The performances of second harmonic gen eration (SHG) and optical parametric oscillator (OPO) in CdGeAs2 crystal are strongly influenced by surface quality. In this paper, the surfaces of samples were treated by mechanical polishing (MP), chemical polishing (CP), chemical-mechanical polishing (CMP) and CP following CMP closely (CMP + CP). Then, the surface state was characterized by optical microscopy (OM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM measurements show that an ultra-smooth surface is achieved after CMP + CP treatment and the roughness value is 0.98 nm. Meanwhile, the roughness of the surfaces treated by MP, CP and CMP are 4.53, 2.83 and 1.38 nm, respectively. By XRD rocking curves, the diffraction peak which belongs to the wafer treated by CMP + CP is the highest in intensity and best symmetrical in shape. XPS analysis indicates that Ge4+ proportions of GeO2 in total Ge content of CdGeAs2 wafers' surface after MP, CP, CMP and CMP + CP treatment are 27.6%, 42.8%, 6.1% and 30.3%, respectively.
Wei HuangBei-Jun ZhaoShi-Fu ZhuZhi-Yu HeBao-Jun ChenZhen ZhenYun-Xiao Pu
采用改进的布里奇曼法生长出尺寸为Φ15 mm×45 mm,外观完整无开裂的Cd Ge As2单晶体。为了提高器件的使用性能,需要对晶体进行表面处理,主要对Cd Ge As2晶片表面的抛光技术进行了研究。通过对解理面切割分析得到(101)晶面,机械抛光后进行了XPS分析。对该晶面采用溴甲醇溶液进行腐蚀抛光,采用XRD回摆及光学显微镜对不同抛光时间的试样进行观测。结果表明,CGA晶体的(101)晶面在常温下采用溴甲醇溶液腐蚀50 s后,晶片表面光滑无划痕,并且具有半峰宽较小的回摆曲线,同时计算得到Cd Ge As2晶体的表面损伤层厚度。
A high-quality ZnGeP_(2)(ZGP)single crystal with large size ofΦ30 mm×80 mm was grown by a modified vertical Bridgman method.ZGP wafers were annealed with ZGP polycrystalline powder for 300 h at 550,600 and 650℃,respectively.The as-grown and annealed crystals were characterized by X-ray diffraction(XRD)analysis,Fourier transform infrared spectroscopy(FTIR),IR microscope and energy-dispersive spectroscopy(EDS).Results show that the quality of all wafers is improved evidently after annealing and the optimum annealing temperature obtained is 600℃.The IR transmittance of the wafer measured by FTIR is up to 56.78%at wavelength of 2.0μm nearby and exceeds 59.00%in the wavelength range of 3.0-8.0μm.The deviations from stoichiometry decrease,and the homogeneity of the crystal is also improved after annealing.In this paper,scanning infrared map was proposed as a new nondestructive method to evaluate optical quality and homogeneity of crystal through comparing the IR transmittance with the three-dimensional IR spectral contour map.
