电流增益截止频率为441 GHz的InGaAs/InAlAs InP HEMT

本文设计并制作了f_T > 400 GHz的In_0.53Ga_0.47As/In_0.52Al_0.48As 铟磷高电子迁移率晶体管（InP HEMT）。采用窄栅槽技术优化了寄生电阻。器件栅长为54.4 nm,栅宽为2 × 50 μm。最大漏极电流I_DS.max为957 mA/mm,最大跨导g_m.max为1265 mS/mm。即使在相对较小的V_DS = 0.7 V下,电流增益截止频率f_T达到了441 GHz,最大振荡频率f_max达到了299 GHz。该器件可应用于太赫兹单片集成放大器和其他电路中。     

具有低噪声及高线性度的高性能MOCVD-SiNx/AlN/GaN 毫米波MIS-HEMTs

文章在超薄势垒AlN/GaN异质结构上采用金属有机化学气相沉积（MOCVD）原位生长SiN_x栅介质,成功制备了高性能的SiN_x/AlN/GaN金属-绝缘体-半导体高电子迁移率晶体管（MIS-HEMTs）。深能级瞬态谱（DLTS）技术测试SiN_x/AlN的界面信息,显示其缺陷能级深度为0.236 eV,俘获截面为3.06×10^-19 cm^-2,提取的界面态密度为10¹⁰~10¹² cm^-2eV^-1,表明MOCVD原位生长的SiN_x可以有效降低界面态。同时器件表现出优越的直流、小信号和噪声性能。栅长为0.15 μm的器件在2 V的栅极电压（V_gs）下具有2.2 A/mm的最大饱和输出电流,峰值跨导为506 mS/mm,最大电流截止频率（f_T）和最大功率截止频率（f_MAX）分别达到了65 GHz和123 GHz,40 GHz下的最小噪声系数（NF_min）为1.07 dB,增益为 9.93 dB。V_ds = 6 V时对器件进行双音测试,器件的三阶交调输出功率（OIP3）为32.6 dBm,OIP3/P_dc达到11.2 dB。得益于高质量的SiN_x/AlN界面,SiN_x/AlN/GaN MIS-HEMT显示出了卓越的低噪声及高线性度,在毫米波领域具有一定的应用潜力。     

分子束外延高铟组分InGaAs薄膜研究

研究了分子束外延生长条件对高铟组分InGaAs材料性能的影响,分析了生长温度、V/III比和As分子束形态对In_0.74Ga_0.26As材料光致发光和X射线衍射峰强度、本底载流子浓度和迁移率的影响。测试结果表明：适中的生长温度和V/III比可以提高材料晶格质量,减少非辐射复合,降低本底杂质浓度。As分子束为As₂时In_0.74Ga_0.26As材料质量优于As₄分子束。当生长温度为570 ℃,As分子束形态为As₂,V/III比为18时,可以获得较高的光致发光和X射线衍射峰强度,室温和77 K下的本底载流子浓度分别达到6.3×10¹⁴ cm^-3和4.0×10¹⁴ cm^-3,迁移率分别达到13 400 cm²/Vs和45 160 cm²/Vs。     

渠道火花烧蚀法制备In2O3∶Mo透明导电薄膜

采用渠道火花烧蚀技术在普通玻璃基板上制备了掺钼氧化铟In₂O₃∶Mo透明导电薄膜，研究了烧蚀时氧气压强对薄膜光电性能的影响. 在基板温度Ts=350℃时，薄膜的电阻率和载流子浓度随氧气压强增大分别呈凹形和凸形的变化趋势. 薄膜电阻率最小值是4.8e-4Ω·cm，载流子浓度为7.1e20cm^-3. 载流子迁移率最高可达49.6cm²/ (V·s) . 可见光区域平均透射率大于87%以上，由紫外光电子谱分析得到薄膜的表面功函数为4.6eV. X射线衍射分析表明，薄膜结晶性良好并在（222）晶面择优取向生长. 原子力显微镜观察薄膜样品表面得到方均根粗糙度为0.72nm,平均粗糙度为0.44nm，峰谷最大差值为15.4nm.     

