Β-Ga2O3 solar-blind deep-ultraviolet photodetector based on annealed sapphire substrate. (June 2017)

• Record Type: Journal Article
• Authors: Qian, L.X.; Wang, Y.; Wu, Z.H.; Sheng, T.; Liu, X.Z.
• Is Part Of: Vacuum. Volume 140(2017)
• Page Start: 106
• Page End: 110
• Publication Date: 2017-06
• Subjects: Vaccum annealing -- Sapphire substrate -- β-Ga2O3 -- Solar-blind deep-ultraviolet photodetector -- Molecular beam epitaxy; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2016.07.039
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: A vacuum annealing was conducted on c-plane sapphire substrate in a plasma-assisted MBE system prior to the epitaxial growth of β-Ga2 O3 film. Accordingly, both the crystal structures of epitaxial films and the device performance of fabricated metal-semiconductor-metal photodetectors were comparatively investigated based on the as-supplied and annealed sapphire substrates. The AFM result showed a large number of protrusions distributed uniformly on the surface of annealed sapphire substrate, proving an effective high-temperature reconstruction by such a pretreatment. Moreover, the β -Ga2 O3 epitaxial film exhibited a significantly improved crystalline quality by adopting the annealed sapphire substrate as revealed by the XRD measurement. Accordingly, the carrier mobility could be improved due to the suppression of impurity scattering related to structural disorders, resulting in the observed significant increase of both dark and photo currents in photodetector. As a result, its DUV responsibility was improved from 44 A/W to 153 A/W. However, some degradations in photo-to-dark current ratio and response time appeared, which can be attributed to the reduction in the crystallographic defects impacting internal gain and carrier recombination, respectively. This work may pave an alternative way for the fabrication of high-performance β -Ga2 O3 solar-blind DUV photodetector, especially for high responsibility. Highlights: The AFM result showed many protrusions distributed uniformly on the surface of annealed sapphire substrate. The improved crystalline quality by adopting annealed sapphire substrate was revealed by the XRD measurement. The significant increase of both dark and photo currents in MSM photodetector was observed. The DUV responsibility of MSM photodetector was improved from 44 A/W to 153 A/W under a bias voltage of 20 V. Some degradations in photo-to-dark current ratio and recovery time appeared.