| Abstract: | A.Design and Analysis of a 90V Microwave P-I-N Diode Switches
A PIN diode is very similar to a PN diode (a pn junction), except that an intrinsic layer1, sometimes referred to as the bulk of the diode, is placed in between the p and n type materials. PIN diodes are more commonly used in photo detectors than PN diodes since the intrinsic region presents a larger volume in which photons can produce electron-hole pairs and so the thickness of this region can be adapted to increase quantum efficiency. The thickness of this region also gives them a lower capacitance than a typical PN diode. With a forward bias, the PIN diode behaves like a variable resistor for high-frequency signals. With a reverse bias, it acts as a parallel plate capacitor [53]. The most commonly used materials in PIN diodes are Silicon (Si) and Gallium Arsenide (GaAs). Since the focus of this thesis is on Si PIN photodiodes. The bulk region of Si PIN detectors is ideally composed of a very high resistivity (ρ) intrinsic silicon. However, in practice this region is doped with slightly n-type, n − silicon, or slightly p-type, p− silicon.
B.Design of High performance UMOSFETs for power switching Application
POWER MOSFET’s with the inherent advantages of fast switching response, excellent thermal stability and high input impedance have recently begun to displace power bipolar transistors in high-frequency switching applications. One important concern related to power MOSFET’s is the reduction of the specific on-resistance. VDMOSFET’s (vertical double-diffused MOSFET’s) are now widely used as power MOSFET’s. The specific on-resistance of VDMOSFET’s has been steadily decreased by reducing the cell pitch. However, further reductions in the specific on-resistance have been hampered by a parasitic JFET, i.e., excessive reduction in the cell pitch increases the specific on-resistance [4]. Thus there is an optimum cell pitch that gives the lowest specific on-resistance. UMOSFET’s (U-grooved MOSFET’s) having a vertical trench gate structure have been proposed in an attempt to solve the problem of the parasitic JFET. For 100-V UMOSFET’s, the specific on-resistance can be significantly decreased by reducing the cell pitch [4]. Some self-aligned technologies for reducing the cell pitch have been reported. In this, we introduced a trench contact UMOSFET The integration of high voltage power transistors with control circuitry to form smart Power Integrated Circuits (PIC) has numerous applications in the areas of industrial and consumer electronics. These smart PICs must rely on the availability of high performance power transistors. In this thesis, a vertical U-shaped gate MOSFET (UMOS) are proposed The proposed new process and structure offers superior performance, such as low on-resistance, high breakdown voltage. A specific on-resistance Ron = 1.1mΩ·cm2 is observed, which is 45% better than that of the other UMOS structure. The improvement in the device’s Figure-of-Merit (FOM = Ron × Qg) is about 58%. |
