扩散pn结扩散p区中平均少子扩散长度的测定

本文分析了用表面光压(SPV)法测量扩散pn结扩散p区中平均少子扩散长度的可行性,给出了有效少子扩散长度L_0与结深x_i、扩散区及衬底少子扩散长度L_1、L_2的关系曲线;提供了一种确定扩散区少子扩散长度的方法。     

Si基HgCdTe变面积光伏探测器的变温特性研究

通过变面积Si基HgCdTe器件变温I-V测试和暗电流特性拟合分析,研究了不同偏压下n-on-p型Si基HgCdTe光伏器件的暗电流成分与Si基HgCdTe材料少子扩散长度和少子寿命随温度的变化规律.在液氮温度下,随着反向偏压的增大器件的表面漏电流在暗电流中所占比重逐渐增加.在零偏压下,当温度低于200 K时材料的少子...     

用CCWT方法确定少子的体产生寿命及表面产生速度

在MOS由非平衡深耗尽态恢复到平衡反型态的过程中,如果MOS系统的总电荷是恒定的,则空间电荷区宽度的瞬态特性W(t)将提供少子的体产生寿命τ及表面产生速度S的信息;用指数衰减函数比较法可以直接由W-t曲线确定τ、S,省去了Zerbst方法的繁琐作图程序.     

CdSe@CdTe核壳II型量子点掺杂的薄膜太阳能电池

采用胶体化学法制备了CdSe@CdTe核壳量子点,将其置于CdTe量子点层与CdSe量子点层间构筑了三层结构的全无机薄膜太阳能电池(ITO/CdTe/CdSe@CdTe/CdSe/Al),在电池制备过程中对量子点薄膜进行了退火处理。吸收光谱、荧光光谱及荧光寿命测试结果表明所制备的CdSe@CdTe量子点为典型的II型量子点。其光电转换性能测量结果表明所制太阳能电池具有高达0.48%的能量转换效率,这主要得益于三层量子点间能带能量的差异对电子与空穴的定向传输的促进以及退火工艺对薄膜结晶质量的改善。     

直拉硅单晶热处理及其对太阳电池性能的影响

研究了直拉头尾料P型硅单晶片在360～1 300℃范围热处理前后氧碳含量、电阻率和少子扩散长度的变化规律及其对所制成太阳电池性能的影响。已证实在最佳的热处理条件下样品含氧量减少,少子扩散长度和电池效率达到最大,比未作热处理的单晶电池效率提高0.5～2倍,为利用这类单晶提供了有效方法。对此现象用热施主与深中心相互作用的模型作了初步解释。     

Ge/Si量子阱结构的C-V特性的模拟

采用有限深对称方势阱近似模型求解薛定谔方程得到Ge/Si量子阱中的子能级分布,并基于迭代法数值求解泊松方程模拟计算了量子阱结构样品在不同偏压下的载流子浓度分布和C-V特性.C-V曲线上电容平台的存在是量子阱结构C-V特性的显著特征,它与量子阱结构参数有密切的关系.随着覆盖层厚度的减小,C-V曲线上平台起始点的电容值增加,并且向低电压方向移动直至其消失.随着量子阱中的掺杂浓度提高,阱中的载流子浓度也会相应增加,那就需要更高的外加电压才能耗尽阱中的载流子,因此平台宽度也就随着掺杂浓度的增加而增加.当覆盖层厚度增加时,由于电压的分压作用,使得降在量子阱上的分压相应减少,因此需要更大的外加偏压才能使阱中载流子浓度全部耗尽,这就使平台的宽度增大.同样地,当覆盖层掺杂浓度增加时,覆盖层中更多的载流子转移到阱内,也就需要更高的外加偏压才能使阱中载流子全部耗尽,平台的宽度也就随之增大.     

Ge/Si量子阱结构的C-V特性的模拟

采用有限深对称方势阱近似模型求解薛定谔方程得到Ge/Si量子阱中的子能级分布,并基于迭代法数值求解泊松方程模拟计算了量子阱结构样品在不同偏压下的载流子浓度分布和C-V特性.C-V曲线上电容平台的存在是量子阱结构C-V特性的显著特征,它与量子阱结构参数有密切的关系.随着覆盖层厚度的减小,C-V曲线上平台起始点的电容值增加,并且向低电压方向移动直至其消失.随着量子阱中的掺杂浓度提高,阱中的载流子浓度也会相应增加,那就需要更高的外加电压才能耗尽阱中的载流子,因此平台宽度也就随着掺杂浓度的增加而增加.当覆盖层厚度增加时,由于电压的分压作用,使得降在量子阱上的分压相应减少,因此需要更大的外加偏压才能使阱中载流子浓度全部耗尽,这就使平台的宽度增大.同样地,当覆盖层掺杂浓度增加时,覆盖层中更多的载流子转移到阱内,也就需要更高的外加偏压才能使阱中载流子全部耗尽,平台的宽度也就随之增大.     

