Au/Bi/p-Si蕭基接面變溫I-V及C-V特性研究

Abstract

本研究探討金屬/半金屬/半導體結構中，Au/Bi/p-Si 蕭基接面的變溫電容電壓(C-V)和電流電壓(I-V)電學特性，以及鉍薄膜厚度與溫度對蕭基能障的影響。研究採用分子束磊晶(Molecular beam epitaxy, MBE)技術在p-Si基板上成長不同厚度的鉍薄膜，並利用電子束蒸鍍和反應式離子蝕刻製作蕭基接面元件。在253 K至333 K下進行C-V和I-V量測，C-V量測的結果以空乏近似模型分析接面之蕭基能障、摻雜濃度，探討Bi薄膜厚度和溫度對蕭基能障的影響；I-V量測的結果以指數線擬合得出理想因子、飽和電流，並探討接面主導的電流傳輸機制 C-V測量得到的實驗結果顯示Au/Bi/p-Si蕭基能障值Φb_CV與Si能隙值相當，可能導致 p-Si 表面出現電子強反轉層，且Φb_CV在不同溫度和薄膜厚度下呈現變化，其中Bi層較薄的樣品 (10 nm) 具有更高的能障值(>1 eV)，並呈現隨溫度下降而提升的趨勢。I-V量測得到的實驗結果則發現Bi層厚度為10 nm 和 30 nm 的樣品在低溫下電流主導機制為穿隧輔助復合電流，而厚度增加至100 nm時，電流機制轉為復合電流主導。 本研究說明Bi層厚度與溫度對Au/Bi/p-Si接面的電流機制具有影響，特別是Bi層厚度較薄的Au/Bi/p-Si蕭基二極體，因為對p-Si形成的蕭基能障值相當高，因此展現了實現n-Si歐姆接觸的潛力。

This study investigates the temperature-dependent capacitance-voltage (C-V) and current-voltage (I-V) electrical characteristics of Au/Bi/p-Si Schottky junctions in metal/semimetal/semiconductor structures, as well as the effects of bismuth (Bi) thin-film thickness and temperature on the Schottky barrier height (SBH). Using molecular beam epitaxy (MBE), Bi thin films of varying thicknesses were grown on p-Si substrates, and Schottky junction devices were fabricated through electron beam evaporation and reactive ion etching (RIE). C-V and I-V measurements were conducted in the temperature range of 253 K to 333 K. The C-V measurement results were analyzed using the depletion approximation model to determine the Schottky barrier height and doping concentration, examining the influence of Bi thin-film thickness and temperature on SBH. The I-V measurement results were fitted with an exponential function to extract the ideality factor and saturation current, further exploring the dominant current transport mechanisms in the junction. Experimental results from C-V measurements indicate that the obtained Au/Bi/p-Si Schottky barrier height (Φb_CV) is comparable to the Si bandgap energy, which may lead to the formation of a strong electron inversion layer on the p-Si surface. Moreover, Φb_CV varies with temperature and film thickness, with thinner Bi layers (10 nm) exhibiting higher SBH values (>1 eV) and showing an increasing trend as temperature decreases. The I-V measurement results reveal that the dominant current transport mechanism at low temperatures for the 10 nm and 30 nm samples is tunneling-assisted recombination current, whereas, for the 100 nm sample, the dominant current mechanism transitions to recombination current. This study shows that the Bi layer thickness and temperature have an impact on the current mechanism of the Au/Bi/p-Si junction, especially the Au/Bi/p-Si Schottky diode with a thinner Bi layer, because the Schottky barrier value formed to p-Si is quite high, thus showing the potential to achieve n-Si ohmic contact.