Effect of ZnSe/GaAs interface treatment in ZnSe quality control for optoelectronic device applications

Abstract

We investigate the role of interface initiation conditions on the growth of ZnSe/GaAs heterovalent heterostructures. ZnSe epilayers were grown on GaAs surface with various degrees of As-termination and the application of either a Zn or Se pre-treatment. Structural analysis revealed that Zn pre-treatment of an As-rich GaAs surface suppresses Ga 2 Se 3 formation at the interface and promotes the growth of high crystal quality ZnSe. This is confirmed with lowtemperature photoluminescence. However, moderation of Ga-Se bonding through a Se pretreatment of an As-rich GaAs surface can prevent excessive intermixing at the interface and promote excitonic emission in the underlying GaAs layer. These results provide guidance on how best to prepare heterovalent interfaces for various applications.

Tailoring Heterovalent Interface Formation with Light

“…Thus, the role of illumination before and during the Zn pre-treatment phase is somewhat similar to increasing the substrate temperature, which promotes more interface intermixing. Excessive atomic intermixing at the interface was also observed by our group when growing ZnSe epilayers on GaAs surfaces that had been depleted of As coverage through thermal annealing at temperatures ≥500 °C 2 . In ref.…”

“…In the case of achieving balanced As coverage on the starting GaAs surface to allow some Se passivation while preventing excessive intermixing, it is possible to promote As desorption through elevated temperatures or photon irradiation. However, this would require very precise control of the temperature and time of the desorption process to achieve a favorable As coverage, as demonstrated in our previous work 2 . Moderate light intensities, on the other hand, appear to provide some amount of regulation, allowing control over other growth parameters to be relaxed.…”

“…In ref. 2 , strong Pendellösung fringes were observed when ZnSe epilayer growth was initiated on a fully As-reconstructed surface with a Zn exposure at 300 °C. The predominant mixture of As and Zn atoms suggested that a thin layer (on the order of a monolayer) of Zn 3 As 2 or ZnAs 2 24 may develop at that step, aiding abrupt interface formation.…”

“…The DX and FX emission of the light-start samples is also enhanced with increasing UV lamp power. This effect is likely the result of lower interface recombination, possibly by Se passivation 37 or a stable interface formed through Ga-Se bonds 2 , 36 followed by a high quality ZnSe layer. Based on this result, light stimulated growth of the ZnSe epilayer at 200 °C and a light-start appears to help enhance the underlying GaAs epilayer emission.…”

“…Achieving the optimal distribution of bonds across the interface while minimizing defect formation requires precise control of the interface initiation conditions. For example, point defect and secondary phase formation as well as atomic diffusion between layers can occur during the growth of a ZnSe/GaAs hetero-structure by molecular beam epitaxy (MBE) if the interface is not initiated properly 2 . Such defects would be detrimental to device performance if the heterovalent interface is located between critical layers.…”