In_(0.5)Ga_(0.5)P/GaAs二维空穴气p沟异质结场效应管

提出了一种新颖的 Ga As基 p沟异质结场效应管 (p HFET)概念 ,器件采用了 In0 .5Ga0 .5P/ Ga As异质系统及二维空穴气 (2 DHG)原理以改善 Ga As的空穴输运特性。据此原理研制的器件可在室温下工作 ,其实验结果为 :室温下 ,饱和电流 Idss=6 1m A/ mm,跨导 gm=4 1m S/ mm;77K下 ,饱和电流 Idss=94 m A/ mm,跨导 gm=6 1m S/ mm。预计该器件在微波和数字电路中极佳的电流密度及高频增益 ,因而具有良好的应用潜力。     

156GHz 0.15μm GaAs Metamorphic HEMT器件研制

应用电子束直写技术成功制作了栅长0.15μm的高性能In0.52Al0.48As/In0.53Ga0.47As GaAs MHEMT。从工艺角度,结合器件的小信号等效电路的理论分析,优化了器件源漏间距,从而减小了器件寄生参数,达到了较好的器件性能。最终制作的In0.52Al0.48As/In0.53Ga0.47As MHEMT饱和电流达到495mA/mm,夹断电压-0.8V,在Vgs为-0.19V时的最大非本征跨导gm为1032mS/mm,截止频率ft达到156GHz,最大振荡频率fmax大于150GHz。     

RTD与PHEMT集成的几个关键工艺

在新型的共振隧穿二极管(RTD)器件与PHEMT器件单片集成材料结构上,研究和分析了分立器件的制作工艺,给出了分立器件的制作工艺参数.利用上述工艺成功制作了RTD和PHEMT器件,并在室温下分别测试了RTD器件和PHEMT器件的电学特性.测试表明:在室温下,RTD器件的峰电流密度与谷电流密度之比提高到1.78;PHEMT器件的最大跨导约为120mS/mm,在Vgs＝0.5V时的饱和电流约为270mA/mm.这将为RTD集成电路的研制奠定工艺基础.     

RTD与PHEMT集成的几个关键工艺

在新型的共振隧穿二极管(RTD)器件与PHEMT器件单片集成材料结构上，研究和分析了分立器件的制作工艺，给出了分立器件的制作工艺参数．利用上述工艺成功制作了RTD和PHEMT器件，并在室温下分别测试了RTD器件和PHEMT器件的电学特性．测试表明：在室温下，RTD器件的峰电流密度与谷电流密度之比提高到1.78;PHEMT器件的最大跨导约为120mS/mm,在Vgs＝0.5V时的饱和电流约为270mA/mm．这将为RTD集成电路的研制奠定工艺基础．     

100nm GaAs MHEMT器件研制

应用电子束直写技术成功制作了栅长100nm的高性能In0.52Al0.48As/In0.53Ga0.47As GaAs MHEMT(渐变组分高电子迁移率晶体管)。从工艺角度,结合器件的小信号等效电路的理论分析,优化了器件T形栅尺寸与工艺,从而减小了器件寄生参数,达到了较好的器件性能。最终制作的In0.52Al0.48As/In0.53Ga0.47As MHEMT饱和电流达到460mA/mm,夹断电压-0.8V,在Vgs为-0.23V时的最大非本征跨导gm为940mS/mm,截止频率ft达到220GHz,最大振荡频率fmax大于200GHz。     

4H-SiC衬底AlGaN/GaN高电子迁移率晶体管的研制

报道了在4H-SiC衬底上AlGaN/GaN高电子迁移率晶体管(HEMT)的研制和室温特性测试结果.器件采用栅长为0.7μm,夹断电压为-3.2V,获得了最高跨导为202mS/mm,最大漏源饱和电流密度为915mA/mm的优良性能和结果.     

4H-SiC衬底AlGaN/GaN高电子迁移率晶体管的研制

报道了在4H-SiC衬底上AlGaN/GaN 高电子迁移率晶体管(HEMT)的研制和室温特性测试结果.器件采用栅长为0.7μm,夹断电压为-3.2V,获得了最高跨导为202mS/mm,最大漏源饱和电流密度为915mA/mm的优良性能和结果.     

