Research On The Characteristics Of Small Power Audio Static Induction Transistor

As the only semiconductor device with a characteristic of vacuum triode, static induction transistor (SIT) possesses many advantages, such as low source resistance, high switching speed, high voltage amplification factor, negative temperature coefficient, and has been widely used in acoustic frequency, high frequency and microwave fields, and has also been applied in power electrics devices.In this thesis, a SIT, which works in pre-amplification circuit, is designed and manufactured for small power acoustic equipment. The working mechanism of SIT is expounded systematically, especially the Ⅰ-Ⅴ characteristic, the channel potential barrier, and the theory of small current, moderate and large current cases. Simulation and theoretical analysis are conducted in order to get the optimal configuration and material parameter for excellent SIT characteristic. A detailed layout for positive photoresist technology and some key manufacturing processes, comparing with the former technology used in our institute, are presented in the thesis. After the manufacture, characteristics like the surface appearance, static characteristic, and dynamic characteristic are tested.1. The results show the chip has an desirable Ⅰ-Ⅴ characteristic, breakdown voltage of gate-source (G-S) is about-25V and gate-drain (G-D) is about-125V, leakage current of GS and G-D are40nA and70nA, respectively, Ⅰ-Ⅴ versus temperature shows no obviously variation, C-Vof G-S under the bias of-2V is about140pF and C-Ⅴ of GD under-25V is about20pF.2. Emphasizes are put on the breakdown voltage of G-S and G-D theory, and methods which cater for the current technology are proposed. The G-S breakdown voltage should be calculated as parallel plane punch-through junction, while G-D breakdown voltage should be seen as punch-through junction with curved edge, which is cylindrical. The G-D capacitance is mainly PN junction depletion capacitance. The G-S capacitance consists of PN junction depletion capacitance and capacitance between the metal and source, and those two parasitical capacitances are parallel relational.They are in accordance with the experimental data very well.3. By using the mode-conversion voltage, a method for calculating the lateral diffusion coefficient is proposed. The basic fine qualities of SIT are described, ie. large breakdown voltage, large transconductance,and large voltage amplification factor independent on the Gate-Source voltage fluctuates, which are crucial to identify the performance of a SIT, is excellent. The same analysis can be done on the transconductance with Gate-Source voltage.Comparisons are made between this work and2SK-79, a widely used audio device. The device we designed is an excellent surface gate SIT, and is suitable for the usage in the field of low-power audio applications, the overall design and manufacture technology have reached the international advanced level.