STUDY OF AlAs/GaAs ETCHING SELECTIVITY IN MESFET USING CITRIC ACID BASED SOLUTION
| Autor: | YANG, CHENG CHUNG, 楊正中 |
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| Rok vydání: | 1996 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 84 Three different type of solutions including C4H6O4/NH4OH/H2 O2,C6H8O7.H2O/ H2O2,C6H8O7/H2O2,were used as selective etching solutions for GaAs/AlAs,GaAs/ Al0.32Ga0.68As structure. The results of this study were applied to gate recess of the heterojunction MESFET. The DC characteristics of the MESFET using this selective etch were studied in this research. In this study,it is found that the C6H8O7.H2O/H2O2 solution with 7:1 ratio offers the highest selectivity for GaAs/AlAs layers, the selectivity is 600. The surface morphology of the AlAs after etched by C6H8O7.H2O/H2O2 was may smooth. The 7:1 C6 H8O7.H2O/H2O2 solution was applied to the gate recess of the MESFET with an etch stop layer of AlAs.The DC characteristics of the 1um MESFET with etch stop layer were measured. The maximum transconductance of the device was over 160mS/mm and the current density was about 376mA/mm. The average pinch-off voltage was -4.38V. The standard devition was measured for the whole wafer.It is found that the uniformity of MESFET with an etch stop layer was better than the MESFET without an etch stop layer. The experiment results indicate that the 7:1 C6H8O7/ H2O/H2O2 solution is ideal for selective etch of GaAs/AlAs layer.The MESFET that has an etch stop layer of AlAs for gate recess gives better uniformity after selective etching. From the DC characteristics,we also find that the existence of the AlAs layer does not reduce the performance of the MESFET device. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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