High-resolution dry etching of zinc telluride: characterization of etched surfaces by X-ray photoelectron spectroscopy, photoluminescence and Raman scattering

A high-resolution dry etching process using a mixture of methane and hydrogen, capable of producing nanostructures less than 70 nm wide in ZnTe, has been developed. Results from XPS measurements of surfaces ZnTe/GaAs epitaxial layers etched at the optimum conductions have indicated that the tellurium oxide has decreased markedly after etching, whereas the zinc oxide has not changed significantly. Marked changes in the photoluminescence spectra of MOVPE-grown ZnTe/GaAs are observed after dry etching. Some of these can be related to reduction in photoluminescence intensity resulting from the hydrogen present in the etch gas mixture. The authors observe an overall reduction in the intensity of the near-band-edge mission by two orders of magnitude encompassing a strong reduction in the intensity of the dominant acceptor bound exciton emission. They also observe a reduction in the intensity of the associated donor-acceptor band (DAP). In addition, they observe new structure in the spectra of the etched samples which lies to lower energy than the DAP emission. After annealing the samples, the near-band-edge emission recovers to about 10% of its original intensity. The deep-level emission of the etched samples changes after annealing and reveals much finer structure. Complementary Raman scattering data on the same samples of ZnTe revealed little overt crystalline damage.