硅衬底上生长的MODFET的DC特性和微波频率特性

本文首次报导了用MBE法在硅衬底上生长的1μm栅GaAs/AlGaAs调制掺杂场效应晶体管(MODFET)的微波特性。室温下,硅上这种结构的最大跨导为170mS/mm,GaAs上这种类型结构的跨导为200～250mS/mm,两者性能相当。77K下,在这些结构上没有看到下塌现象,得到的跨导都是270mS/mm。根据室温下微波S参数的测量,在Si上生长的这些GaAs/AlGaAsMODFET的电流增益截止频率为15GHz,它与GaAs衬底上生长的相同器件得到的12～15GHz相当。由高频等效电路模拟,观测到Si和GaAs上生长的所有参数的差别都非常小,这充分证明Si衬底上的GaAs完全适用于做各种器件。     

MBE生长的高质量AlGaAs/InGaAs双δ掺杂PHEMT结构的材料

用MBE方法制备的PHEMT微结构材料,其2DEG浓度随材料结构的不同在2.0-4.0×1012cm-2之间,室温霍耳迁移率在5000-6500cm2·V-1·s-1之间.制备的PHEMT器件,栅长为0.7μm的器件的直流特性:Idss～280mA/mm,Imax～520-580mA/mm,gm～320-400mS/mm,BVDS>15V(Ids＝1mA/mm),BVGS>10V,微波特性:P0～600-900mW/mm,G～6-10dB,ηadd～40-60%;栅长为0.4μm的器件的直流特性:Imax～800mA/mm,gm>400mS/mm.     

AlGaN/GaN HEMT器件的研制

介绍了AlGaN/GaN HEMT器件的研制及室温下器件特性的测试.漏源欧姆接触采用Ti/Al/Pt/Au,肖特基结金属为Pt/Au.器件栅长为1μm,获得的最大跨导为120mS/mm,最大的漏源饱和电流密度为0.95A/mm.     

In0.5Ga0.5As/In0.5Al0.5As应变耦合量子点的形貌和光学性质

提出了利用分子束外延方法生长In0.5Ga0.5As/In0.5Al0.5As应变耦合量子点,并分析量子点的形貌和光学性质随GaAs隔离层厚度变化的特点.实验结果表明,随着耦合量子点中的GaAs隔离层厚度从2 nm增加到10 nm,In0.5Ga0.5As量子点的密度增大、均匀性提高,Al原子扩散和浸润层对量子点PL谱的影响被消除,而且InAlAs材料的宽禁带特征使其成为InGaAs量子点红外探测器中的暗电流阻挡层.由此可见,选择合适的GaAs隔离层厚度形成InGaAs/InAlAs应变耦合量子点将有益于InGaAs量子点红外探测器的研究.     

Donor-acceptor interactions in Al0.5In0.5P

Dopant interactions are considered between Mg-acceptor atoms and various donor species, including the deep donor; oxygen; and the shallow donors, Te, S, and Si, in Al_0.5In_0.5P. While each of these donor species is shown to suppress Mg diffusion and enhance Mg incorporation in Al_0.5In_0.5P, careful analysis of the concentration profiles for these various donor species reveals subtle differences in the shape of the donor and acceptor dopant profiles, suggesting subtle differences in both the type of donor-acceptor interactions involved and in the effectiveness of the various donor species at suppressing Mg diffusion. Oxygen, in particular, is shown to have a profound effect on Mg diffusion in Al_0.5In_0.5P uniform-composition layers, while other donor species are less effective at suppressing Mg diffusion. Such differences suggest that a chemical bonding effect or complex formation may be more dominant between Mg and oxygen, while electrical compensation likely plays a larger relative role between Mg and the shallow-donor species.     

Ohmic contacts ton-type In0.5Ga0.5P

The contact properties of alloyed Ni/Au-Ge/Mo/Au metallization to npoststagger+In_0.5Ga_0.5P epilayers grown by gas-source molecular beam epitaxy on GaAs substrates are reported. A minimum specific contact resistance of 10⁻⁵ Ωcm² was obtained forn = 2 × 10¹⁹ cm⁻³ material after alloying at 360° C for 20 sec. Above this temperature outdiffusion of lattice elements and reactions of the metallization with the In_0.5Ga_0.5P lead to severe morphological changes and degraded contact properties. From the temperature dependence of the contact resistance, thermionic emission was identified as the predominant current transport mechanism in these contacts.     

Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷的介电压电性能

研究了(Na1-xKx)0.5Bi0.5TiO3体系无铅压电陶瓷的介电、压电性能，通过XRD分析，发现随着x的增加，陶瓷的晶体结构由三方相逐渐转变为四方相，x=0．16～0．20范围内具有三方和四方共存相结构，为该体系的准同型相界(MPB)，材料在MPB附近具有最佳的压电性能．测试了陶瓷的介电温谱，表明该体系陶瓷为弛豫型铁电体，电滞回线表明陶瓷在升温过程中发生铁电-反铁电-顺电相变．     

