Influence Of Defects In Substrate Material Of LEC SI-GaAs On The Electrical Performance Of Mesfet Devices

GaAs crystal is a kind of III-V group compound semiconductor material with good electrical performance.The semiconductor devices and integrated circuit (IC) fabricated on GaAs substrate have such advantages of hign-speed information processing that they have drawn the researcher's attention . Especially, MESFET devices fabricated on LEC SI-GaAs substrate have been adopted into very large-scale integration(VLSI) and monolithic microwave integrated circuit(MMIC) extensively. Therefore, it is necessary to study the influence of defects in substrate material of LEC SI-GaAs on performance of MESFET to meet the need of design and fabrication of GaAs IC.As recent research and productive practice showed, such conventional parameters as dislocation densiry(EPD),charge carrier concentration,mobility were not enough to evaluate the SI-GaAs material's quality , let alone revealing the relationship between the quality of material and the performance of devices.On the other hand, recent research showed that AB microdefects had direct relationship with device performance , whose density (AB-EPD) was more important than EPD for revealing the relationship between the quality of material and the performance of devices .This dessertation systematically researched dislocation and AB microdefects etched by molten KOH and by AB etching respectively in GaAs substrate, which were provided by merchants from home and overseas, as well as their influence on electrical parameters. In addition, we fabricated MESFET devices on LEC SI-GaAs substrate and studied the relationship between these parameters and MESFET devices performance such as gm, saturated drain current and threshold voltage . At last, we tried to explain the reason of the above relationship.On the other hand,we proved the relationship between AB microdefects and MESFET devices performance via PL mapping method.The experimental results showed that firstly, the distribution of resistiveity, mobility, Carrier concentration , EPD and AB-EPD in GaAs substrate was not uniform; secondly, the distribution of electrical parameters depended on that of EPD and AB-EPD ; thirdly, MESFET devices performance correlated with AB microdefects;last,as shown by PL mapping results, it is substrate with better parameters quality that could provide more chance to fabricate good MESFET devices.