神马品牌网空气净化器哪个品牌好?:请高手翻译3段 奖15积分
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(1)the actual respose of the detector depends whether the contacts tothe semiconductor are ohmic or blocking(for example Schottky that do not inject carriers )and on the nature of carrier recobination kinetics.we will consider a photoconductor with ohmic contacts(that is,the contacts is do not limit the current flow as in the case of a Schottky junction contact).with ohmic contacts,the photocondictor exhibits photoconductive gain,that is the external photocurrent is due to more than one eletron flow per absorbed photon as illustrated in Figure5.18 as explained below
(2)
the pin photodiode structure shown in Figure5.6is,of course,idealized.in reality,the i-Si layer will have some small doping.for example,if the sandwiched layer is lightly n-type doped it is labeled as a v-layer and the structure is p+vn+.the sandwiched v-layer becomes a depletion layer with small cocentratron of exposed positive donors.the field then is no entirely uniform across the photodiode.the field is maximum at the p+v junction and decreases slightly across v-Si to reach the n+side.as an approximation we can still the v-Si layer
(3)
the choice of material for a photodiode must be such as that the photon energies are greater than Eg.futher,at the wavelength of radiation,the absorption occurs over a depth covering the depletion layer so that the photogenerated EHPs can be separated by the field and collected at the electrons.if the absorption coefficient is too largr then absorption will occur very near the surfaceof the p+ layer which is outside the depletion layer.first,the absence of a field means that the photogenerated electron can only make it to the depletion layer to cross tothe n-sideby diffusion.secondly,photogeneration near the surface invariably leads to rapid recombination due to surface defects that act as recombination centers.on the other hand,if the absorption coefficient is too small,only a small portion of photons will be absorbed in the depletion layer and only a limited numbri of EHPs can be photogenerated
(2)
the pin photodiode structure shown in Figure5.6is,of course,idealized.in reality,the i-Si layer will have some small doping.for example,if the sandwiched layer is lightly n-type doped it is labeled as a v-layer and the structure is p+vn+.the sandwiched v-layer becomes a depletion layer with small cocentratron of exposed positive donors.the field then is no entirely uniform across the photodiode.the field is maximum at the p+v junction and decreases slightly across v-Si to reach the n+side.as an approximation we can still the v-Si layer
(3)
the choice of material for a photodiode must be such as that the photon energies are greater than Eg.futher,at the wavelength of radiation,the absorption occurs over a depth covering the depletion layer so that the photogenerated EHPs can be separated by the field and collected at the electrons.if the absorption coefficient is too largr then absorption will occur very near the surfaceof the p+ layer which is outside the depletion layer.first,the absence of a field means that the photogenerated electron can only make it to the depletion layer to cross tothe n-sideby diffusion.secondly,photogeneration near the surface invariably leads to rapid recombination due to surface defects that act as recombination centers.on the other hand,if the absorption coefficient is too small,only a small portion of photons will be absorbed in the depletion layer and only a limited numbri of EHPs can be photogenerated
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pin photodiode ：PIN光电二极管（应该是大写的PIN）
肖特基（Schottky）
field:电磁学名词：场
其他术语不再列举，因为李某每次答题属于走在前面的做法很受非议。
(1)检测器的实际反应取决于半导体的接触是电阻接触型或阻挡接触型(例如不注射载体的肖特基)和载体的重组动力学本质。我们认为一个带有接触电阻的光电导体(也就是说，接触并不限制电流流动，例如肖特基连接接触的情形)。带有电阻接触的光电管呈现光敏特性，那就是由于每个吸收光子流过的多于一个电子造成的外层光电流，图5.18所示并解释如下：
(2)
PIN光电二极管结构如图5.6所示，当然，仅是理想化的。事实上，i-Si层有一些微型杂质。例如, 如果夹心层是少量的N型掺杂就标记为V-层并且结构是P+VN+。夹心v-层变成一个带有低浓度阴性材料的耗尽层。那么光电二极管横截面场就不是完全均匀的。P+V结场最大，V-Si层截面到N+一边轻微下降。作为一个近似值我们还要考虑V-Si 层
(3)
光电二极管的选材必须保证光子能量大于Eg。进一步说，辐射波长在耗尽层相当深度处发生吸收以便于生光EHPs可以被场分离并收集电子。如果吸收系数太大那么吸收将在P+层表面附近也就是外耗尽层发生。首先，场的缺失意味着生光电子只能靠散射由耗尽层跨过N边。其次，表面附近的生光作用总是引起快速重组，由于表面缺陷可作为重组中心。另一方面，如果吸收系数太小，只有很少一部分光子被耗尽层吸收，仅有有限量的EHPs 能产生光。
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