(1-3x)NBT-2xKBT-xBT系无铅压电陶瓷性能研究R&D

通过XRD分析,发现该体系陶瓷都能形成单一的钙钛矿型固溶体,并在0.025≤x≤0.035范围内具有三方和四方共存结构,为该体系的准同型相界。当x=0.035时,陶瓷的压电常数d33达到150 pC/N,平面机电耦合系数kp达到0.297 7,均高于相应两元体系的压电性能。测定了该体系陶瓷材料的介电常数–温度曲线和电滞回线,发现该体系陶瓷的介电温谱都存在两个介电反常峰,分别对应于陶瓷材料的铁电–反铁电和反铁电–顺电相变。同时,该体系陶瓷具有弛豫铁电体性质。     

Ordering and disordering of doped Ga0.5In0.5P

The band gap of Ga_0.5In_0.5P is reported as a function of doping level and growth rate. The lowest band gaps are obtained for hole concentrations of about 2 × 10¹⁷ cm⁻³. For samples doped p-type above 1 × 10¹⁸ cm⁻³, the band gap increases dramatically, regardless of growth rate. This effect is shown to be the result of disordering during growth rather than a change in the equilibrium surface structure with doping. The doping level dependence of the band gap of Ga_0.5In_0.5P samples grown at higher and lower growth rates differs for selenium and zinc doping even though the effects of high doping are the same for both dopants.     

水热法制备纳米Na0.5Bi0.5TiO3粉体

采用Bi(NO3)3?5H2O、Ti(OC4H9)4为原料,在水热条件下研究了影响Na0.5Bi0.5TiO3(BNT)晶体生长和形成的各个影响因素,诸如:水热反应的温度、时间,NaOH浓度以及原料的种类等。实验结果表明,反应温度在160~180℃,保温时间在4~24 h,NaOH浓度为4~12 mol/L时,能制备出纯净的、立方形的纳米Na0.5Bi0.5TiO3晶体,其颗粒线度尺寸为15~55 nm。若温度低于160℃,Na0.5Bi0.5TiO3结晶程度低;若高于180℃,易形成Bi4Ti3O12。当NaOH浓度低于4 mol/L时,Na0.5Bi0.5TiO3晶相少,主要呈Bi4Ti3O12;当其高于12 mol/L时,产物主要是非晶态物质。     

High‐Performance Near‐IR Photodetector Using Low‐Bandgap MA0.5FA0.5Pb0.5Sn0.5I3 Perovskite

Photodetectors with ultrafast response are explored using inorganic/organic hybrid perovskites. High responsivity and fast optoelectronic response are achieved due to the exceptional semiconducting properties of perovskite materials. However, most of the perovskite‐based photodetectors exploited to date are centered on Pb‐based perovskites, which only afford spectral response across the visible spectrum. This study demonstrates a high‐performance near‐IR (NIR) photodetector using a stable low‐bandgap Sn‐containing perovskite, (CH₃NH₃)_0.5(NH₂CHNH₂)_0.5Pb_0.5Sn_0.5I₃ (MA_0.5FA_0.5Pb_0.5Sn_0.5I₃), which is processed with an antioxidant additive, ascorbic acid (AA). The addition of AA effectively strengthens the stability of Sn‐containing perovskite against oxygen, thereby significantly inhibiting the leakage current. Consequently, the derived photodetector shows high responsivity with a detectivity of over 10¹² Jones ranging from 800 to 970 nm. Such low‐cost, solution processable NIR photodetectors with high performance show promising potential for future optoelectronic applications.     

Effects of trimethylindium on the purity of In0.5Al0.5P and In0.5Al0.5as epilayers grown by metalorganic chemical vapor deposition

In_0.5Al_0.5P lattice-matched to GaAs and In_0.5A1_0.5As lattice-matched to InP epilayers were grown by atmospheric pressure metalorganic chemical vapor deposition (AP-MOCVD). The effect of trimethylindium on the purity of the as-grown layers was systematically studied using secondary ion mass spectroscopy (SIMS), deep level transient spectroscopy (DLTS), and capacitance-voltage (C-V) measurements. The SIMS results showed that oxygen is the main impurity in all layers and the oxygen concentration in InAlP was approximately one to four orders of magnitude higher than the oxygen concentration found in InALAs when the same indium source was used, indicating that more oxygen was introduced by the phosphine source than by the arsine source. Two electron traps in the InAlP epilayers and four electron traps in the InALAs epilayers were observed in this study. When a high-purity indium source was used, the best InAlP epilayer showed only one deep electron trap at 0.50 eV while the best InALAs epilayer showed no deep levels measured by DLTS. In addition, we also found that a high concentration of oxygen is related to the high resistivity in both material systems; this suggests that semi-insulating (SI) materials can be achieved by oxygen doping and high quality conducting materials can only be obtained through the reduction of oxygen. The oxygen concentration measured by SIMS in the best InALAs epilayer was as low as 3 × 10¹⁷ cm⁻³.