近年来,石墨烯材料由于优异的光电性能获得了广泛关注,并应用于发光二极管的透明电极以取代昂贵的铟锑氧化物(indium tin oxide,ITO)透明电极,但由于石墨烯与p-GaN功函数不匹配,二者很难形成好的欧姆接触,因而造成器件电流扩展差和电压...近年来,石墨烯材料由于优异的光电性能获得了广泛关注,并应用于发光二极管的透明电极以取代昂贵的铟锑氧化物(indium tin oxide,ITO)透明电极,但由于石墨烯与p-GaN功函数不匹配,二者很难形成好的欧姆接触,因而造成器件电流扩展差和电压高等问题.本文将ITO薄层作为石墨烯透明电极与p-Ga N间的插入层,以改善石墨烯与p-Ga N层的欧姆接触.所制备的石墨烯透明电极的方块电阻为252.6Ω/□,石墨烯/ITO复合透明电极的方块电阻为70.1Ω/□;石墨烯透明电极与p-Ga N层的比接触电阻率为1.92×10^–2Ω·cm^2,ITO插入之后,其比接触电阻率降低为1.01×10^–4Ω·cm^2;基于石墨烯透明电极的发光二极管(light emitting diode,LED),在20 m A注入电流下,正向电压为4.84 V,而石墨烯/ITO复合透明电极LED正向电压降低至2.80 V,且光输出功率得到提高.这归因于石墨烯/ITO复合透明电极与p-Ga N界面处势垒高度的降低,进而改善了欧姆接触;另外,方块电阻的降低,使得电流扩展均匀性也得到了提高.所采用的复合透明电极减少了ITO的用量,得到了良好的欧姆接触,为LED透明电极提供了一种可行方案.展开更多
The lattice-matched XBn structures of InAsSb,grown on GaSb substrates,exhibit high crystal quali⁃ty,and can achieve extremely low dark currents at high operating temperatures(HOT).Its superior performance is attribute...The lattice-matched XBn structures of InAsSb,grown on GaSb substrates,exhibit high crystal quali⁃ty,and can achieve extremely low dark currents at high operating temperatures(HOT).Its superior performance is attributed to the unipolar barrier,which blocks the majority carriers while allowing unhindered hole transport.To further explore the energy band and carrier transport mechanisms of the XBn unipolar barrier structure,this pa⁃per systematically investigates the influence of doping on the dark current,photocurrent,and tunneling character⁃istics of InAsSb photodetectors in the PBn structure.Three high-quality InAsSb samples with unintentionally doped absorption layers(AL)were prepared,with varying p-type doping concentrations in the GaSb contact layer(CL)and the AlAsSb barrier layer(BL).As the p-type doping concentration in the CL increased,the device’s turn-on bias voltage also increased,and p-type doping in the BL led to tunneling occurring at lower bias voltages.For the sample with UID BL,which exhibited an extremely low dark current of 5×10^(-6) A/cm^(2).The photocurrent characteristics were well-fitted using the back-to-back diode model,revealing the presence of two opposing space charge regions on either side of the BL.展开更多
Since 1994, the vertical directional solidification （VDS） technique is employed for the growths of bulk crystals-without the seed, without contact to the ampoule wall, without coating and without external pressure, ...Since 1994, the vertical directional solidification （VDS） technique is employed for the growths of bulk crystals-without the seed, without contact to the ampoule wall, without coating and without external pressure, which leads to the detached growth. Growth velocities ranged from 3 mm/h to 10 mm/h, and rotation rates 10-20 rpm have been used. Ingots, 10-20 mm diameter and 60-65 mm length, have been grown with the conical ampoule geometry and these ingots have shown symmetric detachment. Crystals grown under such conditions showed the relatively low dislocation density and the highest carrier mobility,/tn = 5.9 x 104 cm2＂Vl-sl than the crystal grown ever. For the detached crystals, the dislocation density is 104 cm＂2 in conical region, and reached less than 103 cm-2 in the direction of the growth, when the ingots are not in contact with the ampoule wall. Experiments for indium-antimonide （InSb） growth have shown that the 80% growth environments have detachment, 15% entrapped in conical region and 5% attached.展开更多
Gated transport measurements are the backbone of electrical characterization of nanoscale electronic devices. Scanning gate microscopy （SGM） is one such gating technique that adds crucial spatial information, access...Gated transport measurements are the backbone of electrical characterization of nanoscale electronic devices. Scanning gate microscopy （SGM） is one such gating technique that adds crucial spatial information, accessing the localized properties of semiconductor devices. Nanowires represent a central device concept due to the potential to combine very different materials. However, SGM on semiconductor nanowires has been limited to a resolution in the 50-100 nm range. Here, we present a study by SGM of newly developed III-V semiconductor nanowire InAs/GaSb heterojunction Esaki tunnel diode devices under ultra-high vacuum. Sub-5 nm resolution is demonstrated at room temperature via use of quartz resonator atomic force microscopy sensors, with the capability to resolve InAs nanowire facets, the InAs/GaSb tunnel diode transition and nanoscale defects on the device. We demonstrate that such measurements can rapidly give important insight into the device properties via use of a simplified physical model, without the requirement for extensive calculation of the electrostatics of the system. Interestingly, by precise spatial correlation of the device electrical transport properties and surface structure we show the position and existence of a very abrupt （〈10 nm） electrical transition across the InAs/GaSb junction despite the change in material composition occurring only over 30-50 nm. The direct and simultaneous link between nanostructure composition and electrical properties helps set important limits for the precision in structural control needed to achieve desired device performance.展开更多
