A germanium hybrid pixel detector with 55μm pixel size and 65,000 channels

Abstract

Hybrid pixel semiconductor detectors provide high performance through a combination of direct detection, a relatively small pixel size, fast readout and sophisticated signal processing circuitry in each pixel. For X-ray detection above 20 keV, high-Z sensor layers rather than silicon are needed to achieve high quantum efficiency, but many high-Z materials such as GaAs and CdTe often suffer from poor material properties or nonuniformities. Germanium is available in large wafers of extremely high quality, making it an appealing option for high-performance hybrid pixel X-ray detectors, but suitable technologies for finely pixelating and bump-bonding germanium have not previously been available.A finely-pixelated germanium photodiode sensor with a 256 by 256 array of 55 µm pixels has been produced. The sensor has an n-on-p structure, with 700 µm thickness. Using a low-temperature indium bump process, this sensor has been bonded to the Medipix3RX photoncounting readout chip. Tests with the LAMBDA readout system have shown that the detector works successfully, with a high bond yield and higher image uniformity than comparable high-Z systems. During cooling, the system is functional around -80 • C (with warmer temperatures resulting in excessive leakage current), with -100 • C sufficient for good performance.

Review of hybrid pixel detector readout ASICs for spectroscopic X-ray imaging

“…For the majority of X-ray imaging applications, where the incoming X-ray beam is between 20 keV and 120 keV, a high quantum efficiency is required, for which higher-Z materials are employed. Commonly used materials are Ge [20], GaAs [21], CdTe [22] and CdZnTe [23]. Another approach to increase the quantum efficiency of a system is to use silicon sensors in a geometry oriented edge-on to the beam ( [24,25]).…”

Photon Counting Detectors for X-Ray Imaging With Emphasis on CT

“…In Table II, apart from the traditional materials typically used as radiation detectors (Si [52], Ge [53], GaAs [54], [55], CdTe [30], and CdZnTe [56]) the authors have also included leaded halide perovskites, a material that is gaining some attention in the field of radiation detection [57], [58]. The reason is the strong stopping power [the material contains Pb (Z = 82)] and the fact that the crystal grows from a low cost solution.…”

Overview of GaAs und CdTe Pixel Detectors Using Medipix Electronics

“…These detectors showed an excellent performance and well-defined interconnection technology. The strong improvement of the quality of the CdTe material allowed the production of larger area, monolithic pixel detectors with more than 350.000 pixels for 55 m pixel pitch with Medipix2 (Koenig et al [27] ) and Medipix3 (Pennicard et al [28] ). A flatfield image of a CdTe 42 × 28 mm 2 detector module with Medipix3 is shown in Figure 8.…”