以第一原理與量子傳輸來計算在1nm接觸寬度的鎳鍺化物與N型鍺接面

Abstract

本論文以第一原理及量子傳輸計算探討「鎳鍺合金/鍺」蕭特基接面，並計算釩離子植入在不同位置對電子蕭特基能障與特徵接觸阻抗造成的影響。首先，我們藉由X-射線繞射分析實驗樣本，選擇鎳鍺合金訊號較強的晶面進行初步的計算。經由考量計算資源，最終選定建構NiGe(112)/Ge(100)接面來作更進一步的分析。其次，過去研究曾以第一原理計算數種離子植入對NiGe/Ge蕭特基位障的影響，其中Se離子、V離子明顯地降低蕭特基位障。由於Se離子已有許多文獻研究，本論文將針對V離子進行後續計算。 隨著金屬半導體接面面積微縮，植入離子不一定會位於NiGe/Ge介面，有可能偏離NiGe/Ge介面，我們必須考量一個包含NiGe/Ge介面及介面周圍材料的超晶胞。就模擬的方面，我們建立極窄NiGe/Ge接面並且以模型絕緣層ZnS夾住NiGem。除了使用ZnS當作模型絕緣層，我們還另外計算以真空為模型絕緣層並觀察蕭特基位障的變化。我們也探討特殊離子V植入在NiGe/Ge介面以及偏離NiGe/Ge極窄介面時對蕭特基位障的影響，並經由非平衡格林函數進行電性計算，討論V離子植入在NiGe/Ge介面及偏離介面時接觸阻抗的變化。

In the thesis, we perform first-principles and quantum-transport calculations to study the Shottcky barrier height and specific contact resistance, respectivly, of the NiGe/Ge contact with V ion implanted at various substitutional sites. First, we figure out the Ni-germanide compositions and crystalline planes from the XRD analysis, and initially construct the NiGe/Ge contact structures with several NiGe crystalline planes of the stronger peak signals. After considering our available computing resources, we finaly choose and build NiGe(112)/Ge(001) as our modeled structure for simulation. Second, in the past research, we have calculated by first-principles the Schottky barrier height of the NiGe(112)/Ge(001) contact under the influence of several implanted ions. Our previous calculations show that Se and V ions significantly reduce the Schottky barrier height. Because the implanted Se ion has been studied extensively, we will be focused on V in this study.

As the contact area scales down, implanted ions are not necessarily located at interface and may reside outside of the contact area, we build a model structure of a narrow NiGe slab in side contact with a Ge surface, and the NiGe slab is sandwiched between our modeled “insulator” ZnS. We change the modeled “insulator” from ZnS to vaccum and see how the Shottcky barrier heights are affected. We also compare the Shottcky barrier heights and contact resistance with the V ion located within and out of the contact area.