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[摘要]：Great improvement in crystal quality of a-plane (non-polar) GaN has been achieved using a simple but effective overgrowth technique based on self-organized nano-masks. This has been confirmed by a massive reduction in full width at half maximum of x-ray diffraction rocking curves measured along both symmetrical and asymmetrical directions. Taking the advantage of utilising the nano-masks, a quick coalescence with a thickness of less than 1 mu m has been obtained, which is much less than that using any conventional overgrowth techniques. The dislocation density has been significantly reduced by more than one order magnitude compared with a standard a-plane GaN layer on sapphire. An InGaN/GaN multiple quantum well (MQW) structure grown on the high quality a-plane GaN has demonstrated an enhancement with a factor of 7 in optical efficiency, compared with a similar MQW structure grown on a standard c-plane GaN layer. The excitation-power dependent photoluminescence measurements have confirmed that the a-plane InGaN/GaN MQW structure does not suffer from quantum-confined Stark effect any more. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3658803] |
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