Use of epitaxial unipolar barriers to block surface leakage currents in photodetectors



Surface leakage currents are one of the many causes of dark current exhibited by semiconductor devices and are a common limiting factor to device performance for many types of devices. Traditionally, these surface leakage currents are controlled through the post-epitaxial insertion of a surface passivation layer, but surface passivation is often expensive, time consuming, and not entirely effective. Unipolar barriers may be incorporated into electronic devices as a less expensive and more effective alternative way to control surface leakage currents. Unipolar barrier devices are demonstrated here using MBE-grown InAs nBn detectors and unipolar barrier photodiodes. A commercial InAs photodiode becomes surface leakage current limited at 220 K while the nBn detector shows no surface leakage current down to at least 135 K. The unipolar barrier photodiode shows no detectable surface leakage down to at least 130 K while a matching conventional photodiode is limited by surface conduction at a temperature of 150 K. This indicates the greatly improved performance of the unipolar barrier devices (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)