MBE-GROWN HGCDTE MULTILAYER HETEROJUNCTION STRUCTURES FOR HIGH-SPEED LOW-NOISE 1.3-1.6-MU-M AVALANCHE PHOTODETECTORS

HgCdTe is an attractive material for room-temperature avalanche photod etectors (APDs) operated at 1.3-1.6 mu m wavelengths for fiber optical communication applications because of its bandgap tunability and the resonant enhancement of hole impact ionization for CdTe fractions near 0.73. The HgCdTe based separate absorption and multiplication avalanc he photodetector is designed and fabricated for backside illumination through a CdZnTe substrate. The multi-layer device structure is compri sed of seven layers including 1). n(+) contact 2). n(-) diffusion buff er 3). n(-) absorber 4). n charge sheet 5). n(-) avalanche gain 6). p to form junction, and 7), p(+) contact, Several wafers were processed into 45 mu m x 45 pm and 100 mu m x 100 mu m devices. The mean value o f avalanche voltage is 63.7 V measured at room temperature, At 1 GHz, the device shows a gain of about 7 for a gain-bandwidth product of 7 G Hz. This first demonstration of an all molecular beam epitaxially grow n HgCdTe multi-layer heterojunction structure on CdZnTe substrates rep resents a significant advance toward the goal of producing reliable ro om temperature HgCdTe high speed, low noise avalanche photodetectors.