Waltereit P, Brandt O, Trampert A, Grahn HT, Menniger J, Ramsteiner M, Reiche M, Ploog KH
Paul-Drude-Institut fur Festkorperelektronik, Berlin, Germany.
Nature. 2000 Aug 24;406(6798):865-8. doi: 10.1038/35022529.
Compact solid-state lamps based on light-emitting diodes (LEDs) are of current technological interest as an alternative to conventional light bulbs. The brightest LEDs available so far emit red light and exhibit higher luminous efficiency than fluorescent lamps. If this luminous efficiency could be transferred to white LEDs, power consumption would be dramatically reduced, with great economic and ecological consequences. But the luminous efficiency of existing white LEDs is still very low, owing to the presence of electrostatic fields within the active layers. These fields are generated by the spontaneous and piezoelectric polarization along the [0001] axis of hexagonal group-III nitrides--the commonly used materials for light generation. Unfortunately, as this crystallographic orientation corresponds to the natural growth direction of these materials deposited on currently available substrates. Here we demonstrate that the epitaxial growth of GaN/(Al,Ga)N on tetragonal LiAlO2 in a non-polar direction allows the fabrication of structures free of electrostatic fields, resulting in an improved quantum efficiency. We expect that this approach will pave the way towards highly efficient white LEDs.
基于发光二极管（LED）的紧凑型固态灯作为传统灯泡的替代品，目前在技术上备受关注。迄今为止，最亮的LED发出红光，并且比荧光灯具有更高的发光效率。如果这种发光效率能够转移到白色LED上，那么功耗将大幅降低，从而产生巨大的经济和生态效益。但是，由于有源层中存在静电场，现有白色LED的发光效率仍然很低。这些电场是由沿六方III族氮化物（用于发光的常用材料）的[0001]轴的自发极化和压电极化产生的。不幸的是，这种晶体取向对应于沉积在现有衬底上的这些材料的自然生长方向。在这里，我们证明在四方LiAlO2上以非极性方向外延生长GaN/(Al,Ga)N可以制造出无静电场的结构，从而提高量子效率。我们预计这种方法将为高效白色LED铺平道路。