（英）数字递变异变赝衬底上2.6 μm In0.83Ga0.17As/InP光电探测器的性能改进

本文研究了In_0.83Al_0.17As/In_0.52Al_0.48As数字递变异变缓冲层结构(DGMB)的总周期数对2.6 μm延伸波长In_0.83Ga_0.17As光电二极管性能的影响。实验表明,在保持总缓冲层厚度不变的情况下,通过将在InP衬底上生长的In_0.83Al_0.17As/In_0.52Al_0.48As DGMB结构的总周期数从19增加到38,其上所生长的In_0.83Ga_0.17As/In_0.83Al_0.17As光电二极管材料层的晶体质量得到了显著改善。对于在总周期数为38的DGMB上外延的In_0.83Ga_0.17As光电二极管,观察到其应变弛豫度增加到99.8％,表面粗糙度降低,光致发光强度和光响应度均增强,同时暗电流水平被显著抑制。这些结果表明,随着总周期数目的增加,DGMB可以更有效地抑制穿透位错的传递并降低残余缺陷密度。     

SiNx/SiOxNy叠层结构防潮能力的研究

研究了等离子体增强化学气相沉积(PECVD)工艺参数对SiN_x及SiO_xN_y防潮能力的影响,并测试了SiN_x/SiO_xN_y叠层薄膜的水汽渗透速率(WVTR)。实验结果表明:单层SiN_x薄膜和SiO_xN_y薄膜都存在临界厚度,当膜厚大于临界值时,继续增大厚度不会明显改善薄膜的WVTR。当沉积温度从50℃提高到250℃,SiN_x薄膜的WVTR从0.031g/(m²·day)降至0.010g/(m²·day)。SiO_xN_y沉积时,增大N₂O通入量对薄膜的WVTR影响不明显,但可以有效改善薄膜的弯曲性能。最后,4个SiN_x/SiO_xN_y叠层膜的WVTR下降到了4.4×10-4g/(m²·day)。叠层膜防潮能力的显著提升归因于叠层结构可以有效解耦层与层之间的缺陷,延长水汽渗透路径。     

Population inversion between Γ subbands in quantum wells under the conditions of Γ-<Emphasis Type="Italic">L</Emphasis> intervalley transfer

Monte Carlo simulations of electron transport in Al_xGa_1−x As/GaAs/In_yGa_1−y As double-quantum-well heterostructures in high lateral electric fields are carried out. It is shown that, under the conditions of intervalley Γ-L electron transfer, there exists a population inversion between the first and the second quantum-confinement subbands in the Γ valley. The population inversion appears in the fields exceeding 4 and 5.5 kV/cm at 77 and 300 K, respectively. The gain in a superlattice composed of such quantum wells is estimated to be on the order of 100 cm⁻¹ for radiation with a wavelength of 12.6 μm. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 37, No. 2, 2003, pp. 224–229. Original Russian Text Copyright ? 2003 by Aleshkin, Andronov, Dubinov.     

用热蒸发法制备的Cu2ZnSnS4 薄膜的光电性能

在室温下用真空热蒸发法在玻璃基片上制备Sn/Cu/ZnS 前躯体膜层,然后对其在550C 下在硫气氛中硫化3小时以制得Cu₂ZnSnS₄ (CZTS) 多晶薄膜。对该薄膜进行X射线衍射（XRD）、能量色散X射线光谱（EDX）、紫外可见近红外分光光度计、霍尔测量系统和3D光学显微镜等分析测试。实验结果表明,当[Cu]/([Zn] [Sn]) =0.83和[Zn]/[Sn] =1.15时,该CZTS薄膜在光子能量范围在1.5 - 3.5 eV 时其吸收系数大于4.010₄cm_-1 ,直接带隙为1.47 eV。其载流子浓度、电阻率和迁移率分别为7.9710₁₆ cm_-3, 6.06 Ω.cm, 12.9 cm₂/(V.s), 导电类型为p型。因此,所制备出的CZTS 薄膜适合作为太阳电池的吸收层材料。     

