Cl_2/Ar/BCl_3ICP刻蚀AlGaN的研究

感应耦合等离子体(ICP)刻蚀在AlGaN基紫外探测器台面制作中起着重要作用。在对比了ICP与RIE,ECR等干法刻蚀技术优缺点的基础上,采用Ni作为掩膜,Cl2/Ar/BCl3作为刻蚀气体,对金属有机化学气相淀积生长的n-Al0.45Ga0.55N进行了ICP刻蚀研究。刻蚀速率随着ICP直流偏压的增加而增加,刻蚀速率随着ICP功率的增加先增加较快后增加缓慢。最后结合刻蚀表面的扫描电镜(SEM)分析和俄歇电子能谱(AES)深度分析对刻蚀结果进行了讨论。分析表明,在满足刻蚀表面形貌的同时,较低的直流偏压下刻蚀速率较慢,但损伤较小,这对于制备高性能的紫外探测器是有利的。     

Cl2/Ar/BCl3 ICP刻蚀AlGaN的研究

感应耦合等离子体(ICP)刻蚀在AlGaN基紫外探测器台面制作中起着重要作用.在对比了ICP与RIE,ECR等干法刻蚀技术优缺点的基础上,采用Ni作为掩膜,Cl2/Ar/BCl3作为刻蚀气体,对金属有机化学气相淀积生长的n-Al0.45Ga0.55N进行了ICP刻蚀研究.刻蚀速率随着ICP直流偏压的增加而增加,刻蚀速率随着ICP功率的增加先增加较快后增加缓慢.最后结合刻蚀表面的扫描电镜(SEM)分析和俄歇电子能谱(AES)深度分析对刻蚀结果进行了讨论.分析表明,在满足刻蚀表面形貌的同时,较低的直流偏压下刻蚀速率较慢,但损伤较小,这对于制备高性能的紫外探测器是有利的.     

利用CH4/H2/Ar及Cl2高密度等离子体对InSb的高速率刻蚀研究（英文）

利用感应耦合等离子体(ICP)进行了InSb刻蚀研究。为了实现高的刻蚀速率同时保证光滑的刻蚀表面,研究中在CH4/H2/Ar气氛中引入了Cl2。研究发现,对InSb的刻蚀速率随Cl2含量及ICP功率的升高而线性增加。当Cl2含量增加到超过12%或ICP功率大于900 W时,刻蚀表面变得粗糙,而易引起刻蚀损伤的直流偏压随ICP功率的升高而降低。此现象归因于刻蚀副产物InCl3在样品表面的聚集进而妨碍均匀刻蚀反应所致。当样品温度从20℃提高到120℃,刻蚀速率及表面粗糙度无明显变化。通过试验研究,实现了对InSb的高速率、高垂直度刻蚀,刻蚀速率大于500 nm/min,对SiO2掩模刻蚀选择比大于6,刻蚀表面光洁,刻蚀垂直度可达80°。     

高Al组分AlGaN的ICP干法刻蚀

初步研究了采用Cl2 /Ar /He等离子体对MOCVD生长的背照射Al0. 45 Ga0. 55N材料的 ICP干法刻蚀工艺。采用离子束溅射生长的Ni作为刻蚀掩模,刻蚀速率随ICP直流偏压的增加而增加。采用传输线模型测量了刻蚀前后AlGaN材料方块电阻的变化,分析了干法刻蚀电学损伤与直流偏压的关系。用扫描电镜( SEM)观察了不同直流偏压下刻蚀台面形貌,并对其进行了分析。     

InGaAs探测器制备的ICP刻蚀方法研究

采用Cl2/BCl3/Ar感应耦合等离子体对InP/In0.55Ga0.45As/InP进行了刻蚀。讨论了不同的气体组分、ICP功率、直流自偏压下对刻蚀速率、表面粗糙度的影响。初步得到了一种稳定、刻蚀表面清洁光滑、图形轮廓良好、均匀性好和刻蚀速率较高的工艺。利用此工艺制作的8元InP/In0.55Ga0.45As/InP(PIN)探测器,峰值探测率为1.04×1012cmHz1/2W-1。     

基于ICP刻蚀GaN选择比的研究

在干法刻蚀GaN时使用AZ-4620作为掩膜层,为了在较快的GaN刻蚀速率下获得良好的GaN/AZ-4620刻蚀选择比,使用电感耦合等离子刻蚀机（ICP）,运用Cl2和BCl3作为刻蚀气体,改变气体总流量、直流自偏压、ICP功率、气体组分等工艺条件,并讨论了这些因素对GaN/AZ-4620刻蚀选择比以及对GaN刻蚀速率的影响。实验结果获得了GaN在刻蚀速率为225nm/min时的GaN/AZ-4620选择比为0.92,可以应用于实际生产。     

GaN/SiO_2刻蚀选择比的研究

在干法刻蚀GaN时使用SiO2作为掩蔽物,为了在较快的GaN刻蚀速率下获得良好的GaN/SiO2刻蚀选择比,使用电感耦合等离子刻蚀机(ICP),运用Cl2和Ar作为刻蚀气体,改变ICP功率、直流自偏压、气体总流量、气体组分等工艺条件,并讨论了这些因素对GaN/SiO2刻蚀选择比以及对GaN刻蚀速率的影响。实验结果获得了GaN在刻蚀速率为165nm/min时的GaN/SiO2选择比为8∶1。设备验收时GaN刻蚀速率为70nm/min,GaN/SiO2选择比为3.5∶1,可以应用于实际生产。     

