氮化鎵之電性研究

Abstract

我們以有機金屬化學氣相沉積法成功製備了氮化鎵半導體薄膜。本研究利用由Van der Pauw發展出方形的平面試片的電阻率量及霍爾量測，氮化物的成長對磊晶條件的變化相當敏感，如緩衝層成長的厚度與退火處理升速率、磊晶溫度、磊晶速率、基版表面氮化處理的溫度和時間、磊晶的V/Ⅲ比。目前，所成長之GaN電子遷移率達300cm2/Vs，電子濃度也降到1017cm-3，已具備p型雜質摻雜的要求。 在蕭基二極體的製作上，我們在氮化鎵薄膜上鍍鈀（Pd）金屬，在室溫下，理想因子為1.115，蕭基能障高□bn(I-V)~0.9eV、□bn(I-V-T)=0.91、□bn(C-V)=1.23。在反向偏壓為-42伏特時，反向漏電流密度為0.236Amp/cm2，其元件相關品質已與世界各主要研究群相當。同時，由暫態電容量測可知，我們可發現氮化鎵之薄膜內存一深植能階，其活化能為0.435eV，濃度較低（5.64×1014cm-3），截面積不大（4.618×10-18cm2），咸信將不至於影響到氮化鎵整個薄膜之光電物理性質。

We has successfully grown the GaN film using metalorganic chemical phase deposition method. From the Van der Pauw and Hall measurement, it is found that the GaN film quality is very sensitive to the growth conditions, such as buffer layer thickness, ramping rate of buffer layer thermal annealing, growth temperature, growth rate, nitridation and V/Ⅲ ratio. Nevertheless, a device quality of GaN film has been obtained. The corresponding carrier mobility as high as 300 cm2/Vs and carrier concentration is lower than 1017 cm-3. Moreover, a schottky diode coated by Pd on n-type GaN was fabricated. The measured ideality factor is of 1.115 and the barrier heights as determined by I-V, I-V-T, C-V measurements are -0.9 eV, 0.91 eV and 1.23 eV, respectively. These values indicate a good quality of our GaN film. In addition, we have found that the GaN films prepared by our group possess a majority-carrier trap located at 0.435 eV below conduction band. Since the trap contration and cross-section are rather low (5.64×1014 cm-3 and 4.618×10-18 cm-2 respectively), we believe this trap will not bring any affections on the performance of GaN devices.