Optimization of pixelated GaAs/AlGaAs x-ray downconversion devices

The concept of semiconductor frequency conversion offers an alternative imaging approach, which eliminates the need for connecting a readout circuit. In this work, we present an improved architecture for the pixelated GaAs/AlGaAs x-ray downconversion device. Experimental results demonstrate that reducing the thickness of the semi-insulating GaAs (SI-GaAs) substrate can effectively enhance the photocurrent response. Additionally, indium tin oxide is employed as a transparent parallel electrode in place of the opaque metal ring electrode; this substitution not only simplifies the device fabrication but also increases the effective emission area. The lateral current spreading width in SI-GaAs is also quantified, offering practical guidelines for determining the minimum pixel dimensions and spacing. These structural optimizations provide a promising pathway toward the development of high-resolution pixelated x-ray down-converters.