High quality GaN films on (0001) sapphire substrates were grown by a commercial MOCVD system (Thomas Swan Corp.).The etch pits and threading dislocations(TDs) in GaN films have been studied by chemical etching methods such as mixed acid solution (H 3PO 4∶H 2SO 4=1∶3) and molten KOH,HCl vapor etching method,scanning electron microscope (SEM) and transmission electron microscope(TEM).SEM images of the same position of GaN films with HCl vapor etching and wet etching methods show notably different densities and shapes of etching pits.The results indicate that HCl vapor etching can show pure edge,pure screw and mixed TDs,mixed acid solution can show pure screw and mixed TDs and molten KOH wet etching only can show pure screw TDs.
Waveguide characteristics of symmetrical separate confinement heterojunction multi quantum well (SCH MQW) AlGaN/GaN/InGaN laser diode (LD) are studied by using one dimensional (1 D) transfer matrix waveguide approach.Aiming at photon confinement factor,threshold current,and power efficiency,layers design for SCH MQW LD is optimized.The optimal layers parameters are 3 periods In 0.02 Ga 0.98 N/In 0.15 Ga 0.85 N QW for active layer,In 0.1 Ga 0 9 N for waveguide layer with 90nm thick,and 120×(2 5nm/2 5nm) Al 0.25 Ga 0 75 N/GaN supper lattices for cladding layer with the laser wavelength of 396 6nm.
利用 X射线衍射 (XRD)测量用 MOCVD生长的 In Ga N样品 ,观察到 In N相 .通过 X射线衍射理论 ,计算得到 In N相在 In Ga N中的含量 .通过退火和变化生长条件发现 In N相在 In Ga N薄膜中的含量与生长时 N2 载气流量、反应室压力和薄膜中存在的应力有关 .进一步的分析表明 In Ga N合金中出现 In N相的主要原因是相分离 .
