Growth and characterization of Br-doped ZnSe single crystals grown by a vertical sublimation method

Abstract

Bromine doping of ZnSe single crystals grown by using a vertical sublimation method was studied. ZnBr 2 was used as a dopant at concentrations of 0.003 to 0.1 mg/cm 3 in the ampoules. When the Br-doping was 0.01 mg/cm 3 or less, the average growth rate of the crystals was about 34 mg/h cm 2; the same as that without doping. When the Br-doping exceeded 0.01 mg/cm 3, the average growth rate decreased with increasing dopant concentration. The undoped ZnSe crystals were yellow, whereas the Br-doped ZnSe crystals were orange. The high quality of the grown crystals was confirmed by X-ray diffraction (XRD), which showed that the full width at half maximum (FWHM) of the rocking curve ranged from 6.7 to 8.9 arcs. Bromine concentration of the grown crystals ranged from 4×10 17 to 1.5×10 19 cm −3 (measured by secondary ion mass spectrometry, SIMS), depending on the dopant concentration. All of the as-grown crystals showed high resistivity. After growth, all of the grown crystals were annealed in a Zn atmosphere at 1100°C for 100 h to activate the bromine as an n-type donor. When the dopant concentration was increased, the carrier concentration of Br-doped ZnSe increased from 1.4 to 4.1×10 17 cm −3 and the mobility decreased from 366 to 146 cm 2/V s (determined by Hall effect measurements). Our results show that high quality, low resistivity ZnSe single crystals can be grown by this vertical sublimation method.