Abstract InAs/GaAs quantum dot photodetector photoresponse spectra consist of quantum dot, wetting layer and GaAs components, however, they frequently contain features attributed to defect levels. In this study we focus on the origin of an unwanted negative photovoltage component in order to find a design allowing to eliminate these undesirable effects. Photoelectric properties of vertical InAs/GaAs quantum dot structures grown on semi-insulating (si) and n+-GaAs wafers are analyzed. It is found that the photoresponse drop above 1.37 eV in the photovoltage spectrum, observed with si-GaAs substrate, is originated from shallow defect levels in the unintentional space-charge area created at the interface between the substrate and n+-GaAs buffer. The intrinsic field in that area is opposite to the top pn junction, according to modelling calculations, and it reduces the photoelectric response. Photoelectric characterization of the heterostructure grown on n+-GaAs indicates that the utilization of n+-GaAs substrate helps to avoid this band bending and to eliminate its negative effects, increasing the total photoresponse.

中文翻译：

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InAs/GaAs 量子点光电探测器结构中负光电压分量的缺陷能级和界面空间电荷面积

摘要 InAs/GaAs 量子点光电探测器光响应光谱由量子点、润湿层和 GaAs 组成，然而，它们经常包含归因于缺陷水平的特征。在这项研究中，我们专注于不需要的负光电压分量的起源，以便找到一种可以消除这些不良影响的设计。分析了在半绝缘 (si) 和 n+-GaAs 晶片上生长的垂直 InAs/GaAs 量子点结构的光电特性。发现用 si-GaAs 衬底观察到的光电压谱中光响应下降超过 1.37 eV，源于在衬底和 n+-GaAs 缓冲液之间的界面处产生的无意空间电荷区域中的浅缺陷水平。根据建模计算，该区域的本征场与顶部 pn 结相反，并降低光电响应。在 n+-GaAs 上生长的异质结构的光电特性表明，使用 n+-GaAs 衬底有助于避免这种带弯曲并消除其负面影响，从而增加总光响应。