Study of micro-germanium pixel detector under a moderate cryogenic condition

锗探测器广泛用于探测高能X射线光子，这是因为高能量分辨率和高探测效率。然而，在实践中，由于低特征能量（0.67eV），锗探测器必须在液氮温度下操作是不利的。锗探测器的暗电流由体电流和表面漏电流组成。另一方面，电离粒子产生的电子-空穴对的密度数与探测体积无关，随着电离粒子能量的增加而增加，并局限于几百μm以内。在电极像本工作中假设的像素尺寸一样小的情况下，（100 μm×100 μm），此外，噪声电流应降低到每像素100 nA以下，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至10 μA在这项研究中，我们研究了一个像素为60×97像素的尺寸为172 μm×172 μm的锗传感器。2005年10月23- 29日，在美国波多黎各举行的IEEE核科学与医学成像会议上，以“锗探测器的像素化效应及其温度依赖性”为题进行了讨论。

Germanium detectors are widely in use for detecting high energy X-ray photons, both because of the high energy resolution and because of high detection efficiency. However, it is a disadvantage in practice that Germanium detectors have to be operated at liquid nitrogen temperature due to the low characteristic energy (0.67 eV). It is well known that the dark current drawing in a given Germanium detector consists of the bulk current and the surface leakage one. 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. 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 per pixel, since it is proportional to the volume of the semiconductor each pixel electrode covers.We have confirmed that the noise current is already reduced to 10 μA at room temperature in a tiny germanium detector with a volume of 1 mm×1 mm×1 mm. In this study, we have investigated a pixilated Germanium sensor with 60×97 pixels of size 172 μm×172 μm. The result was talked as the title "Pixilation Effect on Germanium Detectors and Their Temperature Dependencies" in the IEEE conference : the Nuclear Science & Symposium & Medical Imaging Conference, Puerto Rico, October 23-29,2005.