"High Resolution Mapping of Infrared Photoluminescence"

Robert Furstenberg¹, Jeffrey O. White¹ and John H. Dinan²

1. University of Illinois, Materials Research Laboratory, Urbana, IL

2. U.S. Army Night Vision and Electronic Sensors Directorate, Fort Belvoir, VA

ABSTRACT

Due to its non-destructive nature, high-resolution photoluminescence (PL) mapping can be a useful tool for quality assessment of wafers prior to device growth. Mapping in the visible region of the spectrum is now routinely performed. However, in the mid-infrared, few if any, attempts were made to employ this method.

We report preliminary results of high-resolution scanning photoluminescence experiments in the near and mid-infrared portions of the spectrum. The samples we investigated were Hg_xCd_1-xTe epilayers grown on Zn_0.04Cd_0.96Te and Si/CdTe substrates used in infrared detectors and focal plane arrays. The substrates exhibit photoluminescence from 800 to 820nm, while the epilayer in the 3-5 micron region (depending on the mercury content). To measure mid infrared photoluminescence we modified a commercial FTIR spectrometer and used the double modulation technique. For the near-infrared PL mapping we used a confocal microscope coupled to a grating spectrometer and a CCD camera. The samples were measured at 4.2K (epilayers only), 77K and at room temperature. PL images were compared with X-ray topographs taken at NVESD.

Analysis of the results yields many useful parameters such as the Zn content fluctuation in CdZnTe, and the extent and nature of defects present in the samples. We hope that this technique will find its use in substrate quality control and in improving substrate preparation techniques (polishing, etching) in the growth of infrared detector devices.