Disclosed herein is an apparatus and a method of making the apparatus. The method comprises obtaining a plurality of semiconductor single crystal chunks. Each of the plurality of semiconductor single crystal chunks may have a first surface and a second surface. The second surface may be opposite to the first surface. The method may further comprise bonding the plurality of semiconductor single crystal chunks by respective first surfaces to a first semiconductor wafer. The plurality of semiconductor single crystal chunks forming a radiation absorption layer. The method may further comprise forming a plurality of electrodes on respective second surfaces of each of the plurality of semiconductor single crystal chunks, depositing pillars on each of the plurality of semiconductor single crystal chunks and bonding the plurality of semiconductor single crystal chunks to a second semiconductor wafer by the pillars.