双势垒量子阱薄膜力电耦合特性实验

用分子束外延方法在(001)GaAs衬底上生长了AlAs/InGaAs双势垒量子阱薄膜结构.介绍了量子阱薄膜在(110)与(110)方向单轴压应力作用下的力电耦合实验,测试出量子阱薄膜在室温下随着外加压力变化的I-V曲线.测试结果表明:量子阱薄膜I-V曲线的共振峰在(110)方向单轴应力作用下向正偏压方向漂移,在(110)方向应力作用下向负偏压方向偏移,并分析了量子阱薄膜力电耦合效应的物理成因.该结果与基于量子阱力电耦合特性的介观压阻理论的研究结果相吻合.     

双势垒量子阱薄膜力电耦合特性实验

用分子束外延方法在(001)GaAs衬底上生长了AlAs/InGaAs双势垒量子阱薄膜结构.介绍了量子阱薄膜在(110)与(110)方向单轴压应力作用下的力电耦合实验,测试出量子阱薄膜在室温下随着外加压力变化的I-V曲线.测试结果表明:量子阱薄膜I-V曲线的共振峰在(110)方向单轴应力作用下向正偏压方向漂移,在(110)方向应力作用下向负偏压方向偏移,并分析了量子阱薄膜力电耦合效应的物理成因.该结果与基于量子阱力电耦合特性的介观压阻理论的研究结果相吻合.     

内偏压隔离

本文对一种新的隔离方法进行了理论分析与计算.通过分析和计算的结果,我们给这种隔离方法定名为内偏压隔离,从而反映了这种隔离方法的物理实质.内偏压隔离,主要是利用p型和n型半导体相接触时所形成的接触电势差V_B(也称为扩散电势或内部偏压)的作用.V_B这个偏压是由载流子的扩散运动形成的.这个偏压的数值取决于杂质浓度和本征载流子浓度.在高补偿的晶体中,由于内偏压的作用,将展开一个较宽的耗尽区.当集成电路中外延层厚度相对薄时,这个耗尽区宽度可大于外延层厚度,从而切断外延层,以达到隔离外延层把外延层分成多个隔离岛的目的.这个隔离方法不需要单独的隔离区和单独的隔离扩散.只要适当的控制电路制作过程中的掺金量,使之形成较强的补偿,即可实现隔离.因此,这种隔离方法不但减少工艺程序、节省成本、减少设备,而且可以大大提高电路的集成度,提高电路的成品率.所以对中、大规模电路的研制和生产是有益的.采用这种工艺,可使TTL型的中、大规模电路在集成度方面与MOS电路,I~2L电路比美,而在速度方面却遥遥领先.     

Optical MTF and quantum efficiency analysis in a finite slab

The formula for quantum efficiency in a semiconducting material was first derived by Seib in 1974 for a semi-infinite slab of semiconducting material. Seib's first-order analysis considered the effect of absorption coefficient, minority carrier diffusion length and depletion width. However, for modern devices on epitaxial material, smart sensors, quantum well devices, etc., the semi-infinite slab approximation breaks down. Here, we present the derivation for a finite slab that considers the thickness of the layer as a fourth parameter. We present a case study analyzing quantum efficiency, and hence MTF, in epitaxial silicon versus bulk gallium arsenide.     

Numerical evaluation of the scanning method for the determination of minority carrier diffusion length in p-n junctions

A numerical model for the scanning method for determining minority carrier diffusion length is presented to include the effect of the built-in field and high-level injection. A numerical simulation is presented which shows that the scanning method for diffusion length measurements will not give accurate results for minority carrier diffusion length in the region where the presence of a built-in field is significant. No matter how poor the junction is made, the accuracy of the measurement method increases away from the depletion region. The problem of low magnitude in the induced short circuit current away from the physical junction could be overcome by increasing the generation level. For substrate dopant concentrations between 2.0 × 10¹⁵cm⁻³ and 6.0 × 10¹⁶cm⁻³ the distance into the device from the surface where the error of the measurement will be greater than 10% is expressed as a semi-empirical formula relating dopant concentration. When there are irregularities in minority carrier lifetime closer to the physical junction, the measurement method will accurately determine the minority carrier diffusion length in a particular region only if the width of that region is much larger than its diffusion length.     

