Deep-Ultraviolet Photodetection Using Single-Crystalline β-Ga₂O₃/NiO Heterojunctions

Abstract

In recent years, β-Ga 2 O 3 /NiO heterojunction diodes have been studied, but reports in the literature lack an investigation of an epitaxial growth process of high-quality single-crystalline β-Ga 2 O 3 /NiO thin films via electron microscopy analysis and the fabrication and characterization of an optoelectronic device based on the resulting heterojunction stack. This work investigates the thin-film growth of a heterostructure stack comprising n-type β-Ga 2 O 3 and p-type cubic NiO layers grown consecutively on c-plane sapphire using pulsed laser deposition, as well as the fabrication of solar-blind ultraviolet-C photodetectors based on the resulting p−n junction heterodiodes. Several characterization techniques were employed to investigate the heterostructure, including X-ray crystallography, ion beam analysis, and high-resolution electron microscopy imaging. X-ray diffraction analysis confirmed the single-crystalline nature of the grown monoclinic and cubic (2̅ 01) β-Ga 2 O 3 and (111) NiO films, respectively, whereas electron microscopy analysis confirmed the sharp layer transitions and high interface qualities in the NiO/β-Ga 2 O 3 /sapphire double-heterostructure stack. The photodetectors exhibited a peak spectral responsivity of 415 mA/W at 7 V reverse-bias voltage for a 260 nm incident-light wavelength and 46.5 pW/μm 2 illuminating power density. Furthermore, we also determined the band offset parameters at the thermodynamically stable heterointerface between NiO and β-Ga 2 O 3 using high-resolution X-ray photoelectron spectroscopy. The valence and conduction band offsets values were found to be 1.15 ± 0.10 and 0.19 ± 0.10 eV, respectively, with a type-I energy band alignment.

Ultra‐High Performance Amorphous Ga2O3 Photodetector Arrays for Solar‐Blind Imaging

“…Recently, significant breakthroughs based on different types of Ga 2 O 3 PDs have been reported. [ 6 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ] P‐type semiconductors, such as GaN and NiO, [ 15 , 21 , 22 ] were employed to make p–n heterojunction with Ga 2 O 3 towards photodetection usages. Tang et al.…”

Heteroepitaxial β‐Ga2O3 on Conductive Ceramic Templates: Toward Ultrahigh Gain Deep‐Ultraviolet Photodetection

“…DUV photodetectors incorporating β‐Ga 2 O 3 thin films have been the subject of extensive studies since the introduction of epitaxial deposition techniques for group III‐oxide materials because they enhance photosensitivity and solar‐blind photodetection characteristics. [ 1–3 ] However, previous research has never investigated the hybrid integration of β‐Ga 2 O 3 on transition metal nitride lattice templates, which offers excellent electrical conductivity and catalytic properties. With respect to optoelectronics, most researchers have so far focused on ultrawide‐bandgap group III‐oxides‐based devices grown and fabricated directly on bulk hexagonal phase alpha‐polymorph aluminum oxide (i.e., α‐Al 2 O 3 or sapphire) substrates, [ 4,5 ] which are suitable for hexagonal phase material epitaxy and suffer from considerably lower thermal conductivity and relatively higher thermal expansion coefficients than other inorganic platforms.…”

“…Thus, MgO substrates are an excellent choice for cubic phase material epitaxy, whereas sapphire substrates are more suitable for hexagonal phase material epitaxy. [ 3,28 ] Furthermore, MgO exhibits higher thermal conductivity than that of sapphire. Thus, we anticipate that the hybrid integration of β‐Ga 2 O 3 on TiN lattice templates grown heteroepitaxially on MgO can assist in achieving low‐cost and efficient vertically structured DUV photodetectors if the cubic phase TiN thin film interlayer proves an excellent electrically conductive lattice growth template for monoclinic phase β‐Ga 2 O 3 heteroepitaxial growth, thus causing enhanced photocurrent generation and improved device performance upon light illumination.…”

Single-Crystalline All-Oxide α–γ–β Heterostructures for Deep-Ultraviolet Photodetection

“…The emergence of highly integrated silicon-based photonic platforms has led to extensive applications in the semiconductor and telecommunications industries. However, despite allowing large-volume manufacturing at relatively low cost, the energy bandgap located near 1.14 eV hinders the integration of devices requiring optical transparency in the ultraviolet (UV) and visible regimes, such as visible-light and deep-UV (DUV) photodetectors, [1][2][3][4] group-III-V-based lightemitting diodes, [5][6][7][8] solar cells, 9 electro-absorption modulators, [10][11][12] and transparent thin-film transistors. [13][14][15] Despite significant efforts to realize the heterogeneous integration of the aforementioned devices on silicon-based platforms, [16][17][18][19] challenges related to high defect densities, optical coupling, wafer bonding, and substrate removal remain critical and can lead to consequential overhead production costs.…”