Abstract

Mid-wave infrared (MWIR) light sources are of growing importance because of applications in infrared scene generation, infrared counter measures (IRCM), spectroscopic chemical and biological threat monitoring, medical diagnostics and gas sensors. MWIR light emitting diodes (LED) are desirable for many such applications because of considerable advantages in terms of low cost, small volume, long term reliability, broad spectral content, and fast switching speed. Inter-band cascade (IC) LEDs utilize optical transitions between the conduction and valence bands involving spatial tunneling in a staircase of type II quantum well (QW) structures. We have reported mid-infrared LED light emission in the 3-4.5 urn wavelength regions using IC LED structure¹. For LEDs operating from the UV to the near-IR region, different structures such as the truncated-inverted pyramid, epitaxial liftoff, and textured top surface have been used to increase the external extraction efficiency. Though most of the surface treatment studies deals with visible LEDs, very few experiments have been made to improve MWIR LED performance.

© 2007 IEEE