  The growth and elementary properties of p-type Bi2Se3 single crystals are
reported. Based on a hypothesis about the defect chemistry of Bi2Se3, the
p-type behavior has been induced through low level substitutions (1 percent or
less) of Ca for Bi. Scanning tunneling microscopy is employed to image the
defects and establish their charge. Tunneling and angle resolved photoemission
spectra show that the Fermi level has been lowered into the valence band by
about 400 meV in Bi1.98Ca0.02Se3 relative to the n-type material. p-type single
crystals with ab plane Seebeck coefficients of +180 microVK-1 at room
temperature are reported. These crystals show a giant anomalous peak in the
Seebeck coefficient at low temperatures, reaching +120 microVK-1 at 7 K, giving
them a high thermoelectric power factor at low temperatures. In addition to its
interesting thermoelectric properties, p-type Bi2Se3 is of substantial interest
for studies of technologies and phenomena proposed for topological insulators.
