氮化鎵蕭基二極體電性研究

Abstract

本文是以不同的量測方法研究利用有機金屬氣相磊晶法 成長氮化鎵薄膜 所製成蕭基二極體之電性。利用電流-電壓量測得知電 流傳導機制是由熱場發射電流所主宰(五╱三比愈高愈明顯)，順偏穿遂電 流發生原因為表面區域離子化粒子濃度很高。逆偏時，逆偏大為直接穿遂 蕭基能障高 ；逆偏小時則藉由缺陷穿遂較小的能障。 電容- 偏壓量測得知五╱三比愈小，氮空位增多，載子濃度變多，因此串聯電阻 變小，電容變大。蕭基能障高 在低溫時比理論值0.84eV高出許多，且隨 溫度升高而變小。以深能階暫態電容量測分析，結果顯示E2缺陷可能為 NGa造成，E3缺陷可能為OGa造成。另外發現一個新的缺陷E4，其形成原因 需再做進一步觀察確認。 In this study, several measurement techniques were used to analyze the electric characteristics and traps in unintentionally doped n-type GaN grown by metal organic chemical vapor deposition.I-V measurements on Schottky diodes indicates the forward current appears due to thermionic field emission of electrons through the Schottky barrier, because there are high trap concentrations near the surface region. On the other hand, the electrons tunnel through the Schottky barrier at large reverse voltage, and through a smaller barrier by the assistance of a trap E2 at small reverse voltage. C-V measurements indicate the smaller V/III ratios, the larger carrier concentrations because of the increase of nitrogen vacancies. Therefore,the series resistance becomes smaller and capacitance larger. Schottky barrier height is much larger than the theoretical value of 0.84eV at low temperature, and is smaller at high temperature. Studies by transient capacitance measurements revealed the presence of a new majority-carrier trap with the activation energy of 1.34eV.