P型氮化鎵金/鉭/金歐姆接觸特性研究

Abstract

本論文對Au/Ta/Au/p-GaN歐姆接面進行一系列有系統的研究，主要依據是利用鉭進行表面為氧化層再清理的動作，以降低蕭特基位障，我們利用金/鉭/金這種方式，將鉭夾於上下金薄膜之中，讓其更易於形成網狀結構，使得兩層之金原子得以互相擴散，並主導金半接面電流傳輸特性。實驗結果為退火前及退火後金/鉭/金近似線性，而阻值在高溫（700℃以上）時急遽降低，我們認為高溫阻值降低之效應可能與鉭氫鍵結有關。因為在高溫時部分鉭的氧化物預期會漸漸解離，釋出鉭原子和表面的氫鍵結，使得金屬與半導體接面附近的電洞濃度上升，增加穿隧電流。

We have studied a set of the ohmic contact of p-type GaN using alloy. The intended use of Tantalum (Ta) in this study is because of its capability of removing native oxide of GaN epilayer. So that the carrier transport can be greatly improves. This Ta-layer is sandwiched in between the gold (Au) layers, so that after the post-annealing the inter-diffused Au can form a type of meshed structure to improve the Ohmic property. It is interesting to note that the resistance of Au/Ta/Au contact found to drop. Significantly for annealing temperatures above 700℃, which is believed to relate with hydrogenation effects of Tantalum oxide. It results in an increment of the surface hole-density and hence the tunneling-current density. Since Ta metal exhibits good adhesion property and high thermal stability, the structure of Au/Ta/Au Ohmic contact may potentially useful in the applications of high-temperature and high-power GaN devices, such as white LED.