Study on Polycrystalline Photonics, by Using III-V Nitrides Grown on Amorphous and Polycrystalline Substrates

用气体源分子束外延技术在石英玻璃衬底上生长了GaN多晶薄膜，发现其光致发光强度与用MOVPE方法生长在蓝宝石衬底上的单晶GaN一样强。同时实现了n型和p型掺杂，为制备低成本、大面积的光子器件提供了可能性。对于多晶GaN pn结，证实了二极管的特性。研究发现，多晶GaN的发光来源于激子跃迁。我们在Mo、W、Ta和Nb金属衬底上生长了GaN，观察到了很强的发光。结果表明，多晶GaN/金属结具有肖特基或欧姆特性，这取决于GaN和金属功函数的不同。用氨源在玻璃和金属衬底上生长GaN层，可以得到更强的发光。我们确认了GaN/金属pn结的二极管特性。这些结果表明了制作柔性GaN器件的可能性。我们还观察到了生长在磁性氧化物LaSrMnO_3衬底上的多晶GaN的强烈发光，这表明了制作新型功能器件的可能性。我们还观察到金属衬底上的多晶GaN具有良好的电场电子发射性能。高性能显示设备的应用是可望的。

Polycrystalline GaN layers were grown on quartz glass substrates by gas source MBE with plasma-excited N2, and it was found that the photoluminescence (PL) emission was as strong as those of single crystalline GaN grown on sapphire substrates by MOVPE. Both n- and p-type doping was achieved and we suggested the possibility of the fabrication of low cost and large area photonic devices. For the polycrystalline GaN pn junctions, the diode characteristics were confirmed. It was found that the origin of the PL emission from the polycrystalline GaN is excitonic transition. We have grown GaN on Mo, W, Ta and Nb metal substrates and observed strong PL emission. It was found that the polycrystalline GaN/metal junctions showed Schottky or ohmic characteristics depending on the difference in the work-function between GaN and metals. By growing GaN layers on glass and metal substrates with ammonia source, much more strong PL emission was obtained. We confirmed the diode characteristics for the GaN/metal pn junctions. These results show the possibility of the fabrication of flexible GaN devices. We also observed strong PL from the polycrystalline GaN grown on magnetic oxide LaSrMnO3 substrates, which shows the possibility of novel functional device fabrications. We also observed good electric-field electron-emission properties for the polycrystalline GaN on metal substrates. Applications to the high performance display devices are expected.