石墨烯應用於深紫外光發光二極體上作為透明電流擴散層

Abstract

石墨烯(graphene)為一種由碳原子依六角形排列而成之二維碳材料，其具有良好之電子遷移率、熱傳導度、機械特性與低片電阻等特性，而其於波長小於280奈米之高穿透度更被看好應用於深紫外光發光二極體(GaNLED)之上作為透明電流擴散層(TCE)。然而，石墨烯和GaN（特別是p-GaN）之間的高接觸電阻率(ρc)成為利用石墨烯作為GaNLED的透明電流擴散層需要解決的重大困難。 為了降低石墨烯和GaN介面的接觸電阻率，在本實驗中，我們準備了兩種類型的緩衝層包括氧化鎳(NiO)薄膜和銦錫氧化物(ITO)量子點放置於石墨烯和GaN之間，藉以增進石墨烯和GaN之附著力，並降低其介面的蕭特基能障。本實驗乃利用低壓化學氣相沉積(Chemical Vapor Deposition；CVD)方法製作石墨烯，p-GaN磊晶則由晶元光電所提供。其中厚度為2 nm之氧化鎳乃利用原子層化學氣相沉積法(Atomic Layer Deposition；ALD)將其沉積於石墨烯與p-GaN之間，另一緩衝層為於石墨烯與p-GaN間鍍層銦錫氧化物薄膜經蝕刻過後使之成為量子點銦錫氧化物。置入緩衝層後再以450°C氬氣環境下熱退火處理以加強結構完整性，最後利用圓形傳輸線模型(circular transmission line model；CTLM)與發光二極體元件量測其特性與電性。Graphene is a two-dimensional carbon material which consists of hexagonal array of carbon atoms. It has great potential to use as transparent conductive electrodes in UVCLED because of its high electron mobility, thermal conductivity, Mechanical, and low sheet resistance. Most of all, it has great transmittance at 280 nm or lower wavelength light. Therefore, high specific contact resistance between graphene and GaN (especial p-GaN) is the biggest challenge that used graphene as transparent conductive electrodes in UVCLED. To decrease the specific contact resistance between graphene and GaN. In this study, we show two Buffer layers, including NiO and ITO dots to improve the adhesion and decrease the Schottky barrier. Our graphene is prepared by low pressure chemical vapor deposition, and p-GaN is provided by Epistar. One is deposit 2 nm NiO between graphene and p-GaN. The other way is add the etched ITO dots between graphene and p-GaN. Both experiments have annealed at 450℃in Ar ambient after add Buffer layer between graphene and GaN. And we used circular transmission line model (CTLM) and device tester to measure its characteristic and electrical resistance.