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Novel High Speed Devices and Heterostructures Prepared by Molecular Beam Epitaxy

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Letter rept. for period ending FY90, 1 Oct 1989-30 Sep 1990,

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The research funded the following projects - Metal-Insulator- Semiconductor Field-Effect-TransistorMISFET, GeGaAs Heterojunction Bipolar Transistor HBT, power HBT, and a theoretical investigation on Direct and Resonant Tunneling Diode RTD. This project investigated the properties of MISFET type structures based on compound semiconductors. MISFETs have advantages over the aforementioned transistors in areas where high speed, simplicity of fabrication, uniformity of threshold voltages, low standby power, and high gate operational voltages are required. A major research goal is to investigate GeGaAs heterojunctions towards incorporating Ge in well established GaAs Heterojunction Bipolar Transistors HBTs. This novel material combination will result in enhanced device performance. For HBTs, critical parameters affecting the device performance are base doping, base contact resistance, and band discontinuities at the emitter base junction. The semiconductor Ge has excellent potential to improve the performance of GaAsA1GaAs HBTs. The third investigates the current handling capability of A1GaAsGaAs HBTs. The idea is to use the HBT as a high- power and high-speed device. Multi-finger emitter and emitter ballasting resistor are used in the design of the HBT. The direct and resonant tunneling diode project used a k dot p band model to calculate the complex wave-vectors of the tunneling electrons in the calculation of the I-V characteristics of these types of diodes. Another important point in the calculation is the inclusion of semiconductor band-bending. jhd

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  • Solid State Physics

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