Electron-beam fabricated titanium and indium tin oxide position-sensitive detectors

Abstract

This work reports on the development of an optical position sensitive detector (PSD) which exhibits highly linear output characteristics comparable to complex multilayer sensors and which is based on a simple, two-stage fabrication procedure. Further advantages of this device include the potential for large-area surfaces and the production of comparatively large output signals requiring no amplification or external biasing. Most of these studies were carried out on a Schottky barrier (SB) structure based on crystalline p-silicon and electron-beam evaporated titanium and operated under focused white light. As a comparison of output behaviour, a second testing run was carried out using a red laser diode. The devices had metal layer thicknesses ranging from 2000Å to 180Å and results showed that the highest sensitivities and lowest nonlinearities occurred with PSDs having thinner titanium films. The overall best results were obtained using white light in photovoltaic mode, i.e. with no external biasing. Additionally, we compared these titanium devices to electron-beam deposited indium tin oxide (ITO) devices, and found that the ITO series had much lower outputs and higher nonlinearities. These latter devices were considered to be heterojunction structures of n-ITO/p-Si.