利用雙加熱式有機金屬化學氣相磊晶系統成長高銦氮化銦鎵薄膜與其物理特性研究

Abstract

本論文中，我們利用雙加熱式有機金屬化學氣相磊晶(two-heater metalorganic chemical vapor deposition, two-heater MOCVD)系統，藉由改變成長溫度、石墨盤轉速、以及TMGa莫耳流率成長氮化銦鎵(InxGa1－xN)薄膜。在改變成長溫度系列，以傳統MOCVD為例，氮化鎵(GaN)之磊晶效率(growth efficiency)不隨溫度改變，是因為其成長溫度範圍為GaN之質傳作用區，而對於氮化銦(InN)之磊晶效率而言可以區分為兩個區域，在675℃以下其磊晶效率維持定值不變，而在675℃以上，其磊晶效率因為InN解離而下降，其解離活化能利用阿瑞尼斯曲線擬合為0.885 eV，同樣在雙加熱系統下其活化能擬合結果一樣為0.885 eV，認為傳統與雙加熱系統都是因為表面溫度使得InN磊晶效率下降，並利用改變石墨盤轉速系列證明此結果。 在改變TMGa流率方面，TMGa莫耳流率由9 μmol/min降低至6 μmol/min，固相銦組成可由0.28增加至0.50，且低溫光激螢光光譜能量從1.87 eV降至1.44 eV，已突破目前成長InGaN薄膜時所碰到紅外線間隙區(infrared gap region)的瓶頸。而當TMGa莫耳流率由6 μmol/min降低至3 μmol/min，其固相銦組成卻由0.50降至0.34，推論是受到捕捉效應(Trapping effect)的緣故，另外在TMGa流率為3 μmol/min時，薄膜出現In(101)訊號，可能是由於NH3分解不足，或成長速率過慢，成長區域接近熱力學平衡導致相分離的緣故。

In this theis, three series of InxGa1－xN films were grown by two-heater metalorganic chemical vapor deposition (two-heater MOCVD) system. They are varying growth temperature series, varying graphite disk rotation series, and varying trimethylgallium (TMGa) flow rate series. For varying growth temperature series, take conventional MOCVD for example, GaN growth efficiency is independent of temperature. This is attributed to GaN growth in mass-transport region in this temperature range. For InN growth efficiency, it can separate from 2 region, below 675℃, InNgrowth efficiency is independent of temperature; above 675℃, InN growth efficiecncy decreases with reducing growth temperature, owing to the decomposition of InN. And the activation energy of decomposition of InN is 0.885 eV by fitting the Arrhenius equation. By using two-heater MCVD system growth InGaN films, we obtain the same activation energy value. We considered that InN growth efficiency descreases by surface temperature rather than ceiling temperature. The result was proven by the experiment of varying graphite disk rotation series. For varying TMGa flow rate series, the TMGa molar flow rate decreased from 9 μmol/min to 6 μmol/min, the solid indium (In) content increasing from low In content 0.28 to high In content 0.50, and the emission energy decreasing from 1.87eV to 1.44 eV. We have surmounted the technique bottleneck of the infrared gap region of InGaN epilayer. And for the TMGa molar flow rate decreased from 6 μmol/min to 3 μmol/min, the solid indium (In) content rather decreasing from In content 0.50 to 0.34, is attributing to the trapping effect. Otherwise, as the TMGa molar flow is 3 μmol/min InGaN sample, the In(101) single appear from X-ray diffraction experiment. We speculate that the deficiency of NH3 cracking efficiency or the low growth rate, which result that thermodynamic condition toward more equilibriumlike.