基金Supported by the Candidate Talents Training Fund of Yunnan Province(202205AC160054)the National Natural Science Foundation of China(62174156)。
文摘The lattice-matched XBn structures of InAsSb,grown on GaSb substrates,exhibit high crystal quali⁃ty,and can achieve extremely low dark currents at high operating temperatures(HOT).Its superior performance is attributed to the unipolar barrier,which blocks the majority carriers while allowing unhindered hole transport.To further explore the energy band and carrier transport mechanisms of the XBn unipolar barrier structure,this pa⁃per systematically investigates the influence of doping on the dark current,photocurrent,and tunneling character⁃istics of InAsSb photodetectors in the PBn structure.Three high-quality InAsSb samples with unintentionally doped absorption layers(AL)were prepared,with varying p-type doping concentrations in the GaSb contact layer(CL)and the AlAsSb barrier layer(BL).As the p-type doping concentration in the CL increased,the device’s turn-on bias voltage also increased,and p-type doping in the BL led to tunneling occurring at lower bias voltages.For the sample with UID BL,which exhibited an extremely low dark current of 5×10^(-6) A/cm^(2).The photocurrent characteristics were well-fitted using the back-to-back diode model,revealing the presence of two opposing space charge regions on either side of the BL.
文摘Since 1994, the vertical directional solidification （VDS） technique is employed for the growths of bulk crystals-without the seed, without contact to the ampoule wall, without coating and without external pressure, which leads to the detached growth. Growth velocities ranged from 3 mm/h to 10 mm/h, and rotation rates 10-20 rpm have been used. Ingots, 10-20 mm diameter and 60-65 mm length, have been grown with the conical ampoule geometry and these ingots have shown symmetric detachment. Crystals grown under such conditions showed the relatively low dislocation density and the highest carrier mobility,/tn = 5.9 x 104 cm2＂Vl-sl than the crystal grown ever. For the detached crystals, the dislocation density is 104 cm＂2 in conical region, and reached less than 103 cm-2 in the direction of the growth, when the ingots are not in contact with the ampoule wall. Experiments for indium-antimonide （InSb） growth have shown that the 80% growth environments have detachment, 15% entrapped in conical region and 5% attached.
文摘Gated transport measurements are the backbone of electrical characterization of nanoscale electronic devices. Scanning gate microscopy （SGM） is one such gating technique that adds crucial spatial information, accessing the localized properties of semiconductor devices. Nanowires represent a central device concept due to the potential to combine very different materials. However, SGM on semiconductor nanowires has been limited to a resolution in the 50-100 nm range. Here, we present a study by SGM of newly developed III-V semiconductor nanowire InAs/GaSb heterojunction Esaki tunnel diode devices under ultra-high vacuum. Sub-5 nm resolution is demonstrated at room temperature via use of quartz resonator atomic force microscopy sensors, with the capability to resolve InAs nanowire facets, the InAs/GaSb tunnel diode transition and nanoscale defects on the device. We demonstrate that such measurements can rapidly give important insight into the device properties via use of a simplified physical model, without the requirement for extensive calculation of the electrostatics of the system. Interestingly, by precise spatial correlation of the device electrical transport properties and surface structure we show the position and existence of a very abrupt （〈10 nm） electrical transition across the InAs/GaSb junction despite the change in material composition occurring only over 30-50 nm. The direct and simultaneous link between nanostructure composition and electrical properties helps set important limits for the precision in structural control needed to achieve desired device performance.
