电离辐照和隧道注入实验引起氧化层电荷以及界面态的产生

本文将讨论MOS电容中辐照及高电场隧道注入的实验结果。与辐照剂量有关的禁带中央电压的漂移仅仅是由空穴俘获引起。在隧道注入的情况下,由碰撞离子化引起的电子-空穴对的产生需要很大的电子密度和强电场。因此,所建立的电荷产生模型考虑到了中性氧化层中的空穴俘获,其次考虑了在带正电的状态中的电子俘获以及被俘获的电子的排空。利用这种模型,只要精确地知道了碰撞离化系数α,就能够对MOS器件的抗核辐照强度进行预测。假如不是这种情况,则需利用电离辐照和隧道注入的混合技术来确定与电场强度F相关的碰撞电离系数α=α_0 exp(-Hα/F)。利用实验结果与该模型相拟合的方法,就可分别导出电子俘获截面σn和排空截面βn,得到σn依赖于F~(-3)和βn依赖于exp(-Hβ/F)的关系。发现工艺参数的变化对其影响是很小的。提出的这个模型是通过一系列的辐照和注入实验验证的。氧化层电荷的产生伴随界面态密度分布的增加,在两种实验中,它的峰值是在禁带中央之上约0.15eV处。结果表明,界面态的产生与俘获的空穴数成正比。注入实验得到了如下的界面态类型,受主型界面态在禁带中央之上,施主型界面态在禁带中央之下。这进一步证实了禁带中央电压的变化是判断氧化层电荷变化的分类点,因为在禁带中央,界面态变成中性的了。     

金属-二氧化硅-半导体(MOS)结构的电子辐照效应

金属.二氧化硅-半导体(MOS)结构对于SiO2-Si界面非常敏感,能够方便地反映出氧化层电荷、界面态密度等参数.为了研究MOS结构的电子辐照效应,采取了能量为0.8 MeV,辐照剂量范围为2×1013～1×1014cm-2屯的电子束作为辐照源.实验发现,MOS结构经电子辐照后,在SiO2-Si界面处引入界面态,并且在二氧化硅内部积累正电荷.通过对MOS结构在电子辐照前后高、低频C-V曲线的测试,测试出辐照在氧化层引入的界面态密度达到了1014cm-2eV-1,而积累的正电荷面密度达到了10-2cm-2.同时得到了界面态密度和积累电荷密度与辐照剂量的关系.     

MOS电容的热载流子损伤及其与电离辐射损伤的关系

通过对国产加固 N型 MOS电容进行衬底热电子高场注入 ( SHE)及 γ总剂量辐照实验 ,特别是进行总剂量辐射损伤后的热载流子损伤叠加实验 ,从微观氧化物电荷、界面态的感生变化及其界面态的能量分布变化等角度研究比较了 MOS结构热载流子损伤特性及与电离辐射损伤的关系。     

注氟加固PMOSFET的电离辐射响应与时间退火效应

研究了注F加固PMOSFET的总剂量辐照响应特性和辐照后由氧化物电荷、界面态变化引起的阈电压漂移与时间、温度、偏置等退火条件的关系，发现一定退火条件下注F加固PMOSFET由于界面态密度、特别是氧化物电荷密度继续增加，使得电路在电高辐照后继续损伤，探讨了加速MOS器件电离辐照感生界面态生长的方法。     

用真空紫外辐照研究Si-SiO_2界面的氧化层陷阱和界面态

以氦灯真空紫外光源研究了辐照下 n(100)硅衬底MOS样品的氧化层陷阱和Si-SiO_2界面态.发现在湿氧和干氧氧化层中都存在密度为10~(12)/cm~2数量级的空穴陷阱,部分氧化层中有密度为10~(11)/cm~2的受主型电子陷阱.湿氧样品在正偏置和零偏置辐照后出现具有确定能级(E_c-E_s(?)0.40eV)的界面态密度宽峰.辐照引进的界面态和空穴被陷阱俘获有关,在1×10~(10)～5 × 10~(11)cm~(-2)·eV~(-1)范围,禁带中央界面态密度正比于被俘获空穴的密度.辐照产生的界面态不能由电子注入加以消除.本文由空穴俘获-弱键破裂模型讨论了实验结果.     

