The standard SPICE Gummel-Poon model for bipolar transistors in the case of current crowding is inaccurate at high frequencies primarily due to the position of the capacitances. An improved distributed bipolar transistor model is developed, with fractions of both the depletion and the diffusion capacitances placed outside the base spreading resistance and the transistor junctions. The model is contrasted with the standard model by comparing the high frequency characteristics for an HBT.

The instability of the electrical properties of semi-insulating GaAs materials has been investigated. The presence of chemical contaminants on the surface of the finished wafers is responsible. Simulated thermal conversion using intentional carbon-ion implantation indicates larger concentrations for the possible contaminants on the surface than that in the bulk. The contribution to instability due to preferential gettering of imperfections from bulk by the implant and annealing process was eliminated using intentional Ar-ion implantation. For the samples which exhibited a change in electrical conduction type, a linear relationship between the thickness of the type-converted surface layer and the square root of heat treatment time was observed. It is proposed that the causes for the instability are governed by conventional diffusion mechanisms with multiple electrically active species involved. A positive correlation was also observed between thermally induced electrical instability in ion-implanted material and a reduction in activation, peak carrier density, and Hall mobility.

An order of magnitude improvement in the specific contact resistance of gold-based ohmic contacts to p-type GaInAsP (Eg=1.13 eV) is reported. A novel technique using a silicon susceptor has been employed in a rapid thermal processor. A direct comparison between gold-based contacts annealed in a conventional furnace and the rapid thermal processor indicated a specific contact resistance of 4.2×10−5 and 4.1×10−6 Ω cm2, respectively. Auger electron spectroscopy, in depth profile mode, revealed two different metallurgical profiles for the conventional furnace and the rapid thermal processor. The rapid thermal processor was successfully implemented in a p-i-n optical detector process resulting in a reduction in the device series resistance and improved performance.