A Strategy to Eliminate Selenium Oxide Islands Formed on the ZnSe/GaAs Epilayer: Article No. 108176

Atomically clean and smooth surfaces are essential for semiconductor device fabrication and epitaxial regrowth. In this regard, spontaneously formed oxide islands or clusters on the surfaces of II-VI semiconductor exposures to air can disrupt interface formation. Using ZnSe/GaAs heterostructures grown by molecular beam epitaxy (MBE), we investigated the effect of surface treatments in eliminating oxide islands. The samples were probed with atomic force microscopy, low-temperature photoluminescence, and scanning electron microscopy. It was found that ultra-high vacuum (UHV) annealing at 200 degrees C, regardless of annealing duration, largely removed the islands while leaving the crystallinity of the ZnSe and GaAs epilayers unaffected. UHV annealing at higher temperatures of 300 degrees C completely removed the islands, but the optical properties of ZnSe and/or GaAs epilayers deteriorated depending on the annealing duration. Our observations provide guidance to set thermal annealing strategies for removing oxide islands from the surfaces of II-VI/III-V semiconductor heterostructures depending on the desired properties.