2017YFE0131500)the National Natural Science Foundation of China(62104204 and U21A20493)。
基金National Key Researchand Development Program of China(2016YFB0400802)+2 种基金National Natural Science Foundation of China(61704176,61974149)Key Research and Development Program of Zhejiang Province(2019C01080,2020C01145)Ningbo Innovation 2025 Major Project(2018B10088,2019B10121).
文摘We report on the carrier dynamic and electronic structure investigations on AlGaN-based deep-ultraviolet multiple quantum wells (MQWs)with lateral polarity domains.The localized potential maximum is predicted near the domain boundaries by first-principle calculation,suggesting carrier localization and efficient radiative recombination.More importantly,lateral band diagrams of the MQWs are proposed based on electron affinities and valance band levels calculated from ultraviolet(UV)photoelectron spectroscopy.The proposed lateral band diagram is further demonstrated by surface potential distribution collected by Kelvin probe microscopy and the density-of-state calculation of energy bands.This work illustrates that lateral polarity structures are playing essential roles in the electronic properties of II nitride photonic devices and may provide novel perspective in the realization of high-efficiency UV emitters.
基金National Natural Science Foundation of China(61874091,61974149,62104233)Key Research and Development Program of Zhejiang Province(2020C01145)+1 种基金Natural Science Foundation of Zhejiang Province(LQ21F40004,LR22F40004)Youth Innovation Promotion Association of the Chinese Academy of Sciences(2020298)。
文摘SemipolarⅢ-nitrides have attracted increasing attention in applications of optoelectronic devices due to the much reduced polarization field.A high-quality semipolar AlN template is the building block of semipolar AlGaN-based deep-ultraviolet light emitting diodes(DUV LEDs),and thus deserves special attention.In this work,a multi-step in situ interface modification technique is developed for the first time,to our knowledge,to achieve high-quality semipolar AlN templates.The stacking faults were efficiently blocked due to the modification of atomic configurations at the related interfaces.Coherently regrown AlGaN layers were obtained on the in situ treated AlN template,and stacking faults were eliminated in the post-grown AlGaN layers.The strains between AlGaN layers were relaxed through a dislocation glide in the basal plane and misfit dislocations at the heterointerfaces.In contrast,high-temperature ex situ annealing shows great improvement in defect annihilation,yet suffers from severe lattice distortion with strong compressive strain in the AlN template,which is unfavorable to the post-grown AlGaN layers.The strong enhancement of luminous intensity is achieved in in situ treated AlGaN DUV LEDs.The in situ interface modification technique proposed in this work is proven to be an efficient method for the preparation of high-quality semipolar Al N,showing great potential towards the realization of high-efficiency optoelectronic devices.
