| 摘要(英) |
Despite years of research efforts, external quantum efficiencies of deep ultraviolet (DUV, wavelength ? 290 nm) LED remain below 20 %. This is because the P-type material of DUV LED requires high transmittance and high conductivity, which is not achievable with the commonly used material, i.e. AlGaN. Boron nitride (BN) has the characteristics of high energy bandgap (~ 6 eV) and low hole activation energy (~ 30 meV), preventing the absorption of DUV photons in the p-type contact layer, while providing sufficient free hole concentration for the operation of DUV LED. In addition, the high energy bandgap of BN effectively blocks the electron overflow from quantum wells. The abundant holes injected from BN increase the luminous efficiency of DUV LED and decrease the turn-on voltage, extending the life of device operation. All of these promising traits make BN an attractive p-type material for DUV LED.
To achieve high-quality BN, we grew the binary compound by metal-organic chemical vapor deposition (MOCVD). A 1.5-μm-thick aluminum nitride was firstly grown on the sapphire substrate. BN epitaxial layer was then attained with varied VIII ratios and carrier gas flow rates, with the attempt to improve crystal qualities. Finally, BN was doped with Mg2+ to accomplish p-type conductivity. Preliminary results suggest that the transmission and conductivity of p-type BN are significantly superior to those of p-type Al0.3Ga0.7N, exhibiting great potential for DUV LED applications. |
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