During the past four years the yield of high-resolution mercuric iodide (HgI2) gamma ray spectrometers produced at EG&G/EM has increased dramatically. Data are presented which demonstrate a strong correlation between starting material and spectrometer performance. Improved spectrometer yields are attributed to the method of HgI2 synthesis and to material purification procedures. Data are also presented which show that spectrometer performance is correlated with hole mobility-lifetime products. In addition, the measurement of Schottky barrier heights on HgI2 spectrometers has been performed using I-V curves and the photoelectric method. Barrier heights near 1.10 eV have been obtained using various contacts and contact deposition methods. These data suggest the pinning of the Fermi level at midgap at the HgI2 surface, probably due to surface states formed prior to contact deposition.