鎂摻雜氮化鎵薄膜離子佈植鈹之特性研究

Abstract

摘要 本論文利用離子佈植鈹到鎂摻雜之氮化鎵薄膜，希望得到高電洞載子濃度的p-type層，有助於低阻值歐姆接觸的製作。鎂摻雜之氮化鎵薄膜是由有機金屬化學氣相沈積法(MOCVD)成長在氧化鋁(Al2O3)基板上，而鈹離子是以50keV、150keV的能量及1013cm-2、1014cm-2的劑量佈植。由光激螢光譜(PL)顯示鎂摻雜的特性仍是主導的，但是鈹離子佈值後出現了與缺陷相關的激發波峰(∼520nm)。而這波峰在1100℃，60秒的快速熱退火處理(RTA)下，呈現明顯變弱的趨勢。另外我們由變溫PL去估計鈹離子佈植後，鎂摻雜的淺階受子能階約為165meV，比無離子佈植樣品的值約250meV降低了30％。而同樣的在1100℃，60秒的 RTA處理下，鈹離子佈植樣品的載子濃度增加到了1.77×1019cm-3，鍍上Ni/Pd/Au歐姆接觸的特性電阻降低到了4.5×10-6Ω-cm2。

Abstract We investigated the characteristics of beryllium implanted Mg-doped p-type GaN. P-type GaN samples were grown on sapphire substrate by metalorganic chemical vapor deposition. These samples were implanted with Be ions for two different doses of 1013 and 1014 cm-2 at different energies of 50 and 150 keV. Photoluminescence measurement was conducted on these implanted samples. After implantation, the luminescence characteristic of Mg dopant still dominates the spectra. Additionally, a broad emission was observed at ∼520 nm and attributed to additional lattice disorders induced by ion implantation. Moreover, a strong recovery of the 520 nm line occurred at annealing temperature of 1100℃ for 60s. Using temperature dependence PL measurement, we estimated the Mg activation energy of about 165meV, which was lower about 30% than the un-implanted samples. The implanted samples also showed an increase from 4.39×1016 cm-3 for as-grown GaN to 1.77×1019 cm-3 at annealing temperature of 1100 oC for 60sec. These results indicated that Be implantation cause lowering of Mg activation energy and increasing the carrier concentration. We measured metal-semiconductor Ni/Pd/Au ohmic contact specific resistivity and the low value of the specific resistivity was obtained to 4.5*10-6 Ω-cm2.