同電子性砷摻雜及離子佈植氮化鎵薄膜之光性研究

Abstract

在本論文中，我們利用拉曼光譜（Raman）、冷激光光譜（PL）、冷激光激發光譜（PLE）、原子力顯微鏡（AFM）等方法研究成長在氧化鋁（Al2O3）基板上之氮化鎵摻雜及離子佈植同電子性砷的光學性質及晶格結構。同電子性摻雜，普遍認為有修復晶格，以及改善光學性質的功能，於是我們比較利用長晶時通TBAs氣體的摻雜方式和利用砷離子佈植再以RTA退火修復的兩種方式對樣品的光學性質上有何不同的影響。關於摻雜方式的樣品，在PL的結果中，我們觀察到隨通入TBAs流率的增大I2發光譜半高寬有變窄的趨勢。以及XRC（X-ray rocking curve）對於GaN(0002)面的34.7度波峰半高寬也有變窄的趨勢，另外AFM的結果顯示隨流率的增加表面趨於平緩，這些現象我們歸因於同離子性砷摻雜的結構重整效應。關於離子佈植砷的樣品，我們觀察到不一樣的效應，經退火的過程會形成∼475nm的發光譜其強度隨退火的時間逐漸增加。推測此發光波長的成因，為As原子經退火的過程會逐漸佔入因離子佈植過程中產生的Ga空缺而形成AsGa，這樣的缺陷產生的deep double donor能態是形成∼475nm放射光的原因。在濃度為1019cm-3的樣品中，退火20秒表現最大的I2/YL比值，顯示晶格恢復的較好。最後，我們對於退火前與退火後樣品測量在YL的PLE激發波長的吸收效應，在室溫時PLE的波峰與I2的位置皆有紅移的現象，推測此現象很可能是佈植過程產生的GaI的缺陷所致，同時退火的過程並不能完全修復此種缺陷。而這樣的缺陷能階同樣也是產生YL的另一個管道。

In this thesis, we used experimental techniques, such as Raman spectrum, PL, PLE, AFM etc. to analyze the optical properties and crystal structures of GaN grown on sapphire (Al2O3) that was implanted and doped by isoelectronic arsenic. Isoelectronic doping has been demonstrated to repair the crystal and improve the optical properties. We examine the effects on optical properties by two doping methods, one by flowing TBAs to furnace during epitaxy and the other by implanting arsenic ions into samples and followed by RTA process. About doped samples, we observed the narrowing FWHMs of I2 in PL with increasing TBAs flow rate. The XRC (X-ray rocking curve) of GaN(0002) surface about the 34.7 peaks also shows the decreasing FWHM. Besides, the AFM results reveal shows the decreasing FWHM, the smoothed surface. These phenomena suggest that the isoelectronic arsenic doping can help reconstruct the structure. For the implanted samples, different effects were observed. After the RTA process, the luminescence intensity around 475 nm became stronger with the RTA duration. We conjecture that the luminescence is due to, the arsenic atoms occupying the gallium vacancies formed by the implanting process so that the AsGa is formed. Such a defect type is deep double donor which accounts for the luminescence around 475 nm. When the sample’s concentration is 1019cm-3, it has the largest I2/YL ratio under 20 seconds RTA. Finally, we measured the PLE of samples before and after RTA process, the PLE peak shows red shift compared to I2 at room temperature. It is proposed that GaI defect can be formed by ion implantation process and cannot be recovered by RTA process. This kind of defect can also be another channel forming YL luminescence.