氮化鋁鎵(AlGaN)是深紫外光發光二極體[deep ultraviolet light emitting diode (DUV -LED), 波長<290 nm ]最常使用的材料。然而，含有氮化鋁鎵的DUV LED，儘管經過十多年的研究開發，其外部量子效應(external quantum efficiency, EQE)始終難以超越10%。這歸咎於p 型AlxGaN1-x的活化能(active energy)非常高(170 – 510 meV)，導致電洞注入效率不高，因此p-AlxGaN1-x的導電率很低。我們使用了氮化硼(boron nitride, BN)來取代氮化鋁鎵(AlGaN)，BN的電洞活化能遠低於AlGaN，還有很高的化學穩定性和熱穩定性，這些都是DUV -LED需要的特質。為了評估p 型BN(p-BN)的電性，我們以霍爾量測(Hall measurement)分析不同的金屬電極、退火條件以及不同磊晶條件的p-BN，希望能以p-BN形成歐姆接觸(ohmic contact)。我們發現，在p-BN表面加上一層厚度約3-nm的InGaN接觸層，或降低BN磊晶的五三比，能有效降低p-BN的接觸電阻。;Aluminum gallium nitride (AlGaN) is the most commonly used material for deep ultraviolet light emitting-diodes (DUV LEDs, emission wavelength < 290 nm). However, the external quantum efficiencies (EQEs) of DUV LEDs rarely reach 10 %, despite years of research efforts. The main reason is the extremely high activation energies of conventional acceptors in p-type AlxGa1-xN (170 – 510 meV). This intrinsic drawback subsequently results in low hole injection efficiency, and accordingly the conductivity of p-AlxGa1-xN. To overcome the difficulty, we employ boron nitride (BN) as the alternative to p-type AlGaN. BN is reported to exhibit much lower acceptor activation energy than AlGaN, in addition to her high chemical and thermal stability. These are attractive merits for the applications in DUV LEDs. To evaluate the electrical properties of p-type BN (p-BN), we systematically characterized p-BN with Hall measurements using different metal electrodes, annealing conditions, growth pressure, and V/III ratios with the intention to achieve ohmic contact on the two-dimensional layer. It is found that adding a 3-nm InGaN contact layer on the surface, or reducing the V/III ratio, can effectively reduce the contact resistance of p-BN.
