坩埚下降法生长红外砷化镓晶体的研究

Growth of Infrared GaAs Crystal by Vertical Bridgman Method

利用坩埚下降法生长红外砷化镓晶体,坩埚下降炉控温1 260℃,晶体以2.5mm/h速度在温度梯度为10℃/cm的条件下结晶生长.PBN坩埚外壁黏附有气相自发成核、尺寸为1~3mm的砷化镓单晶颗粒.生长的砷化镓晶体直径约50.8mm,总长约140mm.晶体头部放肩阶段存在异相成核,尾部出现多晶.截断后获得的砷化镓单晶长约100mm,成晶率达70%.砷化镓单晶结晶质量良好,头尾平均位错密度分别为868cm-2和1 436cm-2,电阻率达107Ω·cm量级.砷化镓单晶整体红外透过率约为55%,接近最高理论透过率55.8%.满足工业界使用要求.

The growth of infrared GaAs crystal is studied via the vertical Bridgman method. The pulling down furnace temperature is controlled at 1 260 ℃. GaAs crystal is grown at a rate of 2.5 mm/h under 10 ℃/cm temperature gradient. Some spontaneously nucleated GaAs single crystal particles with 1-3 mm size are found attach on the outside wall of PBN crucible. The grown GaAs crystal is about 50.8 mm in diameter and about 140 mm in length. A heterogeneous nucleation is formed in the head of the crystal and some polycrystal is taken place in the tail part. The cut GaAs single crystal is about 100 mm in length and the overall crystalline rate is up to 70%. The obtained GaAs single crystal has excellent crystallization quality. The average etching pits density of the head and tail parts of the crystal is 868 cm- 2 and 1 436 cm -2, respectively. The resistivity of the crystal is tested on the level of 10^7 Ω· cm. The infrared transmittance of the whole GaAs crystal is about 55% （nearly reaches the highest theory value 55.8%）, which can meet the requirements for industry application.