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

用等离子体激发氮气气源MBE在石英玻璃衬底上生长了多晶GaN层，发现其光致发光强度与用MOVPE在蓝宝石衬底上生长的单晶GaN一样强。同时实现了n型和p型掺杂，并提出了制造低成本和大面积光子器件的可能性。对于多晶GaN - pn结，证实了二极管特性。结果表明，多晶GaN的发光源是激子跃迁。我们在Mo， W， Ta和Nb金属衬底上生长了GaN，并观察到强烈的PL发射。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与金属之间功函数的差异。用氨源在玻璃和金属衬底上生长GaN层，获得了更强的PL发射。我们证实了GaN/金属pn结的二极管特性。这些结果显示了柔性GaN器件制造的可能性。我们还观察到在磁性氧化物LaSrMnO3衬底上生长的多晶GaN具有强发光，这表明了新型功能器件制造的可能性。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。期望应用于高性能显示设备。

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.