Crystal growth of AlInGaNAs 5-alloy nitrides and fundamental investigation for fabricating optoelectronic integration circuit

在这一年中，我们开始了包括In原子的2-，3-和4-合金氮化物的晶体生长的基础研究，如InN/Si，InAs/Si和InGaNAs/Si，然后实际进行5-合金氮化物的晶体生长，如AlInGaNAs异质外延层在Si衬底上具有更高的结晶质量。因为作为源的In金属的高蒸发，所以在高温下包含In原子的合金氮化物的晶体生长是困难的。随着In含量的增加，合金膜的结晶质量明显下降。此外，即使是简单的InN薄膜在8.5K下也不发射带边PL发射。在对5-合金氮化物晶体生长的研究进行调查之前，我们决定首先解决这些问题。因此，我们研究了用电子回旋分子束外延在Si衬底上生长InN薄膜的最佳生长条件。我们发现，在500 ℃、10 nm厚的InN缓冲层上、250 ℃生长温度下、氮等离子体发射强度为357 nm的2倍、391 nm发射强度最弱的条件下生长InN薄膜，是获得最高结晶质量的六方InN薄膜的最佳生长条件。此外，生长前的衬底氮化促进了六方InN晶体的生长，显着提高了晶体质量。除非衬底氮化，否则薄膜的质量明显下降，变成非晶态。此外，我们使用红外光成像炉在高温下退火样品，并尝试改善结晶质量。结果表明，随着退火温度的提高，晶体质量得到了很大的改善。然而，高于550 ℃的退火使薄膜的表面形貌突然退化，这可能是由于N原子从InN薄膜表面的再蒸发。

In this year, we started fundamental research on crystal growth of 2-, 3- and 4-alloy nitrides including In atom such as InN/Si, InAs/Si and InGaNAs/Si before actually proceeding crystal growth of 5-alloy nitrides such as AlInGaNAs heteroepitaxial layers with higher crystalline quality on Si substrates. Because crystal growth of alloy nitrides including In atom at high temperature is difficult because of high evaporation of In metal as a source. With increasing the content of In atoms in alloy films, it was evident that the crystalline qualities of alloy films would be much degraded. Moreover, even simple InN films did not emit the band-edge PL emission at 8.5 K. Before investigating the research on crystal growth of 5-alloy nitrides, we decided to solve these problems in the first place. Therefore, we investigated the optimum growth conditions of InN films grown on Si substrates by electron cyclotron molecular beam epitaxy. We found the optimum growth conditions that InN film grown at 500 ℃ on the 10 nm-thick InN buffer layer at a growth temperature of 250 ℃ and under nitrogen plasma with twice of the usual 357 nm-plasma emission and the weakest 391 nm-plasma emission intensities is essential to obtain hexagonal-InN with the highest crystalline quality. Moreover, the substrate nitridation before growth promoted crystal growth of hexagonal-InN and dramatically improved crystalline quality. Unless the substrate nitridation, it is evident that the quality of the films would be degraded and become amorphous. Moreover, we annealed the samples at high temperatures using infrared light imaging furnace and tried the improvement of crystalline quality. As a result, the crystalline quality was much improved with increasing the anneal temperature. However, anneals higher than 550 ℃ abruptly degraded the surface morphologies of the films probably because of re-evaporation of N atoms from the surfaces of InN films.