GaAs arrays for x-ray spectroscopy

We present results from our compound semiconductor laboratory program and describe the development of a large area GaAs imaging array for planetary remote sensing applications. The device is fabricated from ~150 micron thick epitaxial material, patterned into a 64 x 64 pixel array, back-thinned and contacted. It will be flip-chip bump bonded onto a custom designed, fully spectroscopic, low noise (< 20 e- rms) active pixel sensor ASIC. At present, the ASIC is still under development and so in order to validate and qualify the various technological steps, we have produced a GaAs imager based on the MEDIPIX-1 format using a MEDIPIX-1 readout chip. In X-ray tests, the device was found to work well with a bump yield of 99.9%. After flat field corrections, the spatial uniformity of the array was commensurate with Poisson noise.