Experimental studies on the temperature dependence of Germanium semiconductor detectors and on their pixilation for high spatial resolutions

锗半导体探测器的温度依赖性及其高空间分辨率像素化的实验研究

• 批准号: 14390062
• 负责人: TOYOKAWA Hidenori
• 金额: $ 3.9万
• 依托单位: Japan Synchrotron Radiation Research Institute
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14390062/
• 关键词: lonization radiation detector; Semiconductor detector; Germanium detector; Pixel detector

The noises current originated by thermal generation of electron-hole pairs in semiconductor detectors is basically governed by the Boltzmann factor of exp(-E_<th>/kT), where E_<th> denotes the characteristic energy, k Boltmann constant, and T the absolute temperature. Silicon semiconductor detectors can be operated at room temperature, because the number of density of electron-hole pairs, n_<e-h>, in silicon is on he order of 10^<10> cm^<-3> at T=25℃ owing to the high value of E_<th>(1.1 eV). On the contrary, n<e-h> in germanium is as high as 10^<13> cm^<-3> at T=25℃ due to the low value of E_<th>(0.7 eV), making the cryogenic condition compulsory to the operation of germanium semiconductor detectors. However, n_<e-h> in germanium at moderate cryogenic condition (T=-65℃) is already as low as that in silicon at room temperature. With an electrode as small as the pixel size assumed in the present work (100 μm × 100 μm), furthermore, the noise current should be reduced less than 100 nA pe … More r pixel, since it is proportional to the volume of the semiconductor each pixel electrode covers. The number of density of electron-hole pairs generated by ionizing particles is, on the other hand, independent from the detection volume, increases with the energy of ionization particles, and localized within a few hundreds μm. This argument suggests that, when pixilated in a few hundreds μm, the germanium semiconductor can be operated near room temperature. The present study has confirmed that the noise current is already reduced to 10 mA at room temperature in a tiny germanium detector with a volume of 1 mm × 1mm, and is further reduced by two orders of magnitude at T=-73℃. This implies that the noise current will be reduced below 30 nA with a germanium crystal pixilated into a proposed standard size of 0.2 mm × 0.2 mm × 0.3 mm, and supports the operation possibility of a pixilated germanium detector at near room temperature. However, there was a dark current observed with an applied voltage higher than 10 V, which is presumably a surface leakage current. The latest version of pixilated germanium detectors fabricated has, therefore, a crystal volume of 5 mm × 5 mm, a pixel size of 0.75 mm × 0.75 mm, and a pixel number 2 × 2, together with a guard-ring electrode that is to remove the dark current. Less

半导体探测器中电子-空穴对热产生的噪声电流基本上由exp的Boltzmann因子(-E^th/kt)决定，其中E<th>表示特征能量，k Boltmann常数，T表示绝对温度。硅半导体探测器可以在室温下工作，因为在T=25℃时，由于E<th>(1.1 eV)的高值，硅中电子-空穴对的密度约为10^lt；10 eV；-3。相反，在T=25℃时，由于E<th>(0.7 eV)的低值，Ge中的n&lt；e-h&gt；高达10^&lt；13&gt；cm^&lt；-3&gt；，这使得Ge半导体探测器必须在低温条件下工作。然而，在中等低温条件下(T=-65℃)，锗中的n_&lt；e-h&gt；已经和室温下硅中的n_t；e-h&gt；一样低。使用与本工作中假设的像素尺寸(100μm×100μm)一样小的电极，此外，噪声电流应降低到100nape…以下更多r个像素，因为它与每个像素电极覆盖的半导体的体积成比例。另一方面，电离粒子产生的电子-空穴对的密度与探测体积无关，随着电离粒子能量的增加而增加，并且局域化在几百μm以内。这表明，当象素化在几百μm时，Ge半导体可以在室温附近工作。本研究证实，在体积为1 mm×1 mm的微型锗探测器中，噪声电流在室温下已降低到10 mA，在T=-73℃时又降低了两个数量级。这意味着，将锗晶体像素化成0.2 mm×0.2 mm×0.3 mm的标准尺寸，噪声电流将降低到30nA以下，并支持像素化锗探测器在近室温下工作的可能性。然而，在高于10V的施加电压下观察到了暗电流，这可能是表面泄漏电流。因此，最新研制的像素化锗探测器的晶体体积为5 mm×5 mm，像素尺寸为0.75 mm×0.75 mm，像素数为2×2，并配有去除暗电流的保护环电极。较少

项目成果

M.Suzuki: "Multielement Detectors for High Energy SR X-ray Experiments"AIP Conference Proceedings. (to be published).

M.Suzuki：“用于高能 SR X 射线实验的多元素探测器”AIP 会议记录。

A.Gorin: "fundamental properties of YAP Imager"Nucl.Instr.and Meth.. A510. 76-82 (2003)

A.Gorin：“YAP 成像仪的基本特性”Nucl.Instr.and Meth..A510。

E.F.Eikenberry: "PILATUS : a two-dimensional X-ray detector for macromolecular crystallography"Nuclear Instruments and Methods in Physics Research A. A501. 260-266 (2003)

E.F.Eikenberry：“皮拉图斯：用于大分子晶体学的二维 X 射线探测器”物理研究中的核仪器和方法 A. A501。

鈴木昌世: "放射光科学に於けるX線検出器の現状と将来"放射線. Vol.29, No.1. 3-8 (2003)

Masayo Suzuki：“同步辐射科学中 X 射线探测器的现状和未来”辐射，第 29 卷，第 1 期。

K.Hirota: "A fast position encoding system for a high energy X-ray YAP imager"Nucl.Instr.and Meth.. A513. 187-192 (2003)

K.Hirota：“用于高能 X 射线 YAP 成像仪的快速位置编码系统”Nucl.Instr.and Meth..A513。