High density 2DEG in III-V semiconductor heterostructures and high-electron-mobility transistors based on them

Situation in high-electron-mobility transistor (HEMT) technology is discussed. The N-AlGaAs/InGaAs/GaAs pseudomorphic HEMT’s are now considered as most advanced for mmwave monolithic circuits, but metamorphic N-In_xAl_1−x As/In_yGa_1−y As/In_xAl_1−x As HEMT’s grown on GaAs substrates are very promising for the future high-frequency devices. High density 2DEG in HEMT’s is analyzed by means of the Hall effect and photoluminescence measurements. Processing technology of the sub-0.25-μm pseudomorphic HEMT’s, metamorphic HEMT’s and their characteristics are also described. Fiz. Tekh. Poluprovodn. 33, 1064–1065 (September 1999) This article was published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

截止波长2.2 µm的平面型延伸波长InGaAs探测器

采用闭管扩散的方法成功研制了截止波长2.2 μm的平面型延伸波长InGaAs探测器芯片。在分子束外延法（MBE）生长的In_0.75Al_0.25As/ In_0.75Ga_0.25As/ In_0.75Al_0.25As外延材料上,采用砷化锌作为扩散掺杂源、SiN_x作为扩散掩膜层,实现了扩散成结。分析了扩散结深和载流子侧向收集宽度、I-V特性、光谱响应特性和探测率,结果表明：150 K温度下,器件暗电流密度0.69 nA/cm²@-10 mV,响应截止波长和峰值波长分别为2.12 μm和1.97 μm,峰值响应率为1.29 A/W,峰值量子效率达82%,峰值探测率为1.01×10¹² cmHz^1/2/W。这些结果对后续进一步优化平面型延伸波长InGaAs焦平面探测器有重要的指导意义。     

Morphological and electrical characterization of SixCryCzBv thin films

Si_xCr_yC_zB_v thin films with several compositions have been studied for integration of high precision resistors in 0.8 μm BICMOS technology. These resistors, integrated in the back-end of line, have the advantage to provide high level of integration and attractive electrical behavior in temperature, for analog devices. The film morphology and the structure have been investigated through transmission electron microscopy analysis and have been then related to the electrical properties on the base of the percolation theory. According to this theory, and in agreement with experimental results, negative thermal coefficient of resistance (TCR) has been obtained for samples with low Cr content, corresponding to a crystalline volume fraction below the percolation threshold.Samples with higher Cr content exhibit, instead, a variation of the TCR as a function of film thickness: negative TCR values are obtained for thickness lower than 5 nm, corresponding to a crystalline volume fraction below the percolation threshold; positive TCR are obtained for larger thickness, indicating the establishment of a continuous conductive path between the Cr rich grains. This property seems to be determinant in order to assure the possibility to obtain thin film resistors almost independent on the temperature.     

Thermoelectric Properties of Triple-Filled BaxYbyInzCo4Sb12 Skutterudites

Indium-filled skutterudites are promising power generation thermoelectric materials due to the presence of an InSb nanostructure that lowers the thermal conductivity. In this work, we have investigated thermoelectric properties of triple-filled Ba _x Yb _y In _z Co₄Sb₁₂ (0 ≤ x, y, z ≤ 0.14 actual) compounds by measuring their Seebeck coefficient, electrical conductivity, thermal conductivity, and Hall coefficient. All samples were prepared by a melting–annealing–spark plasma sintering method, and their structure was characterized by x-ray diffraction and transmission electron microscopy (TEM). TEM results show the development of an InSb nanostructure with a grain size of 30 nm to 500 nm. The nanostructure is present in all samples containing In and is also detected by specific heat measurements. The Seebeck and Hall coefficients indicate that the compounds are n-type semiconductors. Electrical conductivity increases with increasing Ba content. Thermal conductivity is strongly suppressed upon the presence of In in the skutterudite structure, likely due to enhanced boundary scattering of phonons on the nanometer-scale InSb inclusions. The highest thermoelectric figure of merit is achieved with Ba_0.09Yb_0.07In_0.06Co₄Sb_11.97, reaching ZT = 1.25 at 800 K.     

