50 mm×50 mm高性能HgCdTe液相外延材料的批生产技术

采用富碲垂直液相外延技术实现了50 mm×50 mm×3高性能碲镉汞外延材料的制备.外延工艺的样品架采用了三角柱体结构,并设计了防衬底背面粘液的样品夹具.为保证大面积材料的均匀性,工艺中加强了对母液温度均匀性和组分均匀性的控制,50 mm×50 mm外延材料的组分均方差达到了0.000 4,厚度均方差达到了0.4μm.在批量生产技术中,加强了对单轮次生长环境的均匀性和生长轮次之间生长条件一致性的控制,同一轮次生长的3片材料之间的组分偏差小于0.000 4,厚度偏差小于0.1μm,不同生长轮次之间材料的组分之间的波动在±0.002左右,厚度之间的波动在±2μm左右.工艺中对碲锌镉衬底的Zn组分、缺陷尺寸和缺陷密度也加强了控制,以控制大面积外延材料的缺陷,晶体双晶衍射半峰宽(FWHM)小于30弧秒,外延材料的位错密度小于1×105cm~(-2),表面缺陷密度小于5 cm~(-2).外延材料经过热处理后,汞空位型的P型Hg0.78Cd0.22Te外延材料77 K温度下的载流子浓度被控制在8~20×1015cm-3,空穴迁移率大于600 cm2/Vs.材料整体性能和批生产能力已能满足大规模碲镉汞红外焦平面探测器的研制需求.     

MCT薄膜增压LPE生长实验

由于汞压难于控制,碲镉汞液相外延中汞压的控制被认为是该工艺成败的关键之一。用充H_2和附加HgTe控制汞源形成所谓增压液相外延,能够有效地解决汞压控制问题。对此,本文从理论上作以定性的初步探讨,并且用该方法在(111)CdZnTe单晶衬底上外延生长出组分x=0.18的Hg_(1-x)Cd_xTe单晶膜。     

MOCVD法生长HgCdTe/CdTe/GaAs多层异质材料工艺研究

用自已设计的MOCVD设备,国产的DMCd和DETe金属有机源,采用变通的多层互扩散工艺生长了HgCdTe/CdTe/GaAs外延片,获得良好的n型HgCdTe外延层。研究了生长速率与温度的关系;组份与DMCd/DETe之比的关系;x值与汞源温度的关系。生长CdTe和HgCdTe外延层的衬底温度分别约为:370℃和420℃。汞源温度约为280℃,汞压约0.02atm。DMCd/DETe随生长x值不同而不同。气流在2.6～3.7cm/s之间。     

气态源分子束外延AlxGa1-xAs(x=0～1)材料中Si的掺杂行为研究

研究了Si在AlxGa1-xAs(0≤x≤1)中的掺杂行为.为比较Al組份对Si掺杂浓度的影响,在用气态源分子束外延生长(GSMBE)掺Si n型AlxGa1-xAs(0≤x≤1)的所有样品时,n型掺杂剂Si炉的温度恒定不变.用Hall效应测量外延层的自由载流子浓度和迁移率,用X射线双晶衍射迴摆曲线测量外延层的组份.测试结果表明,当AlxGa1-xAs中Al组份从0增至0.38时,Si的掺杂浓度从4×1018cm-3降至7.8×1016cm-3,电子迁移率从1900 cm2/Vs降至100 cm2/Vs.这与AlxGa1-xAs材料的Γ-X直接—间接带隙的转换点十分吻合.在AlxGa1-xAs全组份范囲内,自由载流子浓度隨Al组份从0至1呈“V”形变化,在X=0.38处呈最低点.在x>0.4之后,AlxGa1-xAs的电子迁移随Al组分的增加,一直维持较低值且波动幅度很小.     

用熔体外延法生长的截止波长10μm以上的InAsSb单晶

用熔体外延法,在液相外延系统中,在InAs衬底上成功地生长出了截止波长为11μm的InAsSb单晶.虽然使用液相外延设备,但熔体外延具有不同于液相外延等常规晶体生长方法的创新生长工艺.红外傅里叶光谱测量证明InAsSb材料的截止波长超过10μm.X射线衍射光谱揭示InAsSb外延层具有相当完美的晶体取向结构,且与InAs衬底取向一致,均为(100)方向.霍尔测量结果给出295K下,InAsSb的电子迁移率为4.75×104cm2/Vs,截流子浓度为3.61×1016cm-3;77K下电子迁移率为2.86×104cm2/Vs,载流子浓度为1.50×1016cm-3.数据显示这种材料具有研制新型探测器的良好前景.     

