p型氮化鎵歐姆接觸的研究

Abstract

本實驗利用不同合金金屬結構製作p型GaN薄膜的歐姆接觸，希望藉由摻雜的元素降低特性電阻。 利用Au/Pd/p-GaN結構得到了p型GaN薄膜表面處裡的標準步驟，並且得到的特性電阻為9.6 × 10－4Ωocm2 ，這是我們所得到最佳的歐姆接觸。比較AuZn/Ni/p-GaN與Au/Ni/p-GaN兩種不同結構所得到的歐姆接觸， 發現Zn的存在能有效的降低特性電阻。其特性電阻為1.03 × 10-2Ωocm2。 研究AuBe/Ni/p-GaN的歐姆接觸發現Be可能會形成晶隙的缺陷，而大幅的提高特性電阻。在低溫PL光譜發 現Be所造成的波峰位置在391nm。至於其真正的發光機制則需要再做進一步的研究。

In this dissertation , severial kinds of metal schemes were used to form ohmic contacts on p-GaN. In this work ,ohmic contact to p-type GaN with the lowest contact resistivity of 9.6 × 10－4Ωocm2 was developed by the surface treatment prior to Pd/Au metal deposition. Compared the metal schemes of AuZn/Ni/p-GaN andAu/Ni/p-GaN.It is observed that the Ni dissociates at the p-GaN surface and this dissociation promotes the Zn diffusion upon heat treatment.So the existance of Zn does effectionlly lower the contact resistivity(1.03 × 10-2Ωocm2). Investigation new metal scheme of AuBe/Ni to p-GaN have been carried out.It is observed that the contact resistance drastically increase as the annealing temperature excess 550℃.This result indicated that the diffusion of Be atoms into the p-GaN layer would increase the resistance of the layer.The behavior of the Be atoms in the p-GaN layer would be like as a lattice defect, such as interstitial impurities.To explore the origin of Be atoms in the p-GaN layer.The PL measurements were performed at 10K.The emission(3.17eV) of DAP is attributed to the shallow donors level(at about 30meV below the conduction band) and the Be-related deep level impurities(at about 262meV above the valence band)