假型高電子遷移率場效電晶體之模擬研究

Abstract

InAlAs/InGaAs 假型高遷移率電晶體在高頻的特性方面是相當優越的，目前已經有許多的團隊做過廣泛的研究並驗證元件電性。為了未來能夠節省成本而順利開發出特性較佳的新元件，模擬的擬合技術變得特別的重要。本研究採用SILVACO公司的TCAD是建立在基礎的半導體物理模擬元件DC特性，並且先使用進階的物理模型來擬合實際的元件電性的趨勢作為模型的驗證，再經由使用的模型參數來擬合其電性的值才能做後續優化趨勢探討。首先要以TCAD來模擬元件在於選對正確的模型即會得到正確的趨勢與結果，所以一開始必須參考文獻來確定InGaAs 低能隙的材料特性高電場時易引發衝擊離子化效應以及InAlAs材料在表面處所形成的未鍵結的負原子形成界面陷阱電荷，再由手冊中選擇對應的模型來模擬元件即可得到正確趨勢。之後，再對相對應之進階模型的參數做校準，使模擬值趨近於實際值。而模型的參數大部分為經驗參數，所以必須自行嘗試完成校準。最後，再藉由改變平面摻雜濃度與磊晶結構進行元件優化的趨勢，優化的磊晶參數有位障層、間隔層、通道層的厚度，來預測元件優化的趨勢。這對於未來開發InAlAs/InGaAs系統的元件有相當大的輔助。本論文的模擬可使開發元件的過程順利且節省時間與成本。

The device characteristics of InAlAs/InGaAs pseudomorphic high mobility transistor is very excellent at high frequency operations. There are already a lot of teams which have done broad research and verify the electrical characteristic of device. In order to save costs and to develop new device effectively with better property in the future, so simulation technology with fitting becomes more and more important. In this study, we adopted TCAD of SILVACO company, based on the foundation of semiconductor physics, to study the DC characteristics of devices by simulation. First we adopted advanced physical models to fit the actual trend of electrical devices as model validation. Then we further use the advanced model parameters to fit the value of electrical properties, which can reveal optimized device trends. If simulate device by using TCAD, we have to choose the correct advanced model built in TCAD to obtain the correct trends and results. Therefore, because that the InGaAs semiconductor is a low band-gap material, we must reference the published papers or documents carefully to determine the properties of InGaAs which could easily lead to induce impact ionization at high electric field. The InAlAs surface would induce numerous negative dangling bond during epitaxy, lead to a lot of interface trap charge generated. Base on this, to get the correct trends of devices simulation, the corresponding model in manual of TCAD must be selected correctly. Then the calibration of the simulation values in the advanced model parameters is required to approach the actual value of device. Most of the parameters of advanced model are empirical parameters, so the user must attempt to complete the calibration in all means by himself. Finally, to optimize device trends we need to manipulate the delta-doped concentration and epitaxial structure, optimize epitaxy parameters of the barrier layer and the spacer layer as well as the channel layer thickness to predict the electrical characteristics of optimized device. It is important to develop the InAlAs/InGaAs system devices in the future with considerable assistance. The achievements of this thesis in simulation would provide key information for device development more effective, more time and cost saving.