High signal/noise ratio deep UV detector with maximum response at 230 nm based on mix-phase MgZnO deposited under high laser energy condition

Abstract

Mix-phase MgZnO thin film was fabricated on the c-plane sapphire substrate (Mg0.4Zn0.6O target) under high laser energy density condition by the PLD method. The internal quantum efficiency of the detector based on the mix-phase MgZnO thin film at 230 nm deep UV light reached 86% at 40 V bias voltage. And the Iuv(230 nm)/I dark ratio of the MgZnO detector reached 864 at 40 V bias voltage, which is mainly caused by both the higher internal gain of the detector at deep UV light and its smaller I dark . The high internal gain of the detector is mainly due to the higher density of interfaces between the different structure of MgZnO grains in the mix-phase MgZnO thin film, which is caused by the higher laser energy density deposition condition certified by contrast experiments. The small I dark of the detector is mainly caused by the higher barriers in the mix-phase MgZnO thin film and more cubic MgZnO in the mix-phase MgZnO thin film, and higher laser energy density deposition condition and O-rich c-plane sapphire substrate surface are key factors, which also agree with the contrast experiments results. So when the mix-phase MgZnO thin film that is constituted by both a small number of narrower band gap hexagonal MgZnO and a large number of wide band gap cubic MgZnO is used in the deep UV detector, and the difference in band gaps between different structures of MgZnO is relatively higher, a higher signal/noise ratio of the device at 230 nm deep UV light is gained, which is meaningful for developing high-performance deep UV detection technology.

Transport Mechanism of Enhanced Performance in an Amorphous/Monoclinic Mixed-Phase Ga2O3 Solar-Blind Deep Ultraviolet Photodetector

“…To maintain the equilibrium of the mixed-phase interface Fermi level, the electrons in the crystalline Ga 2 O 3 will migrate to the amorphous Ga 2 O 3 , thereby inducing the energy levels near the amorphous Ga 2 O 3 bending upwards to form a built-in electric field (space charge region) around the interface. When two parts finally reach the same E f , the built-in electric field from the crystalline phase to the amorphous one will prevent the further diffusion of charges [10,28].…”

“…Ga 2 O 3 is a natural n-type oxide semiconductor material [2,3,70]. According to the traditional theory of n-n heterojunction, the bias voltage applied to wide bandgap semiconductor is predominantly concentrated at the interface between different phase parts [28]. Since the crystalline and amorphous domains of mixedphase Ga 2 O 3 are considerably small, V 1 and V 2 are, respectively, approximated as the voltage applied to the interface between crystalline and amorphous domains.…”

“…Recently, mixed-phase semiconductor materials have been used in photodetectors, such as c-ZnMgO/w-ZnMgO, and others [10,28,29]. According to previous reports, PDs based on mixed-phase ZnMgO have been demonstrated to be able to achieve both higher responsivity (meaning higher photocurrent) and lower dark current, compared with singlephase structure devices [10,28,29]. For the Ga 2 O 3 material, its different polymorphs are usually reported, namely α, β, γ, δ, ε, and even amorphous phase [1,30].…”

“…To maintain the equilibrium of the mixed-phase interface Fermi level, the electrons in the crystalline Ga2O3 will migrate to the amorphous Ga2O3, thereby inducing the energy levels near the amorphous Ga2O3 bending upwards to form a built-in electric field (space charge region) around the interface. When two parts finally reach the same Ef, the built-in electric field from the crystalline phase to the amorphous one will prevent the further diffusion of charges[10,28].The dark current transport process of mixed-phase Ga2O3 PD under a bias of 5 V is shown in Figure5b. In general, a large number of oxygen vacancies acting as donor states in the amorphous Ga2O3 is beneficial for prolonging the life of electrons and inducing…”

Unleashing the Power of Quantum Dots: Emerging Applications from Deep‐Ultraviolet Photodetectors for Brighter Futures

“…[14][15][16] To overcome the above-mentioned issue, it is essential to use ultra-wide band gap (UWBG, bandgap over 3.4 eV) materials as photoactive substances beyond wide band gap (WBG, bandgap exceeds 3.1 eV) materials. In the past decades, various studies have reported DUV PDs using UWBG materials such as Ga 2 O 3 , [17][18][19] Mg x Zn 1-x O, [20][21][22] Al 1-x Sn x O, [23] III-nitrides (Al x Ga 1-x N, [24][25][26] AlN, [27][28][29] and BN [30][31][32] ), and diamond. [33][34][35] The high crystalline UWBG semiconductors provide the narrowband photo response based on bulk charge generation through the incident wavelength near optical bandgap.…”