熔体外延法生长的截止波长12 μm的InAs0.04Sb0.96的电学性质

用Van der Pauw法研究了熔体外延(ME)法生长的截止波长为12 μm的InAs0.04Sb0.96单晶电学性质,测量了其电学性质随温度的变化,结果为300 K时,n＝2.3×1016 cm-3,μ＝6×104 cm2/Vs;200 K时,n＝1×1015 cm-3,μ＝1×105 cm2/Vs.分析了石墨舟和石英舟中生长的外延材料不同的电学特性及其散射机理.结果表明,电离杂质散射控制所有样品在低温时的电子输运过程,而高温时材料的电子迁移率主要由极性光学声子的散射过程决定;C的沾污对石墨舟中生长的InAs0.04Sb0.96单晶在200 K以下的电子迁移率有明显的影响.     

截止波长12μm的InAs0.04Sb0.96/GaAs的熔体外延生长及特性研究

用熔体外延(ME)法在半绝缘(100)GaAs衬底上成功生长出了截止波长为12 μm的InAs0.04Sb0.96外延层.傅立叶变换红外(FTIR)透射光谱揭示,InAsSb合金的禁带宽度被强烈变窄.通过分析InAs0.04Sb0.96外延层载流子浓度的温度依存性表明,其室温禁带宽度为0.105 5 eV,与透射光谱测得的数值很好地一致.通过测量12～300 K的吸收光谱,研究了InAs0.04Sb0.96/GaAs的禁带宽度的温度依存性.霍尔测量得出300 K下样品的电子迁移率为4.47×104 cm2/Vs,载流子浓度为8.77×1015 cm-3;77 K下电子迁移率为2.15×104 cm2/Vs,载流子浓度为1.57×1015 cm-3;245 K下的峰值迁移率为4.80×104 cm2/Vs.     

3000V 10A 4H-SiC结型场效应晶体管的设计与制造

介绍了一种常开型高压4H-SiC JFET的仿真与制造工艺。通过仿真对器件结构和加工工艺进行优化,指导下一步的工艺改进。在N+型4H-SiC衬底上生长掺杂浓度(ND)为1.0×1015 cm-3,厚度为50μm的N-外延层,并采用本实验室开发的SiC JFET工艺进行了器件工艺加工。通过测试,当栅极偏压VG=-6V时,研制的SiC JFET可以阻断3 000V电压;当栅极偏压VG=7V、漏极电压VD=3V时,正向漏极电流大于10A,对应的电流密度为100A/cm2。     

激光再结晶和氢退火对多晶硅电学性质的影响

连续Ar+激光再结晶能使多晶硅的电阻率下降,迁移率显著增高,对离子注入剂量为5101151015cm-2的多晶硅经激光再结晶后再进行等离子氢退火,能使其电学性质得到进一步改善,更接近于单晶硅.掺杂浓度为11017cm-3时,电阻率从1.2cm下降到0.45cm,迁移率从 62cm2/Vs增高到 271cm2/Vs,电激活能从 0.03eV下降到-0.007eV,晶界陷阱态密度从3.71011cm-2下降到 1.71011cm-2)。本文在现有多晶硅导电模型的基础上.提出了大晶粒(L=15m)多晶硅的计算公式。结果表明,在掺杂浓度在1101611020cm-3的范围内,理论和实验符合较好。     

改革硅平面晶体管常规工艺的研究

选用超高频小功率晶体管3DG15做工艺研究实验.实验的方法、结果及其分析如下.一、实验方法及结果1.基区低温氧化及硼扩散采用N/N~+型硅外延片:外延层厚度d外=9μ,电阻率ρ外=0.3～0.5Ω·cm,层错密度N层≤300个/cm~2.取Ⅰ、Ⅱ两批片,Ⅰ批片按常规工艺条件氧化,Ⅱ批片接改革工艺条     

P-type as-doping of Hg1−xCdxTe grown by MOMBE

This paper presents a study of both as-grown and annealed p-type Hg_1−xCd_xTe layers that were doped using a cadmium arsenide source. It is shown that by using a metalorganic molecular beam epitaxy system stable and reproducible p-type HgCdTe:As layers were obtained through direct homogeneous doping. The hole concentrations in the as-grown and annealed samples were 8 × 10¹⁶ to 3 × 10¹⁷ cm⁻³ with mobilities of 120∼300 cm²/V-s. The as-grown HgCdTe:As layers had very good crystalline quality with double crystal x-ray rocking curve line-widths ranging from 27 to 42 arc sec. Experimental data demonstrated a strong correlation of hole concentration and mobility with the surface morphology and crystalline quality as a function of Hg flux. The optimum growth window was defined by a narrow range of Hg flux values that gave a smooth film with fewer voids, and higher hole concentrations and mobilities than were obtained at lower or higher Hg fluxes. This correlation between the growth window defined by the surface morphology and the dopant behavior was very important for the successful growth of p-type As-doped HgCdTe materials.     