全无机胶体量子点太阳能电池中少数载流子寿命测量

准确测量太阳能电池材料少数载流子寿命在电池研究生产中至关重要.利用开路电压衰减(OCVD)技术以ns光脉冲(光脉冲宽度8 ns、频率为10 Hz)作为激发光源,获到了全无机胶体量子点太阳能电池在不同温度(97 K～317 K)条件下的开路电压瞬态响应曲线.电池在低温(97 K～277 K)及高温(277 K～317 K...     

Effective lifetimes in high quality silicon devices

A correct interpretation of pn junction current-voltage and pulsed MOS capacitance-time data allows space-charge region width dependent generation parameters to be separated from bulk controlled recombination parameters. This is very important for the correct extraction of generation lifetime and minority carrier diffusion length, especially for intrinsically gettered devices where the recombination center density varies through the device. Methods to do this are discussed in this paper.     

The effect of the minority carrier distribution on the threshold voltage of a MOSFET

Based upon the concept of minority carrier transverse diffusion within the surface space charge region and its resultant quasi-Fermi level distribution, a simple one-dimensional theory of the threshold voltage for both long- and short-channel MOSFETs is developed. In the new model, the non-uniform distribution of the quasi-Fermi level for minority carriers with respect to that for majority carriers is characterized by introducing an effective diffusion length and is averaged over all the channel length. The non-uniformity in the quasi-Fermi level for minority carriers results in a non-uniform bulk charge density which is averaged similarly. Using the above averaged values and considering the charge-sharing effect, the threshold voltage for a MOSFET is expressed. Numerical results are obtained which show the strong dependence of threshold voltage on the effective diffusion length, which can not be overlooked especially when the device is scaled down. The theoretical calculations are also compared to the experimental data for the fabricated NMOS and PMOS. The good agreement supports the correctness of the developed theory.     

Analysis of drain breakdown voltage in SOI n-channel MOSFETs

The reduction of drain breakdown voltage in SOI nMOSFETs with floating substrate is related to the presence of a parasitic n-p-n bipolar structure, the base of which is the floating body of the device. reduction of breakdown voltage (compared to the case where a body contact is used) is shown to be dependent on both channel length and minority carrier lifetime in the SOI material. Conversely, it is shown that mere measurement of MOSFET breakdown voltages can be used to extract the minority carrier lifetime in the SOI material.<>     

Measurement of minority carrier lifetime in solar cells from photo-induced open-circuit voltage decay

We present an experimental technique for determining the excess minority carrier lifetime within the base region of p-n junction solar cells. The procedure is to forward-bias the solar cell with a flash from a stroboscope and then to monitor the decay of the open-circuit voltage. Results are given for conventional horizontal-junction devices, as well as for vertical single- and multijunction solar cells. Lifetimes obtained with this technique are compared with those obtained from a method based on open-circuit voltage decay following the abrupt termination of a forward current, and with results obtained from a traveling light spot measurement of base minority carrier diffusion length in vertical-junction solar cells, from which the lifetime can be inferred. It is found that the forward current method does not yield a reliable lifetime estimate.     

EBIC characterization of light-emitting structures based on GaN

EBIC investigations of light-emitting structures based on InGaN/GaN MQW with different numbers of wells have been carried out. A pronounced dependence of collection efficiency on quantum-well number is observed. A comparison with apparent carrier profiles calculated from C-V curves reveals a correlation between the collection efficiency and location of quantum well inside the depletion region. Defects producing bright EBIC contrast are revealed in the structure with five quantum wells. This contrast is associated with defects locally decreasing the excess carrier recombination inside quantum wells. The text was submitted by the authors in English.     

Determination of material parameters from regions close to the collector using electron beam-induced current

The conventional method of extracting the minority carrier diffusion length using the electron beam-induced current (EBIC) technique requires that the electron beam be placed at region more than two diffusion lengths away from the collector. The EBIC signals obtained under this condition usually has low signal to noise ratio. In addition, the true diffusion length of the sample is initially unknown and hence it is difficult to estimate how close the beam can be placed from the collector. To overcome all these difficulties, a new method of extracting minority carrier diffusion length from the EBIC signal is proposed. It is shown that this method can be applied to EBIC signals obtained from regions close to the collector. It is also shown that the surface recombination velocity of the sample can also be obtained using this method. This theory is verified using EBIC data generated from a device simulation software.