SBIR-STTR Award

We propose the development of an instrument system to directly measure the minority carrier lifetime in strained layer superlattices. The Phase I instrument will demonstrate the measurement of lifetimes in the range of 10 ns to 1 us. Phase II development will extend this range to 10 ns to 35 us. The proposed instrument will use a combination of time resolved photoluminescence and optical modulation response to achieve its wide dynamic range.

Keywords:
Optical Modulation Response, Superlattice, Infrared Detector, Carrier Lifetime, Time Resolved Photoluminescence

We propose the development of a system for measuring the minority carrier lifetime in strained layer superlattices (SLS). Mid wave infrared (MWIR) and long wave infrared (LWIR) detectors based on SLS technology show promise due to the large and inexpensive focal plane arrays that can be fabricated. The devices are held back though, by excessive dark current, which is related to a poor minority carrier lifetime. This poor lifetime limits SLS detector performance relative to the currently utilized HgCdTe devices. The proposed system will allow for quick, repeatable, and accurate measurement of minority carrier lifetimes so that SLS researchers can make progress in developing these promising devices. The system is based on the optical modulation response technique, but is also capable of time resolved photoluminescence measurements. Excess carriers are produced by fiber coupled semiconductor laser, and excess carrier concentrations as low as 3*10^13 per cm cubed have been obtained.