Broadband microwave noise characteristics of high-linearity composite-channel Al/sub 0.3/Ga/sub 0.7/N/Al/sub 0.05/Ga/sub 0.95/N/GaN HEMTs

We report broadband microwave noise characteristics of a high-linearity composite-channel HEMT (CC-HEMT). Owing to the novel composite-channel design, the CC-HEMT exhibits high gain and high linearity such as an output third-order intercept point (OIP3) of 33.2 dBm at 2 GHz. The CC-HEMT also exhibits excellent microwave noise performance. For 1-/spl mu/m gate-length devices, a minimum noise figure (NF/sub min/) of 0.7 dB and an associated gain (G/sub a/) of 19 dB were observed at 1 GHz, and an (NF/sub mi/) of 3.3 dB and a G/sub a/ of 10.8 dB were observed at 10 GHz. The dependence of the noise characteristics on the physical design parameters, such as the gate-source and gate-drain spacing, is also presented.     

Effect of Mg doping on the superconducting properties of Cu/sub 1-x/Tl/sub x/Ba/sub 2/Ca/sub 3-y/Mg/sub y/Cu/sub 4/O/sub 12-/spl delta//

Superconducting properties of Cu/sub 1-x/Tl/sub x/Ba/sub 2/Ca/sub 3-y/Mg/sub y/Cu/sub 4/O/sub 12-/spl delta// (Cu/sub 1-x/Tl/sub x/Mg/sub y/-1234) material have been studied in the composition range y=0,1.5,2.25. The zero resistivity critical temperature [T/sub c/(R=0)] was found to increase with the increased concentration of Mg in the unit cell; for y=1.5 [T/sub c/(R=0)]=131 K was achieved which is hitherto highest in Cu/sub 1-x/Tl/sub x/-based superconductors. The X-ray diffraction analyses have shown the formation of a predominant single phase of Cu/sub 0.5/Tl/sub 0.5/Ba/sub 2/Ca/sub 3-y/Mg/sub y/Cu/sub 4/O/sub 12-/spl delta// superconductor with an inclusion of impurity phase. It is observed from the convex shape of the resistivity versus temperature measurements that our as-prepared material was in the region of carrier over-doping, and the number of carriers was optimized by postannealing experiments in air at 400/spl deg/C, 500/spl deg/C, and 600/spl deg/C. The T/sub c/(R=0) was found to increase with postannealing and the best postannealing temperature was found to be 600/spl deg/C. The mechanism of increased T/sub c/(R=0) is understood by carrying out infrared absorption measurements. It was observed through softening of Cu(2)-O/sub A/-Tl apical oxygen mode that improved interplane coupling was a possible source of enhancement of T/sub c/(R=0) to 131 K.     

Pseudomorphic In/sub 0.52/Al/sub 0.48/As/In/sub 0.7/Ga/sub 0.3/As HEMTs with an ultrahigh f/sub T/ of 562 GHz

We fabricated decananometer-gate pseudomorphic In/sub 0.52/Al/sub 0.48/As/In/sub 0.7/Ga/sub 0.3/As high-electron mobility transistors (HEMTs) with a very short gate-channel distance. We obtained a cutoff frequency f/sub T/ of 562 GHz for a 25-nm-gate HEMT. This f/sub T/ is the highest value ever reported for any transistor. The ultrahigh f/sub T/ of our HEMT can be explained by an enhanced electron velocity under the gate, which was a result of reducing the gate-channel distance.     

