X-RAY-DIFFRACTION CHARACTERIZATION OF LPE HGCDTE HETEROJUNCTION PHOTODIODE MATERIAL

High-resolution x-ray diffraction has been used to measure the composi tion difference between P and N layers in HgCdTe heterojunction photod iode material grown by liquid phase epitaxy. The composition (band gap ) difference is a critical parameter in long wavelength photodiodes be cause it affects dark current and the formation of photocurrent collec tion barriers. We find that symmetric 333 reflections cannot resolve t he small composition differences of interest. However, by making use o f the asymmetric 246 reflection, small composition differences (0.03) can be resolved. There is good agreement between rocking curves and se condary ion mass spectroscopy composition depth profiles, both in the value of the composition difference and in the extent of compositional grading in the top layer. High-resolution x-ray diffraction shows pro mise as a nondestructive, relatively rapid technique for screening as- grown heterojunction material for carrier collection barriers.