Influence of thermal stress on the relative permittivity of the AlGaN barrier layer in an AlGaN/GaN heterostructure Schottky contacts

doi:10.1088/1674-1056/20/9/097106

Abstract Ni Schottky contacts on AlGaN/GaN 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 AlGaN barrier layer was related to the piezoelectric and the spontaneous polarization of the AlGaN barrier layer. The relative permittivity was in proportion to the strain of the AlGaN barrier layer. The relative permittivity and the strain reduced with the increased thermal stress time until the AlGaN 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 stress 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 AlGaN 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 AlGaN/GaN heterostructure devices.

Keywords: AlGaN/GaN heterostructures relative permittivity of AlGaN barrier layer converse piezoelectric effect

Received: 23 December 2010
Revised: 28 March 2011
Accepted manuscript online:

PACS:	71.55.Eq	(III-V semiconductors)
	77.22.Ch	(Permittivity (dielectric function))
	77.22.Ej	(Polarization and depolarization)

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Lü Yuan-Jie(吕元杰), Lin Zhao-Jun(林兆军), Zhang Yu(张宇), Meng Ling-Guo(孟令国), Cao Zhi-Fang(曹芝芳), Luan Chong-Biao(栾崇彪), Chen Hong(陈弘), and Wang Zhan-Guo(王占国) Influence of thermal stress on the relative permittivity of the AlGaN barrier layer in an AlGaN/GaN heterostructure Schottky contacts 2011 Chin. Phys. B 20 097106

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Influence of thermal stress on the relative permittivity of the AlGaN barrier layer in an AlGaN/GaN heterostructure Schottky contacts

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