Effects of Mg Component Ratio on Photodetection Performance of MgGa₂O₄ Solar‐Blind Ultraviolet Photodetectors

Abstract

Mg x Ga2O4 epitaxial films with different Mg component ratios (x = 0.6, 0.8, 1, 1.1, and 1.4) and their metal–semiconductor–metal solar‐blind ultraviolet (SBUV) photodetectors are prepared on c‐face sapphire by metal–organic chemical vapor deposition (MOCVD). The structure, composition, crystalline quality, and optical properties of the Mg x Ga2O4 thin films have been investigated in detail. It can be found that five Mg x Ga2O4 thin films have the spinel structure with a similar bandgap of ≈5.15 eV, and the highest crystalline quality is observed in Mg x Ga2O4 with x = 1. Besides, photodetector based on Mg x Ga2O4 film with x = 1 has the highest responsivity, the largest UV–visible rejection ratio, and the fastest response speed. As the content of Mg deviates from the stoichiometric ratio of MgGa2O4, the crystalline quality of the Mg x Ga2O4 thin film is reduced, and their photoelectric response characteristics are deteriorated. This work indicates that MgGa2O4 is a promising candidate for the applications in high‐performance solar‐blind ultraviolet photodetectors.

Modeling of Optical Band-Gap Values of Mixed Oxides Having Spinel Structure AB2O4 (A = Mg, Zn and B = Al, Ga) by a Semiempirical Approach

“…Both E f values, derived from different experimental data and techniques, are in good agreement with the value (5.67 eV) calculated by means of eqs 4a–4d, lending further support to the suggested approach. We have to mention that the MGO spinel, in the ground state, has been reported as an inverse spinel ( i = 1), while lower inversion degree values (0.40 < i < 0.88) have been experimentally measured. , From the data of Table , it comes out that, regardless of the inversion degree, the experimentally estimated E f data agree nicely with the band-gap value of n -MGO calculated in Figure by our semiempirical approach. The DFT-based value ( E f = 2.63 eV) calculated by using the generalized gradient approximation (GGA-PBE-modified) greatly differs from the above-reported E f values as well as from experimental optical band-gap values.…”

“…Such an expected trend is also in agreement with the trend observed in band-gap values calculated by using different DFT-based models. 33 For n-MGO samples, fewer experimental optical band-gap values have been reported in the literature, but two recent papers 37,63 report direct optical band-gap values of 5.03 eV for a partially inverse MGO single crystal 37 and of 5.15 eV for an MOCVD film 63 for which the inversion degree was not reported. Older data, pertaining to the electroluminescence properties of MGO samples, provide information on the presence of an exciton energy peak at around 5.25 eV, 39 without any mention of the possible inversion degree, while in the case of a sample, 40 with a partial inversion degree of i = 0.44, an exciton energy peak of about 5.36 eV is reported.…”

Metal–Semiconductor–Metal Photodetectors Based on β-MgGaO Thin Films

“…The highest responsivities of samples A, B, and C are 25.9, 29.88, and 40.88 A/W, respectively, at an incident power density of 1.207 mW/cm 2 . In contrast, responsivities of 6.89, 0.19, and 0.89 A/W were reported for photodetectors based on semiconductors with similar wide bandgaps, i.e., ZnGa 2 O 4 , AlGaN, and MgGa 2 O 4 , respectively.…”

Phase Transition and Bandgap Engineering of MgSnO Thin Films for Solar-Blind Ultraviolet Photodetector Applications

“…In addition, temperature-dependent detrapping of the photogenerated carriers may have played a role. 50 Figure 4j shows dark current and total current under a 265 nm illumination box plot versus different Mg compositions, and the inserted box plot shows photocurrent as a function of Mg compositions. Both dark current and photocurrent decrease with the increase in Mg composition.…”

“…This is reasonable since more photocarriers are generated in the narrower-bandgap materials, contributing to higher photocurrents. As a comparison, other wider-bandgap materials such as MgGa 2 O 4 and AlGaN based photodetectors exhibit a lower responsivity of 0.89 and 0.19 A/W, respectively. Nevertheless, this does not mean that wider-bandgap MgSnO semiconductors are inferior to narrower-bandgap SnO 2 semiconductors for photodetection applications.…”