Fabrication and Characterization of Ga₂O₃Deep UV Photodetector by MOCVD

Fabrication and Characterization of Ga₂O₃Deep UV Photodetector by MOCVD

本研究是利用有機金屬化學氣相沉積MOCVD的技術將寬能隙半導體薄膜氧化鎵(Ga2O3, GaO)且以氧化鎵鋅(ZnGa2O4, ZGO)作為緩衝層(buffer layer)薄膜成長於藍寶石基板，將其應用於深紫外光感測器(DUVPD)。由於以氧化鎵薄膜光感測器的光電流較低，因此選擇利用一層厚度約為10 nm的氧化鎵鋅作為緩衝層(buffer layer)來解決此問題，改善光測器的特性。主要針對氧化鎵薄膜光感測器與以氧化鎵鋅作為緩衝層的氧化鎵薄膜光感測器進行光電特性的比較比較，通過量測得到其光電流、漏電流、光響應時間、拒斥比來比較其特性上的差異。經過研究後發現，以氧化鎵鋅作為緩衝層時可有效提升光感測器的光電流，提升了對於深紫外光波段的響應度，除此之外，在光響應時間與拒斥比等特性上均有所改善，達到了特性優化的目的。

Ga2O3 is a promise deep UV photodetector (PD) due to it’s wide-energy semiconductor property with an energy gap of ~4.9 eV. The photocurrent (IL) of Ga2O3 was achieved to hundreds nA/mm. In this study, the IL of Ga2O3 was enhance by inducted ZnGa2O3 (ZGO) buffer layer during epitaxial growth Ga2O3 by MOCVD. The growth conditions of ZGO buffer listed as Zn/Ga/O2 flow 100/100/500 sccm at 720 0C for 5 min and then ramped the temperature to 825 0C to grow Ga2O3 layer for Ga/O2 flow 40/500 sccm with growth time 60 min. The TEM image shown the thickness of ZGO buffer and Ga2O3 layers were 13 nm and 120 nm, respectively. The photoelectric characteristics of photodetector with MSM type were investigated. The IL( 240 nm, 5V)、rise time/falling time(Tr/Tf)、rejection ratio of Ga2O3 were 750 nA、6.9s/1.4s and 6.5 , respectively. However, the ZGO/Ga2O3 PD were 46.6µA、7.4s/2.6s and 13.3 , respectively. It shown that the IL and rejection ratio were improved very significantly for ZGO/Ga2O3 to Ga2O3 photodetector.