獨立式氮化鎵不同極性面對於金屬半導體接面的影響

Abstract

本實驗主要想探討「在具有極性的C方向獨立式氮化鎵基板上製作金半接面，不同極性面對於接面的影響」。本實驗使用的是由HVPE磊晶，再以Laser Lift Off剝離，形成的獨立式氮化鎵基板。 首先比較不同極性面對金半接面的差異，結果顯示製作於Ga-face的蕭特基接觸相對N-face的樣品有著更高的蕭特基位障，而製作在N-face的歐姆接觸對於Ga-face的樣品有更低的電阻，我們嘗試用極性影響能帶彎曲來解釋以上現象；之後比較「高溫熱退火對不同極性面歐姆接觸的影響」，發現退火可以有效改善製作於Ga-face的歐姆接觸，卻對N-face的樣品沒有影響，推論是接面處TiN的產生；此外也發現表面平整度的改善可以提升金半接面的表現。

Un-doped epitaxial GaN layers with Ga- and N-face polarity were grown by Hydride Vapor Phase Epitaxy (HVPE) in order to characterize the influence of polarity on the electrical properties of metal-semiconductor contact. Compared with N-face sample, the Ga-face sample exhibited higher Schottky barrier height of Ni/Au-based Schottky contact. Compared with Ga-face sample, the N-face sample exhibited lower resistance of Ti/Al/Ni/Au-based Ohmic contact. By high temperature annealing, the Ga-face Ohmic contact will be improved, but the N-face sample not. A possible explanation for this behavior can be a different band bending of the conduction and valence band, inferred from the different spontaneous polarization in epitaxial layers with different polarity. Furthermore, We also investigate the influence of surface roughness on Schottky contact.