n—GaAs Ti／Mo／Ti／Au肖特基势垒接触失效机理的研究

为了弄清界面态、电徙动、界面扩散及反应对肖特基势垒接触和器件电学特性的影响,我们对以Ti/Mo/Ti/Au作为栅金属的GaAs MESFET进行了四种不同的应力试验:1.常温反偏(HRB)。2.高温反偏(HTRB)。3.高温正向大电流(HFGC)。4.高温贮存(HTS)。HRB试验中从0.64eV减少到0.62eV,理想因子n略有增大。HTS试验中Φ_b从0.67eV增加到0.69eV。分析表明,这归因于界面氧化层的消失,以及Ti与GaAs的反应;HFGC试验结果表明其主要的失效模式为烧毁,其次为电徙动及断栅现象。AES分析表明,应力试验后的样品,其肖特基势垒接触界面发生模糊,有明显的互扩散和反应发生。     

Cu-GaAs(110)界面的同步辐射光电子谱研究

本文用同步辐射光电子谱研究了在室温n型GaAs(110)解理面上蒸发淀积的Cu-GaAs(110)界面和肖特基势垒的形成.Ga3d和As3d光电子谱随Cu的厚度的变化表明:在小于0.5单原子层(ML)Cu时只观察到能带的刚性弯曲,并无明显的界面反应;在大于1MLCu时出现明显的界面反应,形成处于界面的金属Ga和处于Cu表面的As;Cu有岛状生长的迹象.由谱分解的结果确定了在3—60A Cu范围内界面费米能级的位置在导带底以下约0.9eV处.肖特基势垒在0.5MLCu时已大部分(～80％)形成,在3MLCu时就完全形成.讨论了Cu-GaAs(110)界面和肖特基势垒形成的机制.     

HCl氧化物MOS结构质子辐照诱导的界面陷阱效应

用微分电容法研究质子辐照HCl氧化物铝栅MOS结构诱导的界面陷阱,栅氧化层在1 160℃很干燥的、含0～10％HCl的气氛中热生长而成,质子辐照能量为120～300keV,注入总剂量范围为8×10~(13)～1×10~(16)p/cm~2。结果表明,辐照诱导的界面陷阱能级密度随质子能量、剂量增加而增加。然而,氧化层中掺入6％HCl时,辐照诱导的界面陷阱明显减少。这样,已能有效地改变MOS器件的抗辐照性能。实验结果可用H~+二级过程解释。     

高剂量辐照条件下的MOSFET总剂量辐照效应模型

报道了一种用于在高剂量辐照条件下MOS器件抗辐照电路模拟的半经验模型.利用该模型对MOS器件实验结果进行了模拟,模型计算结果与实验吻合较好.初步分析了高剂量条件下不同散射机制对模拟结果的影响,结果表明界面电荷的库仑散射是引起电子迁移率退化的主要机制.     

MOS结构的软X射线辐射损伤

本文报道了MOS结构受软X射线辐照的辐射损伤的研究结果.指出,软X射线辐照将引起了 SiO_2层中正电荷及SiO_2-Si界面界面态密度的增加,而且在SiO_2体内形成电子陷阱和中性陷阱.文中还报道了辐射损伤的退火结果.     

Material reactions and barrier height variations in sintered AlInP Schottky diodes

Significant increases in the AlInP Schottky barrier have been obtained by process modification of the metal-semiconductor interface. The resultant barrier height increases (from 0.3 to 0.6 eV) are due to oxygen build-up at the interface, in the form of P₂O₅. Auger electron spectroscopy studies of the metal-semiconductor interface indicate an excellent correlation between barrier height increases and oxygen build-up at the AlInP interface.     

