Characterization and Modeling of Ion-Implanted Gallium-Arsenide Fet's.

Gallium Arsenide has several advantages compared to silicon such as high low-field mobility, large ((TURN)1.4 eV) and direct energy band gap. Fabrication of devices and IC's (Integrated Circuits) relies heavily on Semi-Insulating (SI) GaAs substrate. However, there are some undesirable properties associated with binary compound semiconductor. Because the physical properties (such as melting point) of Ga are quite different from those of As, GaAs has intrinsic defects and surface defects. This leads to GaAs material characteristics with large surface state densities and deep level traps in the bulk. This thesis investigates the non-ideal behavior of GaAs FET's (Field Effect Transistors) fabricated by ion-implantion into the GaAs substrate. In order to understand the behavior of ion-implanted into the GaAs FET's, a thorough understanding of the crystal properties is required. We start from the review of the crystal growth and imperfections related to the conditions of crystal growth. Then, the influence of these crystal imperfections on the device characteristics is discussed and a model based on the process parameters such as doses, projected range, etc., is developed. This model is used for the simulation of the FET's device parameters such as threshold voltage and transconductance as functions of the gate length, temperature, and orientation on the wafer. This model can also simulate the effect of annealing time on the FET characteristics. It can be used as a tool to optimize the process parameters before the actual fabrication. This work has been applied to GaAs MESFET (MEtal-Semiconductor Field Effect Transistor) and HIGFET (Heterostructure Insulated Gate Field Effect Transistor). However, it is also suitable for MODFET (MOdulation Doped Field Effect Transistor) as well as some other GaAs FET's.