砷化镓气相外延中Zn的行为和微光材料的制备

在Ga-AsCl_3-H_2系统中用金属Zn为掺杂剂,研究了气相外延GaAs时Zn的掺入和行为。GaAs中Zn的分配系数和空穴浓度分别为10和大于10~(20)cm~(-3),它们都比掺Cd的GaAs大2—3个数量级。这保证了用以制备光阴极材料所需的高空穴浓度的P-GaAs。结合掺Zn和掺s,已重复制得界面良好的P-n结构材料。     

Arsenic Diffusion Study in HgCdTe for Low <Emphasis Type="Italic">p</Emphasis>-Type Doping in Auger-Suppressed Photodiodes

Controllable p-type doping at low concentrations is desired for multilayer HgCdTe samples in a P ⁺/π/N ⁺ structure due to the promise of suppressing Auger processes, and ultimately reduced dark current for infrared detectors operating at a given temperature. In this study, a series of arsenic implantation and annealing experiments have been conducted to study diffusion at low Hg partial pressure with the goal of achieving effective control over dopant profiles at low concentration. Arsenic dopant profiles were measured by secondary ion mass spectroscopy (SIMS), where diffusion coefficients were extracted with values ranging between 3.35 × 10⁻¹⁶ cm² s⁻¹ and 6 × 10⁻¹⁴ cm² s⁻¹. Arsenic diffusion coefficients were found to vary strongly with Hg partial pressure and HgCdTe alloy composition, corresponding to variations in Hg vacancy concentration.     

Dislocation Analysis in (112)B HgCdTe/CdTe/Si

High-quality (112)B HgCdTe/Si epitaxial films with a dislocation density of ??9 × 10⁵ cm^?2 as determined by etch pit density (EPD) measurements have been obtained by thermal cyclic annealing (TCA). The reduction of the dislocation density by TCA has led to a simple rate-equation-based model to explain the relationship between dislocation density and TCA parameters (time, temperature, and number of anneals). In this model, dislocation density reduction is based on dislocation coalescence and annihilation, assumed to be caused by dislocation motion under thermal and misfit stress. An activation energy for dislocation motion in n-type (112)B HgCdTe/Si of 0.93 ± 0.1 eV was determined. This model with no adjustable parameters was used to predict recent TCA annealing results.     

Analysis of Carrier Transport in <Emphasis Type="Italic">n</Emphasis>-Type Hg<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Cd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te with Ultra-Low Doping Concentration

Mercury cadmium telluride (HgCdTe, or MCT) with low n-type indium doping concentration offers a means for obtaining high performance infrared detectors. Characterizing carrier transport in materials with ultra low doping (N_D?=?10¹⁴ cm^?3 and lower), and multi-layer material structures designed for infrared detector devices, is particularly challenging using traditional methods. In this work, Hall effect measurements with a swept B-field were used in conjunction with a multi-carrier fitting procedure and Fourier-domain mobility spectrum analysis to analyze multi-layered MCT samples. Low temperature measurements (77 K) were able to identify multiple carrier species, including an epitaxial layer (x?=?0.2195) with n-type carrier concentration of n?=?1?×?10¹⁴ cm^?3 and electron mobility of μ?=?280000 cm²/Vs. The extracted electron mobility matches or exceeds prior empirical models for MCT, illustrating the outstanding material quality achievable using current epitaxial growth methods, and motivating further study to revisit previously published material parameters for MCT carrier transport. The high material quality is further demonstrated via observation of the quantum Hall effect at low temperature (5 K and below).     

Advanced thermoelectrically cooled midwave HgCdTe focal plane arrays

Midwave HgCdTe diodes and arrays for a 200–230 K operation using thermoelectric (TE) coolers have been fabricated and characterized. The quality of ZnCdTe substrates for the epitaxial growth of HgCdTe layers plays a significant role in determining the performance of the devices. The best diode RoAs at 200 K and 230 K are 1.1×10³ Ω·cm² and 1.6×10² Ω·cm², respectively. Fitting the diode RoAs to analytical equations, the hole lifetime between 230 K and 300 K is found to be on the order of 50 μsec. Arrays in a format of 320×256 have been produced on the HgCdTe layers and imaging pictures have been obtained.     

