载气流量对HVPE外延生长GaN膜光学性质的影响

研究了利用水平氢化物气相外延 (HVPE)系统在蓝宝石衬底上外延氮化镓 (Ga N)的生长规律 ,重点研究了作为载气的氮气流量对 Ga N膜的结构及光学性质的影响。观察到载气流量对预反应的强弱有很大影响 ,外延膜的质量和生长速度对载气流量极为敏感。当载气流量较小时 ,样品的 X射线衍射谱 (XRD)中出现了杂峰(1 0 -1 1 )和 (1 1 -2 0 ) ,相应的光致发光谱 (PL)中出现了黄带 (YL) ,靠近带边有杂质态。而当载气流量增大时 ,样品质量改善。Ga N外延膜的结构和光学性质的相关性表明深能级的黄带与生长过程中产生的非 c轴方向晶面有关 ,据此我们推测 :Ga空位与束缚在 (1 0 -1 1 )和 (1 1 -2 0 )等原子面上的杂质构成复合结构 ,这些复合结构所产生的深能级对黄带的发射有贡献 ;由于预反应使生长过程中混入的附加产物及杂质对带边发射有重要影响

Influence of Carrier Gas Flow Rate on the Optical Properties of GaN Films Grown by HVPE

The influence of carrier gas (i.e. N 2) flow rate on the optical properties of GaN epilayers on sapphire substrates grown by horizontal halide vapor phase epitaxy (HVPE) system was studied. It has been found that carrier gas flow rate produces a significant effect on both pre reactions and the quality of the films. Both (10 11) and (11 20) peaks of the X ray diffraction (XRD) spectra and the relevant yellow luminescence (YL) of the photoluminescence (PL) spectrum as well as the impurity states close to the band edge were respectively observed upon lowing the N 2 flow rate. The quality of the samples was improved with increasing carrier gas flow rate. The correlation of structural and optical properties of the GaN films manifested a close relation of deep level yellow luminescence to non c planes developed during the growth. It was speculated that the emission of YL is probably due to the formation of deep gap state in the band gap resulting from the complex of Ga vacancy and impurities trapped at (10 11) and (11 20) atomic facets.