A. A. Telegin

Photovoltaic X-ray detectors on the basis of GaAs epitaxial structures

The results of investigations of the properties of a new photovoltaic X-ray detector are presented. The detector was manufactured on the basis of a GaAs (p+-n-n′-n+) epitaxial structure, which was grown using the vapor-phase epitaxy method. The detector sensitivity to X-rays in a range of effective energies of 7–120 keV was measured. Multichannel linear X-ray detectors were developed and used in obtaining high-quality digital images.

Photovoltaic GaAs Detectors for Digital X-Ray Imaging

The short coming of the conventional film-screen systems arises from limited dynamic range due to the film latitude and Swank noise from the screen and film granularity that limits the system rather than quantum fluctuations. A thin intensifying screen is used to achieve better spatial resolution; however thin screens also have limited detector quantum efficiency. Most currently available digital X-ray systems use scanned-slit geometries to minimize tehe required detector area and minimize system complexity. Scanned-slit systems achieve also efficient rejection of Compton scattered X-rays by suffering significant X-ray tube loading in comparison to conventional large-field imaging geometries. There remains a significant clinical need in production of detection systems with sufficiently high spatial resolution and detection quantum efficiency. An improvement of digital radiography compared to conventional systems is the high dynamic range. Futhermore real-time data acquisition is possible and digital image processing can be performed. A digital image representation has become feasible because of the availability of digital mass storage media.

Characteristics of a photovoltaic X-ray detector based on a GaAs epitaxial structure

The characteristics of a photovoltaic X-ray detector based on the GaAs p+-n-n′-n+ epitaxial structure grown using gas-phase epitaxy are studied. Typical current-voltage and capacitance-voltage characteristics of the epitaxial structures are analyzed together with the built-in electric field profile in the n-GaAs depleted region. The efficiency of charge accumulation in the photovoltaic detector is measured for zero bias and for a bias voltage of 17 V. It is shown that the GaAs-based photovoltaic X-ray detector can operate with zero bias voltage at room temperature. The sensitivity of the detector is measured as a function of the effective energy of X-rays and the angle of incidence of X-ray photons.

Multiple-pixel X-ray linear detector based on single CdZnTe crystals

The design of an X-ray linear detector based on single crystals Cd0.9Zn0.1Te has been described. The results of usage have been given.