以分子束磊晶法在溝槽結構矽基板上成長氮化鎵之特性研究

Abstract

利用分子束磊晶系統在蝕刻溝槽後的矽基板上成長氮化鎵。首先在矽(110)溝槽中藉由氫氧化鉀的非等向性蝕刻出矽(111)面，接著分別成長25分鐘、50分鐘、75分鐘以及4小時以得到對應厚度為135奈米、280奈米、411奈米及1.48微米之氮化鎵。藉由掃描式電子顯微鏡觀測氮化鎵剖面生成形貌圖，以了解氮化鎵奈米柱在不同磊晶時間下的過程。另外再利用拉曼散射光譜分析氮化鎵的峰值位置及半高全寬之值，搭配變溫光激螢光光譜之訊號，判斷在矽溝槽基板上成長之氮化鎵磊晶品質。最後我們比較氮化鎵成長在三種不同基板的拉曼光譜圖說明具有蝕刻溝槽的矽基板確實能夠得到較好品質的氮化鎵薄膜。

GaN were grown on trench-etched Si substrates by molecular beam epitaxy (MBE). The Si(110) trenches were anisotropic etched into Si(111) plane by KOH solution. The GaN deposition time and thickness are 25 min, 50 min, 75 min, 4 hr and 135 nm, 280 nm, 411 nm, 1.48 µm, respectively. By the observation of scanning electron microscopy (SEM) cross-section view, the growth process of GaN nanorods in different growth time was proposed. The Raman shift and the full width half maximum (FWHM) of the transverse optical (TO) phonon along with the temperature-dependent photoluminescence spectrum were used to evaluate the crystal quality of GaN in Si trenches. By comparing the Raman scattering spectrum of GaN on three different substrates, GaN grown on the trench-etched Si substrates has better crystal quality.