Shiou-Ying Cheng et al 2004 Semicond. Sci. Technol. 19 351 doi:10.1088/0268-1242/19/3/010
Shiou-Ying Cheng1, Jing-Yuh Chen2, Chun-Yuan Chen2, Hung-Ming Chuang2, Chih-Hung Yen2, Kuan-Ming Lee2 and Wen-Chau Liu2
Show affiliationsThe performances of InGaP/AlxGa1−xAs/GaAs heterojunction bipolar transistors (HBTs) with different doping concentrations of AlxGa1−xAs graded layers are theoretically studied. The use of the AlxGa1−xAs graded layer plays a key role in affecting the direct current and radio frequency performances of the studied HBTs. It is found that the studied devices with suitable doping concentrations of AlxGa1−xAs graded layers exhibit lower offset voltages, saturation voltages, and base and collector current ideality factors. Furthermore, due to the use of proper doping concentrations of AlxGa1−xAs graded layers, the studied devices show high values of the unity current gain cut-off frequency (fT) and maximum oscillation frequency (fmax). It is known that, from the theoretical analysis, the appropriate doping concentration of the AlxGa1−xAs graded layer is 1 × 1016 to 1 × 1018 cm−3. Consequently, this work is promising for device engineers to design high-performance HBT structures.
85.30.De Semiconductor-device characterization, design, and modeling
85.40.Ry Impurity doping, diffusion and ion implantation technology
Issue 3 (March 2004)
Received 11 March 2003, in final form 5 November 2003
Published 23 December 2003
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