| Semi-insulating Gallium Arsenic (SI-GaAs) is a kind of semiconductor withsemi-insulating properties, higher mobility， direct and wide band-gap. Thesemiconductor devices made by gallium arsenide have the characteristics ofthermostable, low noise, high speed, high frequency, higher radiation hardness etc,and is an exensive application in high-tech field such as communication device, nightvision technology and detector. With the progress of nuclear and space technology,demand is increasing for the semiconductor devices used in the radiation environment.In current commercial SI-GaAs crystal growth process, Liquid EncapsulatedCzochralski (LEC) method and Vertival Gradient Freeze (VGF) method are majortechnology. Therefore, the investigation on radiation characteristics of LEC and VGFSI-GaAs is of great application value.In this paper, we mainly focus on the structural and electrical properties in largediameter LEC and VGF SI-GaAs after electron irradiation. The patterns of defectswere investigated by means of ultrasonic AB etching, metallurgical microscope andinfared technique in as-grown LEC and VGF SI-GaAs, and different patterns ofdislocations and micro-defects were observed. The concentration and radialdistribution of EL2defect and impurity C are characterized by Fourier transforminfrared spectroscopy (FTIR). The structure properties induced by electron irradiationwere studied by Raman spectra. And the influence of irradiation and annealing on theelectrical properties of materials is studied by Hall Testing System.There are different experimental results in the LEC and VGF SI-GaAs samples.The cellular and netted dislocations distribution is visible in the LEC SI-GaAssamples and the isolated or a few intersected dislocations are a major featrue in theVGF SI-GaAs samples after ultrasonic AB etching. The concentration of EL2defectand impurity C is almost equal in the two samples, but their radial distribution isdifferent. The Raman spectra of two SI-GaAs samples show that the disorder degreeis increased and the nature of defect is changed after electron irradiation. Themagnitude and the number of defect peak added in electron-irradiated LEC SI-GaAssamples. As to the VGF SI-GaAs samples, the defect peaks position shifted in thesamples irradiated by lower energy and the number of defect peaks decreased in thesamples irradiated by higher energy. The carrier concentration and the Hall mobility decreased and the resistivity increased after electron irradiation. The mobility becamebetter in LEC sample irradiated by lower fluenceIn. In LEC and VGF samplesirradiated by higher energy, electrical parameters did not have markly change atdifferent annealing temperature until800℃. After annealing at800℃theconductivity type is changed from n-type to p-type, the carrier concentration sharplyincreased, the resistivity and mobility decreased in irradiated samples, which are dueto the evaporation of As in surface of samples and the out-diffusion of As interstitialin interior of samples. |
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