Fast pixelated quantum-well-based sensor for multi-wavelength photon detection

In order to cover a wide range of experimental applications, the opportunity to use InGaAs/InAlAs quantum well (QW) devices as fast pixelated photon detectors has been investigated. QW structures are planar objects in which electrons are confined in one dimension. Devices with several combinations of barrier and well materials can be fabricated by using compound semiconductors; in the case of InGaAs/InAlAs QWs this allows to tune the energy band gap down to 0.6 eV. Thanks to their direct, low-energy gap such devices operated at room temperature may be used as detectors for photon energies ranging from visible to hard X-ray. Internal charge amplification mechanism can be applied for very low signal levels, while the high carrier mobility allows the design of very fast photon detectors with sub-nanosecond response times. QW devices grown with molecular beam epitaxy have been pixelated by using standard photolithographic techniques. In order to fit commercially available readout chips, a pixelated sensor with pixel size of 172 x 172 mu m(2) is currently under development. A small-scale version of the pixelated QW sensor has been preliminarily tested with synchrotron radiation, conventional X-rays and UV laser light. The reported results indicate that these devices show fair charge sharing in the clearances between the pixels and feature very short response times to 100-fs-wide laser pulses.