The Identify Of Microdefects In Semi-insulating Gallium Arsenide

Gallium Arsenide(GaAs) is important compound semiconductor material. It has high electron transfer rate and direct transition energy band structure. GaAs is fit to be made into high frequency, high speed ,endure heat ,anti- radiation and luminescence apparatus. These apparatus' capability are direct affected by the quality of GaAs substrate. In the production of GaAs single crystal only dislocation density was used to describe the structure parameter. Practice indicate that the only one parameter can't token the quality of semi-insulating Gallium Arsenide (SI-GaAs) single crystal.One can not make sure that the good material selected can be made into good apparatus.The microdefects in GaAs single crystal can also have important effect on the apparatus.Although in recent years the study on microdefects in GaAs has been carried through by the scientists home and abroad, the study usually just on one aspect and there is conflict in the definition of microdefects and the explanations on it's essential.The aim of this task is to open out the essential of the microdefects in GaAs , to investigate the distributing order on the wafer,and the interaction between microdefect and dislocation ,and also to study microdefects' influence on apparatus capability. Because there is a strong interaction between microdefects and dislocations,the study on them must been made simultaneously.Firstly, we used the Ultrasonic-aided Abrahams-Buiocchi etching(USAB) to reveal the design of defects in SI-GaAs.Then through the metalloscope and transmission electron microscope(TEM),X-rays transmission topography and PL mapping and so on we analysed the design and found out the origin of these designs.Based on the literature and experiments, we found that the microdefects in SI-GaAs are the result of agglomeration of point defects. They consist in GaAs as microprecipitate, small dislocation loop or the complex of impurity and as-grown point defects. The size of microdefects is in micron rank. The distribution of microdefects on two inch and three inch wafers is different. Most of them decorate on dislocations for absorption, fewness lie in denudation which is apart from dislocations about twenty micronfor the absorption of dislocations is very weak. At the same time, Ultrasonic-aided Abrahams-Buiocchi etching(USAB) can also reveal mechanism damnification on wafer surface. Ultrasonic-aided Abrahams-Buiocchi etching(USAB) also has memory effect on the reveal of defect,so the pit revealed is not the defect on the origin suface but the trace of the defect after 20 micron has been etched.Microdefect can affect the threshold voltage and the thress compression of the MESFET.There is a critical value on microdefect density.The thress compression will increase suddenly when the density is smaller than the value.The exact understand on the essential of microdefect can guide the pruduce of material and the process of apparatus.