Model calculations for metal-insulator-semiconductor solar cells

An analytical approach to calculating MIS solar cell properties has been formulated and utilized to study solar cell efficiency as a function of interfacial layer thickness, various interfacial film parameters and band gap. Three models are considered regarding interface state recombination kinetics. Calculations are presented for the case of interface states being in equilibrium with the metal (Model (I), in equilibrium with the majority carriers of the semiconductor (Model II) and in equilibrium with the minority carriers (Model III). It is found that in all three cases, the efficiency of low barrier height, Schottky barrier cells can be increased very significantly. For example, it is shown that for a band gap of 1.5 eV and a barrier height of 0.5 eV, it appears possible to increase the cell efficiency from essentially zero to 12%. If the barrier height is 1.0 eV, an efficiency of over 20% is possible. It is determined, however, that MIS solar cell performance is limited by leakage currents due to minority carrier diffusion back into the bulk. As a result, the upper limit of performance is defined by that for a homojunction. These calculations identify ranges of surface state density and interfacial barrier heights necessary for a good MIS solar cell.     

Radiation damage of thermally oxidized MOS capacitors

The influence of preparation parameters and the effect of X-rays (150 keV, 10⁴rad (Si)) on oxide charge Qoxand interface state density Nssin thermally oxidized MOS varactors under different biasing conditions during irradiation has been investigated. The interface state density was determined by the ac conductance method before and after irradiation. The oxide charge has been evaluated with regard to the charge Qssof the interface states. Qsshas beeu discussed with the aid of simple models concerning the energetic distribution and recharge character of the interface states. The results indicate a similar dependence between flatband voltage, interface state density, and normalized oxide charge density as a function of gate bias during irradiation. Furthermore, the so-called "oxidation triangle" of oxide charge before irradiation exists for interface states as well. Calculations on the basis of the Schottky barrier model of the irradiated MOS structure show that the radiation-induced charge exists at both interfaces in the oxide layer. Radiation tolerance of the MOS capacitors as a function of technological parameters is discussed.     

The current-voltage-temperature characteristics of Al/NPB/p-Si contact

The current-voltage (I-V) characteristics of the Al/NPB/p-Si contact shows rectifying behavior with a potential barrier formed at the contact interface. The barrier height and ideality factor values of 0.65 eV and 1.33 are measured at the forward bias of the diode. The barrier height of the Al/NPB/p-Si diode at room temperature is larger that (∼0.58 eV) of conventional Al/p-Si diode. It reveals the NPB organic film control the carrier transport of the diode at the contact interface. The temperature effect on the I-V measurement is also performed to reveal the junction characteristics. The ideality factor of the Al/NPB/p-Si contact increases with decreasing temperature. And the barrier height decreases with decreasing temperature. The effects are due to the existence of the interface states and the inhomogeneous of the barrier at the junction.     

Schottky barrier parameters and structural properties of rapidly annealed Zr Schottky electrode on p-type GaN

The Schottky barrier junction parameters and structural properties of Zr/p-GaN Schottky diode are explored at various annealing temperatures. Experimental analysis showed that the barrier height (BH) of the Zr/pGaN Schottky diode increases with annealing at 400℃ (0.92 eV (I-V)/1.09 eV (C-V)compared to the asdeposited one (0.83 eV (I-V)/0.93 eV (C-V). However, the BH decreases after annealing at 500℃. Also, at different annealing temperatures, the series resistance and BH are assessed by Cheung''s functions and their values compared. Further, the interface state density (N_SS)of the diode decreases after annealing at 400℃ and then somewhat rises upon annealing at 500℃. Analysis reveals that the maximum BH is obtained at 400℃, and thus the optimum annealing temperature is 400℃ for the diode. The XPS and XRD analysis revealed that the increase in BH may be attributed to the creation of Zr-N phases with increasing annealing up to 400℃. The BH reduces for the diode annealed at 500℃, which may be due to the formation of Ga-Zr phases at the junction. The AFM measurements reveal that the overall surface roughness of the Zr film is quite smooth during rapid annealing process.     

