SOS/SOI optoelectronic switches: effects of ion-implantation and materials processing on nonlinear photoconductive response

The photocurrent from ultrafast photoconductive switches formed on SOS and SIMOX (separation by implantation of oxygen) wafers with microstrip transmission line technology has been measured. Some of these switches exhibit nonlinear response as a function of applied electrical bias and incident optical power. The nature of the observed behavior is critically dependent on the order of ion implantation and metallization processing steps during the fabrication procedure. Device characteristics are also dependent on the extent of damage induced by ion-implantation. Ion-implantation conditions were based on present models of metal-semiconductor contacts to optimize either linear or nonlinear photoconductive response of these switches. Beam currents were limited to 0.22 μA/cm² to limit the maximum wafer temperature during ion implantation to <60°C. Depth profiles of ion-implantation-induced damage were modeled using the TRIM-88 Monte Carlo calculation. Simulations of the vacancy and interstitial concentration as a function of depth were obtained both for single energy implants and the sum of multiple energy implants in SIMOX and SOS at various dosages. After implantation, damage-versus-depth profiles were measured with Rutherford backscattering spectroscopy, yielding a comparison of the state of amorphization and in situ recrystallization