Electrical behavior of double heterojunction NpNGaAlAs/GaAs/GaAlAs bipolr transistors

This paper deals with a theoretical and experimental study of double heterojunction NpN GaAlAs/GaAs/GaAlAs bipolar transistors fabricated by liquid phase epitaxy. Starting from the general transport equations of the macroscopic theory of diffusion, a charge-control-type model is first established. The compact analytical expressions which determine the transfer characteristics (J_C′V_BE) and intrinsic current gain $\text{h}{}_{\mathrm{FE}}{}^1$ are expressed as a function of the technological or geometrical parameters of the structure. A study of the sensitivity to these parameters highlights in particular the influence of the zone including the conduction band spike of the base collector heterojunction. Such an influence may assume the form of a substantial degradation of the device's electrical characteristics (reduction of the base transfer factor, increase in transit time). The experimental behavior observed on characterized devices confirms the theoretical predictions.     

Current-voltage characteristics of GaAs p-i-n and n-i-n diodes

Using the same basic equations as Kazarinov et al.[2], but assuming that the product of the electron drift velocity and of the electron lifetime remains constant, we have derived a new formula for the forward d.c. current—voltage characteristic distinguished by the saturated voltage. We have shown that this formula can describe the measured characteristics of some GaAs p-i-n and n-i-n diodes.     

Ta/NiFe/Cu/NiFe/FeMn/Ta自旋阀多层膜的X射线光电子能谱的研究

实验表明：Ta／NiFe／FeMn／Ta多层膜的交换耦合场(Hex)要大于Ta／NiFe／Cu／NiFe／FeMn／Ta自旋阀多层膜中的以Hex。为了寻找其原因，用X射线光电子能谱(XPS)研究了Ta(12nm)／NiFe(7nm)，Ta(12nm)／NiFe(7nm))／Cu(4nm)和Ta(12nm)／NiFe(7nm)／Cu(3nm)／NiFe(5nm)3种样品，研究结果表明，前两种样品表面无任何来自下层的元素偏聚；但在第3种样品最上层的NiFe表面上，探测到从下层偏聚上来的Cu原子。我们认为：Cu在NiFe／FeMn层间的存在是Ta／NiFe／Cu／NiFe／FeMn／Ta自旋阀多层膜的Hex低于Ta／NiFe／FeMn／Ta多层膜Hex的一个重要原因。     

Analytical solution of the state-dependent Erlangian queue: M/Ej/1/N with balking

The objective of this paper is to derive the analytical solution of the truncated single-channel Erlangian queue M/E_j/1/N with balking and state-dependent service rate. The researcher deduces p_ns the probability of n units in the system (n = 1, 2, 3,…, N) and the customer in service being in phase backwards, i.e. j is the first phase of service and 1 is the last (a customer leaving phase 1 actually leaves the system). p₀ is the probability of an empty system by using the iterative method. At the end of this paper some special cases are obtained.     

Device linearity comparison of uniformly doped and /spl delta/-doped In/sub 0.52/Al/sub 0.48/As/In/sub 0.6/Ga/sub 0.4/As metamorphic HEMTs

The uniformly doped and the /spl delta/-doped In/sub 0.52/Al/sub 0.48/As/In/sub 0.6/Ga/sub 0.4/As metamorphic high-electron mobility transistors (MHEMTs) were fabricated, and the dc characteristics and the third-order intercept point (IP3) of these devices were measured and compared. Due to more uniform electron distribution in the quantum-well region, the uniformly doped MHEMT exhibits a flatter transconductance (G/sub m/) versus drain-to-source current (I/sub DS/) curve and much better linearity with higher IP3 and higher IP3-to-P/sub dc/ ratio as compared to the /spl delta/-doped MHEMT, even though the /spl delta/-doped device exhibits higher peak transconductance. As a result, the uniformly doped MHEMT is more suitable for communication systems that require high linearity operation.