Device challenges for biodetection

Abstract

Optical characterization of nitride semiconductors and device testing of ultraviolet emitters and detectors comprised of these materials are employed in addressing the challenges faced in developing semiconductor-based, compact, lowcost, low-power-consumption biodetection systems. Comparison of time-resolved photoluminescence (TRPL) on UV LED wafers prior to fabrication with subsequent device testing indicate that the best performance is attained from active regions that exhibit both reduced nonradiative recombination due to saturation of traps associated with point and extended defects and concomitant lowering of radiative lifetime with increasing carrier density. Temperature and intensity dependent TRPL measurements on a new material, AlGaN containing nanoscale compositional inhomogeneities (NCI), show that it inherently combines inhibition of nonradiative recombination with reduction of radiative lifetime, providing a potentially higher efficiency UV emitter active region. In addition, testing of GaN avalanche photodiodes (APDs) on low defect density bulk GaN substrates indicates that for the first time GaN APDs with diameters as large as 50 microns exhibit reproducible gain greater than 1000. These results show promise for replacement of photomultipliers in biodetection systems.