SBIR-STTR Award

Monocrystalline substrate of CdZnTe (4 AT% Zn), nominally lattice matched to HgCdTe (20 AT% Cd), will be prepared from crystals grown by a new process. The new crystal growth system is free of quartz and provides improved growth conditions through 1) temperature profiling and pressure control techniques that cannot be used in conventional growth systems because of temperature and pressure limitations on quartz and 2) removal of comtamination problems related to quartz. It is expected that substrates of high purity, excellent crystal morphology and areas greater than 25 cm will be produced. Characterization will include electron mobility-lifetime profiling by alpha-particle excitation, in addition to standard measurements. Results of the program should demonstrate the importance of a new crystal growth method in preparing high quality substrates of CdTe type materials, provide significant new information related to lattice matching, and increase understanding of the lattice stabilizing effects of alloying.

Keywords:
Crystal Growth Substrates Detectors Arrays Crystal Lattice Morphology Chemical Analys CdZnTe

The main overall objective is to develop a capability for growing 3.0-in (7.6-cm) diameter, 3-kg crystals of CdZnTe suitable for use as substrates for high performance HgCdTe detector arrays. Crystal growth will utilize a new high pressure vertical bridgman method, in which the elimination of quartz, an improved temperature profile and other factors give advantages over other methods. The program will include analysis and modelling, the use of seeded growth to achieve predetermined orientation, and investigations into improving compositional homogeneity. The program will concentrate on a composition of 4 at% Zn, although at least one crystal of 20 at% Zn will be grown as part of the homogeneity investigation. Crystals and wafers will be characterized by an advanced method based on using synchrotron x-rays, in addition to standard methods such as EFD counts, IR analysis and compositional analysis.

Keywords:
Crystal Growth Substrates Detectors Arrays Crystal Lattice Morphology Chemical Analys CdZnTe