Study On The Dislocation Characteristics Of GaAs/Si And InP/GaAs Metamorphic Wafers

InP/GaAs and GaAs/Si can realize the integration of different system materials by means of large mismatch metamorphic growth, and promote the development of the optoelectronic integrated (OEIC) technology. InP has the advantages of excellent photoelectric properties, and GaAs has the advantages of mature development, high size and low price. The compatible heterogeneous integration of InP and GaAs can overcome the defects of InP materials with high price and poor mechanical strength quality. The integration of GaAs and Si can make full use of the excellent properties of the Si substrate with big size, low cost and highly mature integration. However, InP/GaAs with3.8%lattice mismatch and GaAs/Si with4.1%lattice mismatch lead to the high etching pit density, and seriously affect the crystalline quality of the metamorphic material. Therefore, a quick, clear and accurate dislocation characterization technique is needed to assess the etching pit density of the metamorphic material, and then it used to optimize the metamorphic growth process. Now there are some dislocation characterization techniques, such as transmission electron microscope method (TEM). wet chemical etching method, X-ray diffraction method and photoluminescence method. TEM and wet chemical etching method both belong to direct dislocation characterization techniques. But compared with the defects of TEM with difficult sample preparation, high price and waste time, wet chemical etching method with low cost, simple operation has attracted much attention.In this thesis, the etching pit morphologys in InP and GaAs substrates were acquired by wet chemical etching method. The etching pit acquired by wet chemical etching method was served as the dislocation characterization of InP/GaAs and GaAs/Si metamorphic wafers. The main research work and achievement of this thesis are listed below:1. The HB1(content was more than40%) solution and Huber (HBr:H3PO4=1:2)solution were used to etch the InP (100) substrate produced by AXT company. The best etching conditions of the InP substrate were listed below:the etching solution is HBr solution, the etching temperature was19℃, the etching time was120s, the etching depth is7.2μm, continuous stirring with glass rod was implemented during the etching process. The etching results observed by the optical microscope with200times amplification were that the etching pit morphology is the square cone pit, the average etching pit density is about2×102/cm2.2. The etching rates of HBr solution, different dilution ratio (HBr:H2O=3:1and HBr:H2O=5:1) solution and Huber solution were measured separately. The four solutions were used to etch InP metamorphic crystal with1.16μm thickness growed on GaAs(100) substrate. The best etching conditions of the InP/GaAs metamorphic wafer were listed below:The oxide layer of the InP/GaAs metamorphic wafer was removed by dilute hydrochloric acid before the etching experiment. The etching solution is Huber solution, the etching temperature was19℃, the etching time was90s, the etching depth is600nm, continuous stirring with glass rod was implemented during the etching process. The etching results observed by the scanning electron microscope were that the etching pit morphology is the polygon pit, the etching pit sizes range from500nm to2000nm in diameter and the average etching pit density is about108/cm2magnitude.3. The molten analytical reagent KOH was served as the etching solution of the GaAs (100) substrate. The etching results of GaAs substrate were listed below:the etching pit morphology is the hexagon cone pit, the average etching pit density is about7×102/cm2.4. The etching rate of the molten KOH was measured, and the rate was used to etch GaAs metamorphic crystal with1.93μm thickness growed on Si(100) substrate. The best etching conditions of the GaAs/Si metamorphic wafer were listed below:the etching temperature was330℃, the etching time was180s, the etching depth is300nm. The etching results observed by the scanning electron microscope were that the etching pit morphology is the sunken pit, the etching pit sizes range from150nm to650nm in diameter and the average etching pit density is about108／cm2magnitude.