Boron arsenide thin film solar cell development

Pyrolytic decomposition of diborane and arsine was used in attempts to grow polycrystalline BAs films. This method produced only amorphous films for deposition temperatures below 920 C and polycrystalline boron subarsenide (B12As2) films for deposition temperatures above this value. The amorphous films were determined to have a significant arsenic content but the actual stoichiometry was not obtained. The films were adherent on single crystal sapphire (0001), (111) silicon, (0001) SiC, and polycrystalline SiC but were found not to be adherent to substrates of fused quartz, tungsten, and molybdenum. It was also found that all films deposited above 650 C were p-type while those deposited below 600 C were usually n-type. Polycrystalline BAs and B12 As2 was produced by reaction of the elements in a closed tube. Reflectance data on the amorphous films indicate a probable additional optical transition between 3.0 and 3.5 eV. Measurements of a capacitor structure using a polycrystalline BAs pressed pellet gave an index of refraction of 1.9 at 15 KHz. Infrared studies show a possible significant amount of boron hydrogen bonding along with evidence indicating carbon hydrogen bonding.