臺灣博碩士論文加值系統

本篇論文以MODFET和DHMODFET為模擬元件，利用帕松以及薛丁格方程式進行自洽計算，來找出被侷限在位能井內的二維電子氣體密度。而我們也研究了對於二維電子氣體密度產生影響的幾個因素，包括溫度、間隔區厚度、摻雜濃度、莫爾比例，在這幾個因素中，我們發現二維電子氣體對於溫度的變化並不大，這可減少元件因溫度變化而影響效能表現，而間隔區厚度與摻雜濃度對於二維電子氣體的改變也不大。與摻雜濃度為主要因素的其他Ⅲ-Ⅴ族材料相較之下，Ⅲ-氮族所產生的壓電效應成了影響二維電子氣體的最大因素。而因為採用的是單一電子電洞的等效模型，在考慮多體效應下，我們加入交換關聯位能來做修正。另外我們也發現在gate端施加負壓會抑制MODFET的二維電子氣體產生。

We have used MODFET and DHMODFET as simulation devices. The densities of the two dimensional electronic gas (2DEG) confined in the potential well can be calculated through solving the coupled Poisson and Schrödinger equations self-consistently. We studied some factors might which affect the 2DEG, including temperature, thickness of the spacer layer, doping concentration and mole fraction. We found that these factors have minor effect on the 2DEG.This is good for devices performance. Compared with other Ⅲ-Ⅴ materials, the piezoelectric effect in the Ⅲ-Nitride materials is the major factor to affect the 2DEG. The many-body effect is considered by incorporating the exchange-correlation energy to the Hartree model used for the calculations. And we found that the negative gate bias will reduce generation of the 2DEG.

第一章 序論 1
第二章 原理及方法 3
2-1 元件結構介紹 3
2-1-1 MODFET 3
2-1-2 DHMODFET 5
2-2自發與壓電極化 6
2-3數值計算 10
2-3-1薛丁格與帕松方程式 10
2-3-2異質結構中的邊界條件 14
2-3-3 Gate端控制 18
2-3-4交換關聯位能 19
2-3-5自洽步驟 20
2-3-6材料參數 20
第三章 結果與討論 23
3-1 能帶結構與電子密度的影響因素 23
3-1-1 溫度變化 26
3-1-2 間隔區變化 29
3-1-3 離子摻雜濃度變化 33
3-1-4 莫爾比例變化 35
3-2 MODFET與DHMODFET的交換關聯位能 39
3-2-1 MODFET的交換關聯位能 39
3-2-2 DHMODFET的交換關聯位能 40
3-3 Gate端偏壓下的能帶結構與電子分布 42
第四章 結論 44
參考文獻 45

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