Potential barrier formation at a metal-semiconductor contact using selective removal of atoms

The possibility of forming a potential profile in a semiconductor by forming a metal film on its surface via selective removal of oxygen atoms from a deposited metal oxide layer was studied. Selective removal of atoms (SRA) was performed using a beam of accelerated protons with an energy of about 1 keV. Epitaxially grown GaAs films with a thickness of ～100 nm and an electron concentration of 2×10¹⁷ cm^?3 were chosen as the semiconductor material, and W obtained from WO₃ was used as the metal. The potential profile appeared due to the formation of a Schottky barrier at the metal-semiconductor interface. It was found that the Schottky barrier formed at W/GaAs contacts made by the SRA method is noticeably higher (～1 eV) than the barrier formed at the contacts made by conventional metal deposition (0.8 eV for W/GaAs). The data presented indicate that there is no damaged layer in the gate region of the structures, which is most strongly affected by the proton irradiation. Specifically, it was shown that the electron mobility in this region equals the mobility in bulk GaAs with the same doping level.     

Thermally stimulated current measurements on a UV irradiated organic photoreceptor layer

Thermally stimulated current (TSC) measurements have been performed on a xerographic photoreceptor which has been treated with ultraviolet (UV) radiation. The charge transport layer of the photoreceptor consists of a polyester molecularly doped with an arylamine substituted hydrazone which was observed to undergo UV induced rearrangement to an indazole derivative. The indazole derivative is transparent to the wavelength component inducing the photo-reaction so that the depth of converted material gradually extends farther into the CTL with UV exposure time. The xerographic residual potential variation with irradiation time is attributed to the formation of a potential barrier to transfer of charge from hydrazone hopping states to indazole hopping states. The mobility activation energy obtained from TSC measurements is 0.22 eV for unirradiated material, which decreases to 0.12 eV after 1200 s of irradiation. The latter energy is identified as a signature of the potential barrier. This identification is corroborated by the correlation between the decrease of the residual potential and the increase of the TSC activation energy after 3600 s of irradiation.     

低真空退火对GaN MSM紫外探测器伏安特性的影响

利用金属有机化学气相沉积生长的非故意掺杂GaN单晶制备了金属一半导体一金属交叉指型肖特基紫外探测器。用肖特基势垒的热电子发射理论研究了低真空下不同热退火条件对器件伏安特性的影响。Au-GaN肖特基势垒由退火前的0．36eV升高到400℃0．5h的0．57eV,退火延长为1h势垒反而开始下降。分析结果表明：由工艺造成的填隙Au原子引入的缺陷是器件势垒偏低的主要原因,Au填充N空位形成了施主型杂质是退火后势垒升高的主要原因。     

HgCdTe—CdTe异质结构的变频导纳特性

采用宽频带导纳测试系统研究了Ｈｇ０．６６Ｃｄ０．３４Ｔｅ－ＣｄＴｅ异质结构和Ａｌ－半绝缘ＣｄＴｅ－Ｈｇ０．６６Ｃｄ０．３４Ｔｅ结构样品的变频导纳特性，分析了不同结构样吕的测试结果，表明：异质结ＨｇＣｄＴｅ表面空穴积累，ＣｄＴｅ表面空穴耗尽，界面处的势垒使载流子局限于ＨｇＣｄＴｅ体内，样品的光伏响应光谱在２９７０ｃｍ＾－１和３６５０ｃｍ＾－１处各有一个响应峰，前者对应于界面ＨｇＣｄＴｅ的本征光伏效庆     

Aluminum—Silicon Schottky barriers and ohmic contacts in integrated circuits

Experimental observations (electrical characteristics and in depth Auger analysis) have been made of the interface behavior in aluminum-silicon contacts. The barrier heights of these contacts (φbnfor n-type, φbpfor p-type silicon) are sensitive to heat treatments (HT) that are a part of normal integrated circuit processing. If oxide layers (≃20 Å) are present in the Al-Si interface, φbncan be as low as 0.45 eV and φbpas high as 0.75 eV. One can obtain reproducible barrier heights φbp≃ 0.7 eV and φbp≃ 0.5 eV by HT at T ≤ 300deg;C. As the temperature of HT is increased (up to ≃ 550deg;C) φbncan reach ≃ 0.9 eV and φbpdrop to < 0.35 eV. The HT at higher temperatures are accompanied by changes in the Al and Si profiles across the interface region. Two mechanisms have been found to be responsible for the changes in barrier height: 1) the removal of positive charges from the oxide, and 2) metallurgical reactions between the Al and Si. These two mechanisms have been separated and their individual behaviors qualified.