The interface between Hg1−xCdxTe and its native oxide

The results of a study of the electrical properties of the interface between Hg_1?xCd_xTe with x = 0.21 and its native oxide at 77°K are presented. The native oxide is formed by anodic oxidation and results in an interface with reproducible properties. The surface charge, the surface mobility and the effective lifetime are obtained from galvanomagnetic measurements and are related to the semiconductor bulk parameters, the oxide thickness and the annealing conditions. The surface state charge and the metal-semiconductors work function difference are obtained from the shift of the flat band voltage of metal-oxide-semiconductor (MOS) capacitor characteristics. The interface between Hg_1?xCd_xTe and its native anodic oxide is characterized by a density of fast surface states of the order of 5 × 10¹¹cm^?2 (eV^?1) near the middle of the bandgap. The density of states increases towards the band edges to the order of 10¹³cm^?2 (eV^?1). The measured flat band voltage is approximately ?0.5 V for an oxide thickness of 500 Å and for an n-type semiconductor with an electron carrier concentration in the range 1–3 × 10¹⁵cm^?3 at 77°K. The fixed oxide surface state charge is positive for both p-type and n-type semiconductors and is of the order of 6 × 10¹¹ charges per cm^?2. The surface properties, the significance and the reproducibility of the results are evaluated.     

Influence of laser recrystallization and hydrogen annealing on electrical characteristics of polysilicon

 Asenic ions are implanted with doses of 5×10~(11)—5×10~(15)/cm~2 into LPCVD polysilicon films on SiO_2 isolating substrate.The polysilicon films have been recrystallized with CW Ar~+ laser before implantation.Electrical measurements show that the resistivity is lowered and the mobility is increased significantly at low doping concentration(～10~(17)As~+/cm~3).Plasma hydrogen annealing is performed on laser-recrystallized samples.The electrical characteristics of plasma hydrogen annealed samples are close to that of single crystalline silicon.It is found that the resistivity decreases from 1.2 Ω.cm to 0.45 Ω.cm,the mobility rises from 62 cm~2/V.s to 271 cm~2/V.s,the electrical activation energy reduces from 0.03 eV to -0.007 eV and the trapping state density at the grain boundary drops from 3.7×10~(11)/cm~2 to 1.7×10~(11)/cm~2.Based on the existing theoretical models for conduction in polysilicon, a new formula for large grain polysilicon has been proposed,with the help of which,a good agreement between theory and experimental results is achieved within the doping concentration range from 10~(16)/cm~3 to 10~(20)/cm~3.     

Schottky-barrier capacitance measurements for deep level impurity determination

The time dependence of a Schottky-barrier capacitance due to thermal excitation of trapping centres has been studied. An expression for the junction capacitance is derived which is not restricted to any special range of reverse bias nor to a special relation between shallow and deep impurity concentration. The concentration ratio of shallow to deep centres is calculated from the values of the capacitance at zero and infinite time. From a capacitance vs. time plot the trap emission rate for electrons e_n is obtained. Their energetic level within the forbidden band-gap is determined from the temperature dependence of e_n as well as from the capacitance-time variation. Experimental studies which do confirm the calculations were carried out on gold contacts on oxygen-doped n-type GaAs. Representative results of the investigated samples were: shallow donor density 3 × 10¹⁵ cm^?3, trap density 9·8 × 10¹⁵ cm^?3, electron emission rate 6 × 10^?2 sec^?1, energetic level 0·68 eV and capture cross section 7 × 10^?16 cm².     

Annealing effect on the P-type carrier concentration in low-temperature processed arsenic-doped HgCdTe

We report the results of annealing effects on the As-doped alloy HgCdTe grown by molecular beam epitaxy (MBE), arsenic (As) diffusion in HgCdTe from Hg-rich solutions at low temperatures, and As ion implantation at room temperature. Hall-effect measurements, secondary ion mass spectrometry and p-on-n test photodiodes were used to characterize the As activation. High As-doping levels (10¹⁷−10¹⁹ cm⁻³) could be obtained using either MBE growth, As diffusion or As ion-implantation. Annealed below 400°C, As doping in HgCdTe shows n-type characteristics, but above 410°C demonstrates that all methods of As doping exhibit p-type characteristics independent of As incorporation techniques. For example, for samples annealed at 436°C (P_Hg≈2 atm), in addition to p-type activation, we observe a significant improvement of p/n junction characteristics independent of the As source; i.e. As doping either in situ, by diffusion, or ion implantation. A study of this As activation of As-doped MBE HgCdTe as a function of anneal temperature reveals a striking similarity to results observed for As diffusion into HgCdTe and implanted As activation as a function of temperature. The observed dependence of As activation on partial pressure of Hg at various temperatures in the range of 250 to 450°C suggests that As acts as an acceptor at high Hg pressure (>1 atm) and as a donor at low Hg pressure (<1 atm) even under Hg-rich conditions.