Electronic Properties of Vertically Stacked h-BN/B_{1- x}Al_xN Heterojunction on Si(100)

Hexagonal boron nitride (h-BN) exhibits a dangling bond-free layered structure and ultrawide band gap, which is apt to integrate with other semiconductors to form a heterojunction. Particularly, heterojunction structure is the main impetus for h-BN to broaden the horizon on deep ultraviolet optoelectronic and photovoltaic applications. Here, a series of h-BN/B_1-xAl_xN heterojunctions with different Al components were fabricated by radio frequency (RF) magnetron sputtering. The performance of h-BN/B_1-xAl_xN heterojunction was measured via I-V characteristic representation. The sample of h-BN/B_0.89Al_0.11N heterojunction was the best one due to the high lattice matching. Moreover, a type-II (staggered) band alignment was formed in this heterojunction which was elucidated by X-ray photoelectron spectroscopy (XPS). The calculated valence band offset (VBO) and conduction band offset (CBO) of h-BN/B_0.89Al_0.11N are 1.20 and 1.14 eV, respectively. The electronic properties and formation mechanism of h-BN/B_0.89Al_0.11N heterojunction were further studied by density functional theory (DFT) calculation. The existence of a built-in field (E_in) was confirmed, and the E_in direction was from the BAlN side to h-BN side. The staggered band alignment was further verified in this heterojunction, and an Al-N covalent bond existed at the interface from calculated results. This work paves a pathway to construct an ultrawide band gap heterojunction for the next-generated photovoltaic application.