Atomic layer deposition of germanium-doped zinc oxide films with tuneable ultraviolet emission

Thin films of germanium-doped zinc oxide have been deposited by atomic layer deposition. The zinc oxide matrix was grown from cyclic pulses of diethylzinc and water vapour over the temperature range of 100-350 degrees C substrate temperature. Tetramethoxygermanium(IV) was employed as a novel germanium-doping source, which could be incorporated up to 17 at%. At 2.1 at% germanium doping at a deposition temperature of 250 degrees C, the maximum carrier concentration of 2.14 x 10(20) cm(-3) coincides with a carrier mobility of approximately 5 cm(2) V-1 s(-1). No evidence for the formation of nanometre-scale germanium clustering or segregation was observed in the X-ray diffraction patterns or high-resolution transmission electron micrographs of these films. The near band edge photoluminescence shifts to higher energy with increasing germanium incorporation either by the Burstein-Moss mechanism or by alloy formation.