Pulsed-Mode MOCVD Growth of ZnSn(Ga)N₂ and Determination of the Valence Band Offset with GaN

Abstract

Pulsed-mode metal–organic chemical vapor deposition (MOCVD) growth of ZnSn­(Ga)­N2 on GaN-on-sapphire templates was investigated with the goal of developing stoichiometric, high-quality, epitaxial ZnSnN2-GaN films for integration with GaN-based device structures. It was determined that pulsed-mode growth, during which the Sn precursor was pulsed, enabled the achievement of higher growth temperatures and the avoidance of the formation of Sn droplets, compared to continuous growth. The crystal quality improved with the insertion of a GaN regrown layer prior to the pulsed-mode growth. The stoichiometric ZnSnGa2N4 alloy was achieved with a TMSn pulsing time of 15 s in the 1 min growth loop. The valence band offset (VBO) between ZnSnGa2N4 and GaN was determined experimentally via X-ray photoelectron spectroscopy to be 0.96 ± 0.10 eV. This value is in good agreement with the predicted value of 0.9 eV, assuming a linear dependence of the VBO on the alloy composition. The results from this work will provide additional design freedom based on III-N/II-IV-N2 heterostructures for electronic and optoelectronic devices.