Ni Schottky contacts on A1GaN/CaN heterostructures were fabricated. Some samples were thermally treated in a furnace with N2 ambience at 600 ~C for different times （0.5 h, 4.5 h, 10.5 h, 18 h, 33 h, 48 h, and 72 h）,...Ni Schottky contacts on A1GaN/CaN heterostructures were fabricated. Some samples were thermally treated in a furnace with N2 ambience at 600 ~C for different times （0.5 h, 4.5 h, 10.5 h, 18 h, 33 h, 48 h, and 72 h）, the others were thermally treated for 0.5 h at different temperatures （500 ~C, 600 ~C, 700 ~C, and 800 ~C）. With the measured current-voltage （I-V） and capacitance-voltage （C V） curves and by self-consistently solving Schrodinger＇s and Poisson＇s equations, we found that the relative permittivity of the A1GaN barrier layer was related to the piezoelectric and the spontaneous polarization of the A1GaN barrier layer. The relative permittivity was in proportion to the strain of the A1GaN barrier layer. The relative permittivity and the strain reduced with the increased thermal stress time until the A1GaN barrier totally relaxed （after 18 h at 600 ~C in the current study）, and then the relative permittivity was almost a constant with the increased thermal strcss time. When the sample was treated at 800 ~C for 0.5 h, the relative permittivity was less than the constant due to the huge diffusion of the contact metal atoms. Considering the relation between the relative permittivity of the A1GaN barrier layer and the converse piezoelectric effect, the conclusion can be made that a moderate thermal stress can restrain the converse piezoelectric effect and can improve the stability of A1GaN/GaN heterostructure devices.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.10774090)the National Basic Research Program of China (Grant No.2007CB936602)
文摘Ni Schottky contacts on A1GaN/CaN heterostructures were fabricated. Some samples were thermally treated in a furnace with N2 ambience at 600 ~C for different times （0.5 h, 4.5 h, 10.5 h, 18 h, 33 h, 48 h, and 72 h）, the others were thermally treated for 0.5 h at different temperatures （500 ~C, 600 ~C, 700 ~C, and 800 ~C）. With the measured current-voltage （I-V） and capacitance-voltage （C V） curves and by self-consistently solving Schrodinger＇s and Poisson＇s equations, we found that the relative permittivity of the A1GaN barrier layer was related to the piezoelectric and the spontaneous polarization of the A1GaN barrier layer. The relative permittivity was in proportion to the strain of the A1GaN barrier layer. The relative permittivity and the strain reduced with the increased thermal stress time until the A1GaN barrier totally relaxed （after 18 h at 600 ~C in the current study）, and then the relative permittivity was almost a constant with the increased thermal strcss time. When the sample was treated at 800 ~C for 0.5 h, the relative permittivity was less than the constant due to the huge diffusion of the contact metal atoms. Considering the relation between the relative permittivity of the A1GaN barrier layer and the converse piezoelectric effect, the conclusion can be made that a moderate thermal stress can restrain the converse piezoelectric effect and can improve the stability of A1GaN/GaN heterostructure devices.
