氨氣熱退火處理氮極性面氮化鎵基板之研究

Abstract

本論文主要為氨氣熱退火處理氮極性面氮化鎵基板之研究，熱退火方式共兩種，分別在快速熱退火機台和氫化物氣相磊晶機台，特別的是快速熱退火機台只能在20mtorr下進行。在快速熱退火機台下，以氨氣熱退火且熱退火溫度達900℃時，XRD(002)的半高寬值(FWHM)會下降而AFM量測會產生針狀結構;若改以氨氣加氫氣退火，此時AFM量測會變成峰狀結構。在氫化物氣相磊晶機台下，壓力為700torr且以氨氣加氮氣進行熱退火時，當溫度達到1100℃時，XRD半高寬值反而上升但AFM量測卻相當平整， 本篇研究第二部份探討在熱退火溫度1000℃純氨氣下進行熱退熱火，壓力調變為100torr和700torr，在100torr下，由AFM量測還算平整但在700torr下時會產生不規則孔洞。最後探討氨氣熱退火在不同條件下，表面蝕刻的現象。

In this thesis, we study treatment of N-face GaN substrate by ammonia thermal anneal. There are two ways of anneal respectively in rapid thermal anneal (RTA) and hydride vapor phase epitaxy (HVPE). It is notable that RTA process needs to be carried out under vacuum at 20 mtorr. When annealing temperature of RTA process is up to 900℃ in ammonia ambient, the full width at half maximum (FWHM) value of XRD (002) peak decays and needle-like surface structure is observed by atomic force microscopy (AFM). Comparably, RTA process carries out in a mixed ambient of ammonia and hydrogen forms mountain-like surface structure. Flat surface structure can be also obtained by HVPE at 1100℃ under standard pressure in a mixed ambient of ammonia and nitrogen. On the other hand, the FWHM value of XRD (002) peak increases counter to previous experimental results. The second part of this thesis studies thermal annealing at 1100℃ under vacuum at 100 torr and 700 torr, respectively. The samples annealed at 100 torr possess flat surface structures which are observed by AFM. On the contrary, there are irregular porous structures on the surface of those annealed at 700 torr. In the last part of this study, we also discuss the phenomena of etched surface structures under different annealing conditions.