高密度RF等离子体刻蚀工艺直流自我偏压的研究

直流自我偏压作为高密度射频(RF)等离子体刻蚀工艺中的重要电学参数,反映出具有高能量的离子对待刻蚀晶片的轰击效果,后者决定了刻蚀工艺的各向异性、刻蚀速率、选择比及形貌特征等工艺结果。该文以HBr作为刻蚀气体,采用电感耦合等离子体(ICP)金属刻蚀系统针对刻蚀工艺中的直流自我偏压进行研究。研究中分别改变离子源功率、衬底偏压功率、刻蚀压力及HBr气体流量,观察直流自我偏压及其峰值的相应变化规律。实验结果表明,随着离子源功率的升高,直流自我偏压将会轻度降低;升高偏压功率则会显著提升直流自我偏压。刻蚀压力与直流自我偏压呈正比例关系,HBr气体流量的变化及待刻蚀晶片的材质对直流自我偏压无显著影响。     

Cl2／Ar／BCl3ICP刻蚀对AIGaN的损伤研究

感应耦合等离子体（ICP）刻蚀在AlGaN基紫外探测器台面制作中起着重要作用，初步研究了Cl2／Ar／BCl3ICP刻蚀对A1GaN材料的损伤。运用X射线光电子能谱（XPS）对ICP刻蚀前后的n型Al0.45Ga0．55N表面进行了分析，并对刻蚀后AlGaN材料在N2气中快速热退火进行了研究。结果表明，在N2气中550℃退火3min对材料的电学性能有明显的改善作用。     

Cl_2/Ar/BCl_3 ICP刻蚀对AlGaN的损伤研究

感应耦合等离子体(ICP)刻蚀在AlGaN基紫外探测器台面制作中起着重要作用,初步研究了Cl2/Ar/BCl3ICP刻蚀对AlGaN材料的损伤。运用X射线光电子能谱(XPS)对ICP刻蚀前后的n型Al0.45Ga0.55N表面进行了分析,并对刻蚀后AlGaN材料在N2气中快速热退火进行了研究。结果表明,在N2气中550°C退火3 min对材料的电学性能有明显的改善作用。     

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.     

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。     

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.     

The C-V-f and G/ω-V-f characteristics of Al/SiO2/p-Si (MIS) structures

The frequency dependence of capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of the Al/SiO₂/p-Si metal-insulator-semiconductor (MIS) structures has been investigated taking into account the effect of the series resistance (R_s) and interface states (N_ss) at room temperature. The C-V and G/ω-V measurements have been carried out in the frequency range of 1 kHz to 1 MHz. The frequency dispersion in capacitance and conductance can be interpreted only in terms of interface states and series resistance. The N_ss can follow the ac signal and yield an excess capacitance especially at low frequencies. In low frequencies, the values of measured C and G/ω decrease in depletion and accumulation regions with increasing frequencies due to a continuous density distribution of interface states. The C-V plots exhibit anomalous peaks due to the N_ss and R_s effect. It has been experimentally determined that the peak positions in the C-V plot shift towards lower voltages and the peak value of the capacitance decreases with increasing frequency. The effect of series resistance on the capacitance is found appreciable at higher frequencies due to the interface state capacitance decreasing with increasing frequency. In addition, the high-frequency capacitance (C_m) and conductance (G_m/ω) values measured under both reverse and forward bias were corrected for the effect of series resistance to obtain the real diode capacitance. Experimental results show that the locations of N_ss and R_s have a significant effect on electrical characteristics of MIS structures.     

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.     

Temperature dependent current-voltage characteristics of n-MgxZn1−xO/p-GaN junction diodes

This study investigates the temperature dependence of the current-voltage (I-V) characteristics of n-Mg_xZn_1−xO/p-GaN junction diodes. The n-Mg_xZn_1−xO films were deposited on p-GaN using a radio-frequency (rf) magnetron sputtering system followed by annealing at 500, 600, 700, and 800 °C in nitrogen ambient for 60 s, respectively. The n-Mg_xZn_1−xO/p-GaN diode at a substrate temperature of 25 °C had the lowest leakage current in reverse bias. However, the leakage current of the diodes increased with an increase in annealing temperatures. The temperature sensitivity coefficients of the I-V characterizations were obtained at different substrate temperatures (25, 50, 75 100, and 125 °C) providing extracted values of 26.4, 27.2, 17.9, and 0.0 mV/°C in forward bias and 168.8, 143.4, 84.6, and 6.4 mV/°C in reverse bias, respectively. The n-Mg_xZn_1−xO/p-GaN junction diode fabricated with Mg_xZn_1−xO annealed at 800 °C demonstrated the lowest temperature dependence. Based on these findings, the n-Mg_xZn_1−xO/p-GaN junction diode is feasible for GaN-based heterojunction bipolar transistors (HBTs).     

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.     

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.     

M／PS／Si／M结构的电致发光

用阳极氧化工艺制作了多孔硅膜，采用第二次阳极氧化的方法看到了多孔硅的电致发光现象，并制作了一个Ｍ／ＰＳ／Ｓｉ／Ｍ类肖特基结构的发光二极管，观察到其电致发光，但其电致发光效率与强度很低，寿命很短，提出了研制实用化的多孔硅电致发光器件的努力方向。