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

Abstract

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 °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 °C, the maximum carrier concentration of 2.14 × 10²⁰ cm⁻³ coincides with a carrier mobility of approximately 5 cm² 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.