Chemically assisted vapour transport for bulk ZnO crystal growth

摘要

A chemically assisted vapour phase transport (CVT) method is proposed for the growth of bulk ZnO crystals. Thermodynamic computations have confirmed the possibility of using CO as a sublimation activator for enhancing the sublimation rate of the feed material in a large range of pressures (10~(-3) to 1 atm) and temperatures (800-1200 ℃). Growth runs in a specific and patented design yielded single ZnO crystals up to 46 mm in diameter and 8 mm in thickness, with growth rates up to 400 μm/h. These values are compatible with an industrial production rate. N type ZnO crystals (μ=182 cm~2/(Vs) and n=7 10~(15)cm~(-3)) obtained by this CVT method (Chemical Vapour Transport) present a high level of purity (10-30 times better than hydrothermal ZnO crystals), which may be an advantage for obtaining p-type doped layers ([Li] and [Al] < 10~+(15) cm~(-3)). Structural (HR-XRD), defect density (EPD), electrical (Hall measurements) and optical (photoluminescence) properties are presented.