Selective area molecular beam epitaxy over patterned ZrO2 and HfO2

Selective area growth is a promising approach to the seamless integration of dissimilar materials for (opto)electronic devices, yet historically most work in this area has focused solely on conventional SiO2 masks. Expanding the palette of embedded dielectrics could unlock new applications, functionalities, and hybrid structures. Here, we demonstrate selective growth of GaAs over patterned ZrO2 and HfO2 features by molecular beam epitaxy for the first time. Complete selectivity is achieved over both ZrO2 and HfO2 at approximately half of the flux that can be employed for complete selectivity on an SiO2 mask due to higher adatom desorption probabilities on SiO2. Faceting in GaAs grown selectively within ZrO2 gratings is found to depend on the crystallographic orientation of the mask patterns, which is consistent with GaAs grown selectively within nominally identical SiO2 structures. In particular, growth within [010]-aligned structures induces the formation of {101} planes that are well-suited for epitaxial lateral overgrowth and coalescence for seamless mask encapsulation. The identified selective growth conditions enable complete selectivity over ZrO2 and HfO2 features of any arbitrary size and can likely be extended to HfZrO2 alloys of any composition. This work demonstrates the generality of selective molecular beam epitaxy over dissimilar mask materials and highlights the emerging possibilities of seamlessly incorporating functional oxides beyond SiO2 that exhibit novel properties such as the Pockels effect, ferroelectricity, and optical nonlinearity. Specifically, we show a scalable approach to the integration of III–V alloys with HfZrO2 dielectrics toward three-dimensionally structured devices and integrated systems.